ENGINEERING RESEARCH INSTITUTE THE UNIVERSITY OF MICHIGAN ANN ARBOR Final Report AN INVESTIGATION OF INTERGRANULAR OXIDATION IN STAINLESS STEELS AND HIGH-NICKEL ALLOYS WADC Technical Report 55-470 Part 2 Clarence A. Siebert Maurice J. Sinnott Lynn H. DeSmyter Harry M. Ferrari Materials Laboratory Project 2110 UNITED STATES AIR FORCE WRIGHT AIR DEVELOPMENT CENTER AIR RESEARCH AND DEVELOPMENT COMMAND WRIGHT-PATTERSON AIR FORCE BASE, OHIO CONTRACT NO. AF 33(616)-353, PROJECT NO. 54-670-60 July 1956

FOREWORD This report was prepared by The University of Michigan, under USAF Contract No. AF 33(616)-353. The contract was initiated under Project No. 54-670-60, and was administered under the direction of the Materials Laboratory, Directorate of Research, Wright Air Development Center, with Lt Richard Agricola acting as project engineer. WADC TR 55-470 Pt 2 iii

ABSTRACT Specimens from Chromel ASM, Hastelloy B, and commercial and vacuum-melted type 310 alloys were oxidized for 100-hour periods in the stressed condition. Intergranular oxidation measurements were obtained microscopically. In general, the intergranular penetrations increased rapidly with stress after a certain minimum value was reached. This minimum value, denoted as the threshold stress, was determined for each alloy at various temperatures. The weight gained during oxidation was determined. It was found that most of the alloys tested followed the parabolic oxidation law. PUBLICATION REVIEW This report has been reviewed and is approved. FOR THE COMMANDER: M, R. WHITMORE Technical Director Materials Laboratory Directorate of Research WADC TR 55-470 Pt 2 iv

TABLE OF CONTENTS Page LIST OF TABLES vi LIST OF FIGURES vii INTRODUCTION 1 EQUIPMENT 1 PROCEDURE 2 Specimen Preparation 2 Operating Procedure2 Evaluation of Specimens 2 Metallographic Studies 3 MATERIAL 3 RESULTS AND DISCUSSION 3 Weight-Gain Investigation4 Stress-Oxidation Investigations4 Chromel ASM5 Commercial Type 310 Alloy, Heat 25139 6 Hastelloy B, Heat B-1400 7 Vacuum-Melted Type 310 Alloy, Heat 4X-343 8 Metallographic Examination 9 SUMMARY AND CONCLUSIONS 10 BIBLIOGRAPHY 10 WADC TR 55-470 Pt 2 v

LIST OF TABLES No. Page I. Chemical Analyses of Materials, Weight Percent 11 II. Parabolic Rate Constants Obtained from Weight-Gain Oxidation in (mg/in.2) (1/min). 11 III. Results of Stress-Oxidation on Chromel ASM 12 IV. Results of Stress-Oxidation on Type 310 Alloy, Heat 25139 12 V. Results of Stress-Oxidation on Hastelloy B, Heat B-1400 13 VI. Results of Stress-Oxidation on Type 310 Alloy, Heat 4X-343 13 WADC TR 55-470 Pt 2 vi

LIST OF FIGURES No. Page 1. Photomicrograph. Fissuring type 1. 14 2. Photomicrograph. Fissuring type 2. 14 3. Photomicrograph. Fissuring type 3. 14 4. Photomicrograph. Fissuring type 4. 14 5. Photomicrograph. Fissuring type 5. 15 6. Photomicrograph. Fissuring type 6. 15 7. Photomicrograph. Fissuring type 7. 15 8. Photomicrograph. Fissuring type 8. 15 9. Graph. Square of specific weight gain vs time; Chromel ASM alloy. 16 10. Graph. Square of specific weight gain vs time; type 310 alloy, heat 25139. 16 11. Graph. Square of specific weight gain vs time; Hastelloy B, heat B-1400. 17 12. Graph. Square of specific weight gain vs time; type 310 alloy, heat 4X-345. 17 13. Graph. Penetration vs depth below surface. Chromel ASM alloy, 1700~F. 18 14. Graph. Penetration vs depth below surface. Chromel ASM alloy, 1800~F. 18 15. Graph. Penetration vs depth below surface. Chromel ASM alloy, 1900~F. 19 16. Graph. Penetration vs depth below surface. Chromel ASM alloy, 2000~F. 19 17. Graph. Summary penetration-frequency curves. Chromel ASM alloy, 1700~F. 20 WADC TR 55-470 Pt 2 vii

LIST OF FIGURES (Continued) No. Page 18. Graph. Summary penetration-depth curves. Chromel ASM alloy, 1700~F. 20 19. Graph. Summary penetration-frequency curves. Chromel ASM alloy, 1800~F. 21 20. Graph. Summary penetration-depth curves. Chromel ASM alloy, 1800~F. 21 21. Graph. Summary penetration-frequency curves. Chromel ASM alloy, 1900~F. 22 22. Graph. Summary penetration-depth curves. Chromel ASM alloy, 1900~F. 22 23. Graph. Summary penetration-frequency curves. Chromel ASM alloy, 2000~Fo 23 24. Graph. Summary penetration-depth curve. Chromel ASM alloy, 2000 ~F 23 25. Graph. Penetration vs depth below surface. Type 310 alloy, heat 25139, 1700~F. 24 26. Graph. Penetration vs depth below surface. Type 310 alloy, heat 25139, 1800~F. 24 27. Graph. Penetration vs depth below surface. Type 310 alloy, heat 25139, 1900~F. 25 28. Graph. Penetration vs depth below surface. Type 310 alloy, heat 25139, 2000~F. 25 29. Graph. Summary penetration-frequency curves. Type 310 alloy, heat 25139, 1700~F. 26 30. Graph. Summary penetration-depth curves. Type 310 alloy, heat 25139, 1700~F. 26 31. Graph. Summary penetration-frequency curves. Type 310 alloy, heat 25139, 1800~F. 27 32. Graph. Summary penetration depth curves. Type 310 alloy, heat 25139, 1800~F. 27 WADC TR 55-470 Pt 2 viii

LIST OF FIGURES (Continued) No. Page 33. Graph. Summary penetration-frequency curves. Type 310 alloy, heat 25139, 1900~F. 28 34. Graph. Summary penetration-depth curves. Type 310 alloy, heat 25139, 1900~F. 28 35. Graph. Summary penetration-frequency curves. Type 310 alloy, heat 25139, 2000~F. 29 36. Graph. Summary penetration-depth curves. Type 310 alloy, heat 25139, 2000~F. 29 37. Graph. Penetration vs depth below surface. Hastelloy B, heat B-1400, 1200~F. 50 38. Graph. Penetration vs depth below surface. Hastelloy B, heat B-1400, 1400~F. 30 39. Graph. Penetration vs depth below surface. Hastelloy B, heat B-1400, 1600~F. 31 40. Graph. Penetration vs depth below surface. Hastelloy B, heat B-1400, 1800~F. 31 41. Graph. Summary penetration-frequency curves. Hastelloy B, heat B-1400, 1200~F. 32 42. Graph. Summary penetration-depth curves. Hastelloy B, heat B-1400, 1200~F. 32 43. Graph. Summary penetration-frequency curves. Hastelloy B, heat B-1400, 1400~F. 55 44. Graph. Summary penetration-depth curves. Hastelloy B, heat B-1400, 1400~F. 55 45. Graph. Summary penetration-frequency curves. Hastelloy B, heat B-1400, 1600~F. 54 46. Graph. Summary penetration-depth curves.~ Hastelloy B, heat B-1400, 1600~F. 54 47. Grapho Summary penetration-frequency curves. Hastelloy B, heat B-1400, 1800~F. 55 WADC TR 55-470 Pt 2 ix

LIST OF FIGURES (Continued) No. Page 48. Graph. Summary penetration-depth curves. Hastelloy B, heat B-1400, 1800~F. 35 49~ Graph. Penetration vs depth below surface. Type 310 alloy, heat 4X-343, 1900~F. 36 50. Graph. Penetration vs depth below surface. Type 310 alloy, heat 4X-343, 2000~F. 36 51. Graph. Summary penetration-frequency curves. Type 310 alloy, heat 4X-343, 1900~F. 37 52. Graph. Summary penetration-depth curves. Type 310 alloy, heat 4X-343, 1900~F. 37 53. Graph. Summary penetration-frequency curves. Type 310 alloy, heat 4X-343, 2000~F. 38 54~ Graph. Summary penetration-depth curves. Type 310 alloy, heat 4X-343, 2000~F. 38 55. Photomicrograph. Chromel ASM alloy, as received. 39 56. Photomicrograph. Type 310 alloy, heat 25139, as received. 39 57. Photomicrograph. Hastelloy B alloy, heat B-1400, as received. 39 58. Photomicrograph. Type 310 alloy, heat 4X-343, as received. 39 59. Photomicrographo Type 310 alloy, heat 25139, 1700~F, stress 2245 psi, 100x. 40 60o Photomicrograph. Type 310 alloy, heat 25139, 1800~F, stress 1580 psi, lOOx. 40 61. Photomicrograph. Type 310 alloy, heat 25139, 1900~F, stress 755 psi, lOOx. 40 62. Photomicrograph. Type 310 alloy, heat 25139, 2000~F, stress 755 psi, 100x. 40 63. Photomicrograph. Hastelloy B, heat B-1400, 1200~F, stress 1925 psi, 100x. 41 WADC TR 55-470 Pt 2 x

LIST OF FIGURES (Concluded) No. Page 64. Photomicrograph. Hastelloy B, heat B-1400, 1400~F, stress 10,000 psi, 75x. 41 65. Photomicrograph. Hastelloy B, heat B-1400, 1600~F, stress 7800 psi, 100x. 41 66. Photomicrograph. Hastelloy B, heat B-1400, 1800~F, stress 4180 psi, 100x. 41 67. Photomicrograph. Type 310 alloy, heat 4X-343, 1900~F, stress 750 psi, 100x. 42 68. Photomicrograph. Type 310 alloy, heat 4X-343, 2000~F, stress 600 psi, 100x. 42 69. Photomicrograph. Chromel ASM alloy, 2000~F, stress 750 psi, 100xo 42 70. Photomicrograph. Type 310 alloy, heat 25139, 1900~F, stress 1096 psi, 100 x.42 WADC TR 55-470 Pt 2 xi

INTRODUCTION When a metal is subjected to an oxidizing medium the usual result is the formation of a continuous oxide layer on the exposed surface. In general, the oxide layer increases in thickness with increasing time and/or temperature of exposure. With some alloys, however, oxidation also occurs in the grain boundaries ahead of the metal-oxide interface. This report is primarily concerned with this grain-boundary oxidation, although the volume or lattice oxidation rate will affect the measured grain boundary and, therefore, must be considered as wello Intergranular oxidation becomes an important factor in applications where thin sections are exposed to air at high temperatures. Under these conditions, the portion of the metal influenced by these oxide fissures is a significant percentage of the whole and may result in premature failure. The present program arose from the need of the U. S. Air Force for information concerning intergranular oxidation in stainless steels and high-nickel alloys at high temperatures, There were three objectives in this research program: 1. to investigate the effect of temperature and stress on the progressive intergranular oxidation and to determine the threshold stress of some stainless steels and high-nickel alloys at temperatures of 1200~F and above, 2. to measure the oxidation rates of these materials by means of the weight gained during oxidation, and 3. to study the subsurface oxides. EQUIPMENT The equipment used during this investigation was the stress-oxidation and continuous weight-gain apparatus described in WADCTR 55-470 Pt 1. Another stressoxidation unit similar to those described in the above report was constructed. WADC TR 55-4T70 Pt 2 1

PROCEDURE Specimen Preparation The specimens for the stressed-oxidation tests were prepared as standard strip specimens having a 1/2 x 2-inch gauge portionn A detailed description of the specimen was given in the previous report (1)o The specimens for the weight-gain measurements were 2 x 1-inch rectangles of the as-received material containing a 1/64-inch hole near the top for the insertion of the platinum suspension wire. Operating Procedure The oxidation procedure for the stressed-oxidation tests was the same as that used during the previous investigation (1), except that the specimens were not quenched but air-cooled. Since x-ray analysis of the oxides was no longer a regular part of the investigation, this simplification was possible. The weight-gain procedure was the same as that described in the previous report. The metallographic polishing procedure also was the same as that used previously. Evaluation of Specimens The polished specimens were measured to determine the extent of intergranular penetration. The mean depth (x) and the total number of penetrations (N) were then determined from the penetration measurements. A complete description of the method of taking and evaluating penetration data is given in WADC TR 54-120 (2). In brief, the method consisted of examining the polished specimen at 500 diameters, using a calibrated, No. 6 grain-size eyepiece. The grid, containing 6 squares in the side, was aligned with the specimen edge, and the number of penetrations and their depths were obtained by traversing the edge over a distance of approximately 2 inches. In addition to the procedure used in the previous years (1,2), another method of evaluating and presenting the penetration data was usedo Repeated measurements on the same specimen showed that the most uncertain types of penetrations are the extremely small ones, ie., the ones which lie in the first group. Generally these represent true intergranular penetrations, as is shown by high-magnification examination. However, some are the result of polishing artifacts or are surface-roughness effects which usually occur during oxidation. WADC TR 55-470 Pt 2 2

In addition to being somewhat uncertain, these small penetrations dominate the evaluation with respect to total number and mean depth, since they are present to a greater extent than the deeper ones. To make the effect of stress and temperature on the deeper and more significant penetrations more noticeable, it was decided to make a modified number and mean-depth calculation, excluding the smaller penetrations. To do this the first group, and in a few instances the first and second groups, was excluded and a modified number and mean-depth calculation made. This new method shows the changes in the penetration character in the critical regions to a more marked extent. Metallographic Studies In conjunction with the penetration studies described above, each specimen was carefully examined metallographically, using the optical microscope. The specimens which exhibited the phenomenon called "fissuring" were classified according to the degree to which this fissuring was observed. Figures 1 through 8 were given the arbitrary designations one through eight, from smaller to greater fissuring, and were used to give a numerical value to the extent of fissuring on all samples that exhibited the phenomenon. The numeral "zero" was used to designate specimens which exhibited no fissuring. The specimens were also examined for any changes in microstructure which might occur during testing. MATERIAL The materials used in this investigation consisted of specimens from Chromel ASM alloy, heat 25139 of commercial type 310 alloy, heat B-1400 of Hastelloy B, and heat 4X-343 of vacuum-melted type 310 alloy. The type 310 stainless alloys and the Chromel ASM alloy were received in the form of cold-rolled and annealed strip 1.0 x 0.5 inchPand the Hastelloy B in the form of hot-rolled strip 1.0 x 0.38 inch, which h.ad received a light cold-roll pass to improve the surface, and a final anneal. The chemical analyses of the heats are presented in Table I. RESULTS AND DISCUSSION For purposes of discussion this section has been divided into three parts, namely: (1) weight-gain investigation, (2) stress-oxidation investigation, and (3) metallographic investigation. WADC TR 55-470 Pt 2.

Weight-Gain Investigation A visual study of the depth of intergranular oxidation at high temperatures is of limited value by itself. Some knowledge of the volume of oxidation should also be known before an alloy can be properly evaluated, since an apparently low rate of intergranular penetration may result from a high-volume oxidation. A continuous weight-gained measuring apparatus has been used for measuring oxidation rates. It should be noted that the weight gained during oxidation is a measure of both the lattice and the intergranular oxidation; however, the intergranular oxidation probably is a smailL contributing factor compared to the lattice oxidation. The experimental data, when plotted as square of the weight gained vs time, are linear, as shown in Figs 9 through 12. Most samples show some deviation from the parabolic oxidation law in the early stages, as can be seen from the fact that the linear plots do not go through the origin. This initial deviation is usually found in oxidation studies, and the theoretical reasons for its occurrence have been stated by Gulbransen and Andrew (3). Because of these deviations which occur at the initial stages of testing, the parabolic rate constant (slope of AW2-,vs-time curve) is probably a better indication of the volume oxidation than the,pecific weight gained after a given time. Figures 9 through 12 are plots of weight gained squared vs time for the four alloys investigated, and Tabie 4II is a summary of the parabolic weightgained constants. The rate constant of the Chromel ASM alloy at 1800~, 1900~, and 2000~F is lower than the rate constants of any of the other alloys investigated. The Hastelloy B has a much greater rate of oxidation than the other alloys investigated, and at 1600~ and 1800~F the rate constant is 0.047 and 0356, respectively, the latter being almost tenfold greater than any value obtained on any of the other alloys tested. This factor, combined with the fact that the oxide layer flakes off during cooling, woLAld limit the use of this material in this temperature range. Stress -Oxidation Investigations Several alloys have been investigated at varying stresses and temperatures for the determination of their intergranular oxidation characteristics under stress, The stress levels were chosen so as to give a representative count of intergranular penetration in the low stress regions and were concentrated in the region where the stress caused an increase in the intergranular penetration. The object was to locate the test points near, but not in, the region where fissuring throughout occurred, i.e., fissuring to the extent shown in Figs, 5 through 8. Since each material has its own characteristic attributes, the alloys will be considered individually. WADC TR 55-470 Pt 2 4

Chromel ASM The Chromel ASM alloy was tested at various stress levels at temperatures of 1700~, 1800~, 1900~, and 2000~Fo This alloy proved to be difficult to evaluate because of a large number of small penetrations and because of a precipitate throughout the matrix which at times appeared to be intergranular penetrationo The great number of shallow entries is thought to be the result of a surface skin of fine grains present in the as-received material, as shown in Fig. 55. This alloy had approximately double the total number of penetrations of any other alloy testedo The variation in the number of intergranular penetrations with depth below the metal interface at constant temperature is given in Figs. 15 through 16. These curves follow the general decay-type curve as described in WADC TR 54-120, Figures 17 through 24 show the variation in mean depth (x) and number (N) of intergranular penetrations with stress at temperatures of 17000, 18000, 19000, and 2000~F. The number of penetrations is the total number counted per inch, and the mean depth is an average depth of penetrationo These parameters are discussed in detail in WADC TR 54-120. In addition, as described in the procedure section of this report, another method of presenting the data was used. Modified number and mlean-depth curves excluding all the small penetrations which fall in the first group, and in some instances excluding the first and second groups, are presented in some of the graphso As can be seen in Figs. 19 through 24 these modified curves tend to follow the elongation curve more closely and exhibit a more marked. change in penetration characteristics as the threshold stress is approached. The elongation curves, which are plotted on these graphs, represent the permanent elongation, as measured at room temperature after the stress had been relieved. Because all the penetrations shallower than the first group (0.00059 inch) are placed in the same class, there exists a minimum value of mean depth which can be obtained. This value is shown as a dotted line on some of the mean-depth graphs. Figures 17 and 19, illustrating the variation in penetration number with stress at temperatures of 1700~ and i800~F, show an initial increase in number, followed by a decrease in number, as the stress is increasedo At 1900~ and 2000~F the number increases with no increasing stress as shown in Figso 21 and 23. No explanation for the above behavior can be offered at this time. When the small penetrations are eliminated, the number of penetrations increases slowly at first as the stress is increased, and then increases abruptly as the threshold stress is reached at 1800~, 19000, and 2000F. These modified curves tend to follow the elongation curves and appear to be more significant than the regular curves. Figures 18, 20, 22, and 24, illustrating the effect of stress on the mean depth at constant temperature, show a more or less constant mean depth with increasing stress, until a critical region is reached where the mean depth increases. The extent of this increase is a function of the testing temperature. WADC TR 55-470 Pt 2

Figures 18 and 20 show that the mean depth of penetration is but little affected by stress in the 1700~ and 1800~F samples. The 1900~ and, to a greater extent, the 2000~F specimens, however, reveal in Figs. 22 and 24 that a significant increase in the mean depth occurs when this critical stress level is reached. The modified curves appear to show a constant mean depth as stress increases until the threshold stress is reached, then the mean depth increases very sharply. The elongation of the specimen seems to have a profound effect on the intergranular penetration. In the 1700~ and 1800~F tests the elongation reaches a value of only 2-5% when the material begins to fissure throughout. However, in the 1900~ and 2000~F specimens the fissuring throughout did not occur until the elongation had reached a value of approximately 8% in the 1900~F specimens and 30% in the 2000~F specimens. Since these latter temperatures were the ones which showed the greatest increase in penetration, it is possible that the elongation itself is a major factor, or that it is but a measure of the intensity of circumstances which cause this increase in penetration depth. As outlined in the introduction, one of the objects of this investigation is to determine the threshold stress, i.e., the stress at a given temperature where a material begins to exhibit a sharp increase in intergranular penetration. For the Chromel ASM alloy this stress corresponds very closely to the stress at which the elongation greatly increases. This can be seen in Figs. 17 through 24 as a large change in slope in the elongation-vs-stress curve. Of course, the value of this threshold stress is somewhat arbitrary and is a function of what is considered to be a significant increase. In this case the beginning of the sharp increase in penetration depth was considered to be the threshold stress. For the Chromel ASM alloy these stresses were found to be 2000, 1400, 900, and 600 psi at temperatures of 1700~, 1800~, 1900~, and 2000F, respectively. The data obtained from the stress investigation for the Chromel ASM alloy are summarized in Table III. Commercial Type 310 Alloy, Heat 25139 The variation in the number of intergranular penetrations with depth below the oxide surface at constant testing temperatures is given in Figs. 25 through 28. These curves follow the general decay type as described in WADC TR 54-120. As the temperature of testing is increased, the number of deep penetrations increases. When the stress at a given temperature is increased, the number of deep penetrations also increases. Figures 29 through 356 are the penetration-number and mean-penetrationsdepth graphs. The elongation is plotted for all samples tested in both types of graphs, although it was impossible to obtain penetration data on some of the more highly stressed samples since they contained fissures throughout the matrix. In the 1700~, 18000, and 2000~F tests the number decreases as the stress is increased when all groups are considered. However, the number of WADC TR 55-470 Pt 2 6

deep penetrations is increased when the minor groups are excluded. In Fig. 29 (17000F) the curve excluding the first group showed an increase in penetration number with increasing stress, while the 1800~ and 20000F graphs showed a decrease even when the first group was excluded, as shown in Figs. 31 and 35. Excluding the first and second groups showed no appreciable effect of stress on number in the 1800~ and 2000~F graphs. Figure 33 (1900~F) shows an increase in the number of penetrations for the total number as well as for the condition when the minor groups are excluded. Figures 30 and 34 show that the mean depth considering all penetrations, increases significantly in the 1700~ and 1900~F tests, and this is noticeable when the first group is omitted. The 1800~F graph shows a shift in the shape of the curve as the number of groups considered is decreased. Considering all groups, the mean depth decreases slightly, while excluding the first group shows no effect of stress, and excluding the first and second groups shows a significant increase in the mean depth. It was estimated that the threshold stresses occur at 2300, 1400, 900, and 600 psi at temperatures of 1700~, 1800~, 1900~, and 2000~F. The data obtained from the stress investigation for commercial 310 alloy are summarized in Table IV. Hastelloy B, Heat B-1400 The Hastelloy B material was tested at temperatures of 1200~, 1400~, 1600~, and 1800~F in the stress-oxidation units. Figures 37 through 40 are the penetration-frequency graphs giving the relationship between penetration depth and number. These curves are of the decay-curve type previously discussed. The effect of stress in the critical region (that region where the material elongates considerably) could not be determined for the 12000F tests since the units were not constructed to carry a load greater than 200 lb. A 1/4-inch-wide section was the smallest practical specimen size, and therefore the maximum stress obtainable to produce much elongation was about 20,000 psi, which was insufficient. The testing at 12000F was therefore discontinued when 20,000 psi showed negligible elongation at the end of the test. Figures 41 through 48 show the effect of stress on the number and mean depth of penetrations. The 12000F tests were conducted at a stress below the critical range, as previously discussed, and therefore do not show any appreciable effect. Since all the penetrations encountered were extremely small, the slight increase in number is not considered significant. The large amount of scatter encountered in the 14000F curve makes the effect of stress on number difficult to determine, while the 1600~F shows an increase and the 1800~F a slight decrease in number. Excluding the first group shows an increase in the number of deep penetrations in the 1800~F graph. This exclusion is of no value in the lower-temperature tests since the penetrations are for the most part in the first group. The mean depth of penetration is not appreciably affected by WADC TR 55-470 Pt 2 7

stress in the 1200~, 1400~, and 1600~F tests as shown in FigSo 42, 44, and 46. In the 1800~F tests, however, the mean depth is increased significantly with increasing stress. This is especially noticeable in the deeper penetrations, as is shown by the curves excluding the minor groups. It was not possible to obtain a great deal of elongation in the 18000F tests. Some specimens, which fractured during the latter part of the test, showed only 3.55 elongation. The threshold stresses were estimated as occurring at stresses of 15000, 6000, and 5500 psi for temperatures of 1400~, 16000, and 1800~F, respectively. This latter value at 1800~F is more than twice as great as values obtained for either Chromel ASM or the type 310 alloys for the same temperature. The data obtained from the stress investigation for the Hastelloy B are summarized in Table V. Vacuum-Melted Type 310 Alloy, Heat 4X-343 This alloy was tested only at 1900~ and 20000F because of limited time. Figures 49 and 50 show the penetrations-vs-depth curves at various stress levels. Again, the curves are of the decay type. Figures 51 through 54 show the effect of stress on the number and mean depth of penetrations. The number of penetrations appears to be independent of the stress at both 1900~ and 2000~F when all groups are considered. At 1900~F, when the first group is excluded, the number still remains approximately constant, but excluding both the first and second groups shows an increase in number with increasing stress at 2000~F. The mean depth at 1900~F remains approximately constant as a function of stress when all groups are considered, and also when the minor groups are excludedo At 2000~F the mean depth remains fairly constant at first, and then increases as the critical region is reached. The reason why the mean depth at 1900~F does not show an increase is that the critical region has not quite been reached, as can be seen from the fact that at the highest stress tested the sample just barely showed enough fissures to be classified in fissuring class No. 1. Apparently at this temperature the elongation increases considerably before the alloy exhibits any fissuring. Approximate values for the threshold stresses in this alloy are 900 and 650 psi at temperatures of 1900~ and 2000~F, respectively. This vacuum-melted alloy has intergranular penetration characteristics which are comparable to that of the commercial type 310 alloy. The data obtained from the stress investigation for the vacuum-melted 310 alloy are summarized in Table VIo WADC TR 55-470 Pt 2 8

Metallographic Examination Photomicrographs of each of the four alloys in the as-received condition are presented in Figs. 55 through 58. These phogomicrographs were taken to provide a standard of reference for photomicrographs taken following testing. Figure 55 illustrates the surface layer of small grains which is present in the as-received Chromel ASM alloy. The commercial type 310 alloy has a twinned, medium-sized grain structure. Examination at l000x shows the presence of a discontinuous grain-boundary carbide network. The Hastelloy B material in the as-received condition has a banded structure of two rows of large grains at the center with fine grains on either side of the bands, as shown in Fig. 57. The as-received vacuum-melted type 310 alloy has a grain structure similar to that of the commercial 310 alloy, except that examinination at 1000x shows a more continuous carbide network in the grain boundaries. After testing, the Chromel ASM alloy still exhibits the fine-grained surface layer. Considerable grain growth occurs at 2000~F, as can be seen by comparing Fig. 69 with 55; however, the surface layer still remains much finer than the matrix. Type 310 alloy, heat 25139, exhibits no grain growth at 1700~ and 1800~F, but does exhibit appreciable grain growth at 1900~ and2O000F, as can be seen by comparing Figs. 59 throughl62 with Fig. 56. The final grain size at any given temperature is practically independent of the applied stress. The final structure after testing is generally quite similar to that in the as-received condition. The appearance of a new phase is detected only when stresses sufficiently high to cause much "fissuring" are used. At these high stresses, the appearance of an excess phase, as shown in Fig. 70, occurs. Microhardness impressions indicate that the excess phase is much harder than the matrix. Although it has not been positively established, it is thought that this phase is a high nitrogen-chromium compound. A similar phase found in creep-rupture specimens of 18-8 stainless steel was identified as a high nitrogen phase by Smith (4). The banded structure of the Hastelloy B material in the as-received condition appears to be minimized after heating for 100 hours at the testing temperatures, as shown in Figs. 63 through 66. The vacuum-melted type 310 alloy exhibits very little grain growth at 1900~ and 2000~F (Figs. 67 and 68) compared to the as-received condition (Fig. 58). No phase changes were detected during testing in this vacuum-melted alloy; however, it is possible that an excess phase similar to that shown in Fig. 70 for the commercial 310 alloy might occur if sufficiently high stresses were used to cause "fissuring." WADC TR 55-470 Pt 2 9

SUMMARY AND CONCLUSIONS 1. The weight gained at various time intervals during oxidation was determined for Chromel ASM, Hastelloy B, and commercial and vacuum-melted type 310 alloys at temperatures varying from 1200~ to 2000~F. Most of the alloys tested followed the parabolic oxidation law. The parabolic rate constant was determined for each specimen investigated. 2. The Chromel ASM alloy had the lowest and the Hastelloy B the highest parabolic rate constants of the alloys tested. The commercial and the vacuummelted 310 alloys had approximately the same parabolic rate constants. 35. Chromel ASM, Hastelloy B, and commercial and vacuum-melted type 310 alloys were oxidized at various stress levels for 100-hour periods at temperatures ranging from 1200~ to 2000~F. Intergranular penetration measurements were made and the data presented as follows: (1) penetration frequency vs depth, (2) penetration number (N) vs stress, and (3) the mean depth (x) vs stress. 4. The threshold stress, i.e., the stress at which a sharp increase in depth of intergranular penetrations occurs, was determined for each alloy at various temperatures. At 1900~ and 2000~F, the threshold stress occurred at approximately the same value for the Chromel ASM alloy, commercial type 310 alloy, and the vacuum-melted 310 alloy. BIBLIOGRAPHY 1. Siebert, C. A., Sinnott, M. J., Keith, R. E., and DeSmyter, L. H., An Investigation of Intergranular Oxidation in Stainless Steels and High-Nickel Alloys, WADC TR 55-470 Pt 1, April, 1955. 2. Siebert, C. A., Sinnott, M. J., and Keith, R. E., An Investigation of Intergranular Oxidation in Stainless Steels, WADC TR 54-120, January, 1954. 3. Gulbransen, E. A., and Andrew, K. F., J. Electrochem. Soc., 98, 241 (1951). 4. Smith, G. V., Dulis, E. J., and Houston, G. E., Trans. ASM, 42, 935 (1950). WADC TR 55-470 Pt 2 10

TABLE I jg~~~~j~~ ~~~CHEMICAL ANALYSIS OF MATERIALS, WEIGHT PERCENT Alloy and Heat No. Fe Ni Cr Mn Si C S P Co Mo V \1 -q Chromel, ASM 0.37 77.65 19.81 0.30 1.43 0.05 -- o 1T Type 310, 25139 Bal 19.26 25.42 1.58 0.62 0.05 --- astelloy B 0.26 0 0.24 0.0 ----- ----- 0.74 28.01 0.4 Hastelloy B 5.19 0.26 0.60 0.24 0.03 0.74 28.01 0.45 Type 310, 4X-343* Bal 20.35 25.14 1.87 0.63 0.147 0.029 0.021 ---- *Vacuum-melted heat. TABLE II PARABOLIC RATE CONSTANT OBTAINED FROM WEIGHT-GAIN OXIDATION STUDIES IN (mg/in.2)(1/min) Oxidizing mOxidizing e r C e A Type 310 Alloy Hastelloy B Type 310 Alloy Temp'erature Chromel ASM Temperature Chromel ASM Heat 25139 Heat B-1400 Heat 4X-343 (OF) 1200 0.0012 1400 0.025 1600 0.047 1700 0.0027 1800 0.000133 0.0053 0.36 1900 0.0005 0.017 0.019 2000 0.00183 0.043 0.045

TABLE III TABLE IV RESULTS OF STRESS-OXIDATION ON CHROMEL ASM ALLOY RESULTS OF STRESS-OXIDATION ON TYPE 310 ALLOY, HEAT 25139 Including Excluding Excluding Including Excluding Excluding O'~ ~ Temp. Stress Elong. All Groups Group I Groups I and II Fissuring Temp. Stress Elong. All Groups Group I Groups I and II Fissuring (~F) psi * Class (~F) psi Class >^-3~~ _____N i x 103r N x x 1032 N N i x 103N N x x 102 Number \Ji 1700 ---- --- 1645 0.301 2 0.880 ----- ----- 1700 975 1.0 1912 0.351 88 0.921 6 1.480 0 U\J 1150 0 3164 0.306 31 0.880 ----- -- 2000 1.0 1615 0.317 47 0.880 ----- ---- o ~1 1535 0 3299 0.302 14 0.880 --- -- 0 2245 2.5 1448 0.310 25 O.880 ---- -- _**, ~ 2000 0.5 2034 0.317 59 0.886 0.6 1.480 0 2350 5.0 2054 0.15 51 0.886 0.5 1.480 0 0 2100 1.0 3019 0.304 23 0.880 -- ---- 2385 5.5 1484 0.330 76 O.880 ----- ---- 2150 1.5 3363 0.358 23.880 -- ----- 0.1-d~~~~~ *-~ ~2420 6.0 1427 0.313 32 O.880 ----- - - &F 2200 2.5 2712 0.303 16 o.880 - 2500 7.0 2468 0.391 233 0.993 36 1.609 0 2210 12.0 Fiss Fiss --- ---- - -5 2550 6.0 1207 0.323 461 O.893 1 1.480 0 FO 2240 6.5 Fiss Fiss --- - - - -- 5 2610 7.5 1294 0.323 45 0.957 3.5 1.885 0 2250 24.0 Fiss Fiss -- ----- ----- --- 8 2710 12.0 1252 0.473 199 1.384 89 2.009 0 2490 22.5 Fiss Fiss --- ----- ----- ----- 7 2880 16.0 Rupt Rupt --- ----- - --- 7 1800 750 0 1780 0.473 531 0.880 ----- ---- 0 1000 3.5 1772 0.497 601 O.880 O.5 1.480 0 1800 0 --- 2957 0. 11 55 0.880 ----- ---- 0 1065 3.5 1687 0.503 589 0.882 2 1.480 0 405 0 1876 0.306 18 O.880 ----- ---- 1300 8.5 1699 0.488 546 0.884 4 1.480 0 960 0 3279 0.313 72 0.897 2 1.480 0 1395 23.5 1782 0.659 683 1.236 204 2.072 3-4 1250 1.5 2278 0.300 1 0.880 ----- --- - 1400 14.0 ---- ----- --- ----- ----- ----- 1500 1.5 2419 0.304 15.880 ----- ----- 1520 3.5 3012 0.361 176 0.944 15 1.636 0 1500 8.0 1428 0.465 406 1.881 1 1.480 0 1550 6.0 1342 0.449 340 0.888 4.5 1.544 0 1550 5.5 2736 0.375 228 0.908 9.8 1.527 0 1580 43.0 Fiss Fiss --- ----- - - ---- 7 1560 4.5 2861 0.319 93 0.898 2.4 1.577 0 1580 6.0 1433 0.428 315 0.884 2 1.480 0 1600 18.0 Fiss Fiss --- - ---- 5-6 1690 12.0 1196 0.441 254 0.961 22.1 1.818 2 1600 15.0 Fiss iss --- ----- ----- ---- 6 1800 37.0 Fiss Fiss --- ----- --- DO3 ~ 1750 19.0 Fiss Fiss --- ----- ----- ----- 8 2000 28 Fiss Fiss --- ----- ----- ----- 8 1900 395 1.5 - --- 755 5.5 1622 0.454 429 0.898 13 1.480 0 1900 0 ---- 2634 0.344 157 0.880 ----- - - 0 900 12.5 1872 0.490 562 0.933 42.6 1.582 0 400 0 1762 0.358 175 0.887 2 1.480 0 952 14.0 1329 0.466 346 0.917 17.5 1.613 0 750 1.0 2091 0.317 63 0.880 ----- ----- 1010 15.0 1790 0.504 580 0.932 44 1.559 0 750 2.0 2448 0.448 586 0.917 56 1.480 0 1000 6.0 2309 0.395 514 0.973 35 1.715 0 1020 22.0 Fiss Fiss --- ----— 4 1060 6.5 2438 0.406 360 1.020 64.6 1.664 0 1050 31.0 1539 0.628 470 1.575 192 2.093 0 1075 3.0 3044 0.394 71 0.905 3 1.480 0 1100 28.0 Fiss Fiss --- ----- 7-8 1510 28.0 Fiss Fiss -- ----- 8 1100 6.0 1407 0.455 130. 949 15 1.569 0 2000 42.0 2225 0.922 1078 1.457 500 2.124 8 1105 8.5 2222 0.495 531 1.115 137 1.792 0 1120 13.0 3043 0.618 737 1.445 317 2.193 2 2000 300 1.5 2016 0.519 664 0.966 91 1.505 0 1125 16.5 Fiss Fiss --- ----- ----- ----- 4-5 500 3.5 1986 0.540 702 0.981 110 1.522 0 1250 29.0 Fiss Fiss --- --- ---- --- 8 570 4.0 1885 0.479 534 0.936 50 1.480 0 600 6.0 1664 0.503 521 0.950 61 1.480 0 2000 0 ---- 1648 0.472 271 0.913 14 1.521 0 620 6.0 1712 0.516 853 0.971 118 1.539 o 300 0.5 1910 0.430 369 0.960 47 1.505 0 650 7.0 1777 0.522 600 0.959 73.5 1.572 0 500 2.5 2019 0.426 401 0.937 36 1.512 0 755 8.5 1676 0.512 555 O.962 64.2 1.586 600 4.0 1062 0.476 225 0.999 381 1.584 0 650 6.0 1396 0.414 251 0.934 19 1.588 0 680 18.5 Fiss Fiss --- ----- ---- ----- 7 700 10.0 2518 0.657 721 1.394 276 2.222 2 750 22.0 Fiss Fiss --- ----- ----- --- 7 750 34.0 Fiss Fiss --- ----- ----- --- 8 750 10.0 2751 0.571 627 1.334 233 2.101 1 805 31.0 Fiss Fiss ----- 8 1000 55.0 Fiss Fiss -- ----- ----- ---- 8 * 0 designates no fissuring.

TABLE V TABLE VI RESULTS OF STRESS-OXIDATION ON HASTELLOY B, HEAT B-1400 RESULTS OF STRESS-OXIDATION ON TYPE 510 ALLOY, HEAT 4X-545 Tep.Including Excluding Excluding Fissuring Including Excluding Excluding Fissuring > Temp. Stress Elong. All Groups Group I Groups I and II Class Temp. stress Elong. All Groups Group I Groups I and II Class (OF) psi N x 10 N x x 103 N xxlO Number N xlO N xxlO N x 2 ^- 1200 2050 0 858 0.501 --- ----- ----- ----- 0 1900 500 2.4 1715 0.545 127 0.882 0.5 1.480 0 10250 0 975 0.502 -— 0 —--- ----- ----- 0 400 5.5 1672 0.545 124 0.882 0.5 1.480 0 J1 o15000 0 1210 0.505 -— 0 —--- ----- ----- 0 600 6.0 1687 0.520 58 0.880 -- ----- 0 19250 0 949 0.505 --- ----- ----- ----- 0 670 9.0 1659 0.557 105 0.880 --- ----- 0 F~~~~~- P-'~~~~~~~~~~~~~~~750 10.2 1740 0.547 140 0.885 0.7 1.480 0 o 1400oo 1000 0o ---- ----- --- ----- ----- ------ 0 4960 0 1077 0.500 --- ----- ----- ----- 0 750 10.2 1751 0.545 129 0.880 --- ----- 0 -d 5140 0 1517 0.500 --- --- ----- -— 0 850 15.5 1559 0.545 120 0.885 1.0 1.480 0 c+ 7470 0.5 969 0.500 --- ----- ----- ----- 0 900 18.5 1598 0.550 152 0.899 4.2 1.480 0 PQ 7775 0.5 788 0.501 --- ----- ----- ----- 0 950 14.5 1459 0.540 96 0.897 2.8 1.480 1 8180 0 1288 0.500 -— 0 —--- ----- ----- 0 8650 0.5 945 0.501 --- ----- ----- ----- 0 2000 200 1.6 1597 0.598 176 0.917 10.8 1.480 0 8900 0.5 860 0.500 --- ---— 5 —--- ----- 0 300 2.4 1557 0.5605 159 0.884 1.0 1.480 0 400 6.5 1708 0.555 161 0.882 0.5 1.480 0 10000 0.5 880 0.500 --- ----- ----- ----- 0 454 7.5 1518 0.33557 94 0.895 2.1 1.480 0 11800 1.5 686 0.500 --- ----- ----- ----- 0 500 11.5 1700 0.568 195 0.901 6.8 1.480 0 15700 2.0 1080 0.506 --- ----- ----- ----- 0 16go900 1.5 693 0.5053 --- ----- ----- ----- 0 600 ---- 1657 0.4o6 210 0.93355 17.4 1.497 0 17700 5.5 1548 0.508 — 0 —--- ----- ----- 650 15.0 1709 0.562 176 0.905 7.4 1.480 0 19000 7.0 1546 0.512 --- ----- ----- ---— 689 15.5 1557 0.404 255 0.956 18.5 1.665 0 720 12.0 1675 0.582 219 0.925 15.2 1.526 1 )- 1600 1000 0 722 0.500 --- ---— 0 —--- ----- 0 750 25.2 1501 0.589 185 1.027 25.5 1.957 1 5000 0 707 0.500 —- ---— _ —-— _ —--- ________________________ 5580 0 784 0.500 -— 0 —--- ----- ----- 0 6800 1.5 1243 0.511 -— 0 —--- ----- ----- 0 7100 1.5 1044 0.500 -— 0 —--- ----- ----- 0 7540 1 1471 0.500 -— 0 —--- ----- ----- 0 7550 1 1152 0.501 --- ----- ----- ----- 0 7800 3.5 957 0.505 --- ----- -— 0 —--- 8250 3 952 0.575 --- ----- --- ----- 0 8904 5 1089 0.517 --- ----- ---— 0 —--- 0 10000 10 Fiss Fiss --- ----- ---- ----- 4 1800 500 0 1202 0.581 168 0.880 -— 0 —1500 1 1165 0.426 215 0.881 0.5 1.480 0 5000 1 1521 0.454 298 0.895 6.2 1.611 0 5500 1.0 1556 0.449 295 0.989 28.5 2.005 0 5650 0.5 1295 0.408 256 0.890 4.0 1.480 0 5800 0 1564 0.423 289 0.880 ----- ----- 0 5800 3.5 1258 0.593 429 1.145 142.7 1.677 0 5800 1 1580 0.422 276 0.907 10.6 1.584 0 5850 3 93355 0.55 246 1.191 59.5 2.169 0 5900 2.5 1117 0.469 309. 1.005 38.4 1.892 0 5950 3.5 1258 0.595 311 1.166 61.1 2.556 0 4020 5 1169 0.408 174 1.024 20.0 2.141 0 4180 5.5 Rupt ---- -- ----- ----- ----- 4

l l - * — Fig. 1. Slight fissuring in ma- Fig. 2. Slight fissuring in matrix, Chromel ASM alloy, 2000F, trix, Chromel ASM alloy, 1900~F, 100 hr, stress 750 si, 50x,100 hr stress 1120 psi, 50x, cross section, unetched. cross section, unetched. A C,.T 5 4'. Pt Fig. 3. Slight fissuring in ma- Fig. 4. Fissuring in matrix, Chrotrix, Chromel ASM alloy, 1900~F, met ASM alloy, 1900~F, 100 hr, 100 hr, stress 1080 psi, 50x,stress 1125 psi, 50x, cross seccross section, unetched. tion, unetched. WADC TR 55-470 Pt 2 14

* /.*........,-'' I -c -J 11 41 v. ~,....'~'"-''.r::,.," 4'.-..'"",,' - 4'^' * *-'"'".-;I. cross section; u ntched. c ross section, unetched. - WADC TR 5-70 P 2*....' JN4.,Fig...Fissuring throughout ma-Fig. 8. Fissuring throughout matrix, Chromel ARM alloy,.e.,,,,Chromel ARM alloy, heat A,.ADC.T. -5-, 0.-. 2... F~~g. 7. /- F4sYrn truot m- Fg.Fsu~[truhu ~: I'i ~~a b~~e f4 tiC hrmlAMaly et~ Ai tix Cromel ARM~~ alohetA 180~F 100= hr'stcres 00 pi, 00F0r s trs100p, 50x, c~~~ros etouece. 5xcosscin nthd WADC TR 55-470 Pt 2 15)

H 90 8080 ISo 0 c+ 70 140 /00060 120 _c 7 E _ 0\ z yz 4 0 /C t ~~~~~/ 3/ Pd 430 / 80 /e~~~~~~~~~~~~~C ^ z //5 / /'/ 30 2 w w i80011900rF 7 e201o 20 -' —-- - 40 0 1000 2000 3000 4000 5000 6000 0 1000 2000 3000 4000 5000 6000 TIME-MIN TIME- MIN Fig. 9. Application of parabolic relationship Fig. 10. Application of parabolic relationship to weight-gain data; Chromel ASM alloy, to weight-gain data; type 510 alloy, heat 25159.

g IC00 450 --- ~sd \J1 W C 60 ----------— _-400 0 C+ 1400 350C ------- R)O 2000"F 1800F 1200 -30 _ — — 3_00 -- CY CY CY c OGO --- - ---— 250 E 8000. 20C o 9002 - - - - - - 200 I I S600 ------— 150 --- CY / ^/ i / I I 400 -40,0 100 --- -I~~o~F E I I I E19000 F z 200 -— 0 -— 50 -- ^ J40^F^_^_^-1400OF 0 1000 2000 3000 4000 5000 6000 0 1000 2000 3000 4000 5000 6000 TIME-MINTIME - MIN Fig. 11. Application of parabolic relationship Fig. 12. Application of parabolic relationship to weight-gain data; Hastelloy B, heat B-1400. to weight-gain data; type 510 alloy, heat 4X-545.

0 -900 900 800- - 800 0F 700 700 h co 500- - 500- - U. UJ w w " 400 - 00 n-1 11 210 -' 1560psi > I21'50 psI tm = 300 - 300- z z 1535 a 1 IO550psi 2200ps1 200- *- -- -- -- - 200 960psi I 1150plI \ 1520psi i00m~~~~~~~~~~~~~~ l125 10 00 \i —-10 - ^NO STRESS NO STRES ^\OOOp~s~ I I s _ _ __:1500pl_ 0 0.001 0.002 0.003 0.004 0.005 0.006 0 0.001 0.002 0.003 0.004 0.005 0.006 DEPTH OF PENETRATION, INCHES DEPTH OF PENETRATION, INCHES Fig. 13. Penetration vs depth below surface. Fig. 14. Penetration vs depth below surface. Chromel ASM alloy. 17000F, 100 hours. Chromel ASM alloy. 18000F, 100 hours.

0 r-3 900 900 ---- 6 800 800 clI~ 700 --- - - - - - - — 700 600 -- - -------------— 600 I I o o z z IU II.I a. 500 500 500 HM~~~~~~~~~~~~~~ ^<o ~~~650P51 I W " 400 - 400 L. L. 0 0 NO.a.. STRESS w w: 300- - 300 z z 200 NO 50200 60 Opsi —\ IlOOp$1-!O-..s\s \ 60 Opsi loo0psi~\ - \ 11060psi50ps 100 ps100 400pi 4 1105 psi *075pi\ 1/ 20psi NO _ ^:^ ^^ ____ _______ _ ______STRESS- - 650psi' ___ 0 0.001 0.002 0.003 0.004 0.005 0.006 0 0.001 0.002 0.003 0.004 0.005 0.006 DEPTH OF PENETRATION, INCHES DEPTH OF PENETRATION, INCHES Fig. 15. Penetration vs depth below surface. Fig. 16. Penetration vs depth below surface. Chromel ASM alloy. 19000F, 100 hours. Chromel ASM alloy. 20000F, 100 hours.

4800 60 4000 50 C, w o 0 c 3200 40 C w STRESS,,~ PSI ~~z C. z w 3 40 ---- -500 1000 1500 2000 20 STRESS,3PSI Chrome ASM alloy. 00F 100 hours. 55on-2 800 ---------- ation IO 500 1000 1500 2000 2500 STRESS,PSI Fig. 17. Summary penetration-frequency curves. Chromel ASM alloy. 1700~F, 100 hours. U) I w I z Z.0 40 N0 i z a0. z 0 30 w I10 celongation 500 1000 1500 2000 2500 STRESS, PSI Fig. 18. Summary penetration-depth curves. Chromel ASM alloy. 1700~F, 100 hours. WADC TR 55-470 Pt 2 20

:::cNUMBER OF FISSURES PER INCH ~>- roN (J 0 C-D MEAN PENETRATION DEPTH, INCHES X 103 m.0 0 0 o - o o o o o g I'^.. ~ u}""'\~" -— ~~~~~~~~~~~~. \J1\ o- 0ct 0 00 Frj ~ ~ ~ ~ ~ ~ ~ ~~c ~.oH -^~~~~~~~~~~~~~H? oa?. i..^- 8~~~~~~~I_______ ___ ________ ____ OI - o'}O'q ~ ~~0 o o oD,. 0 (D I oHc Hc~ I~~~~~~~~~~~~~~~~~~~~~~c H I u I Oct CO C.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~O OP~~~~~~~~~~~~ co I 0H*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~- 0 * 0~~~ 0S a Inl s H' 0 /~~~~~~~-0 o 0o 2 - _ _. r i H —on. o~ ^\ ___, ___ _____ __, __c~ _ ___ c - l- o,,v^ ^> irJ 0 I --- O' 0 c+ _ N? I \I 0 s 0 _ _ _ o. C~~ihi 0 I> 0 CD 0C 0 CD (D C (1)~~~~~~~~~~~Co) N F - - (D~~~' C'...... c;, g'" - 0 0 - - - - F-J ~ ~~... co o1 o oCo+ 0 P) 0 F0 0 0 o o o o o o PERCENTAGE ELONGATION IN 2 INCHES (A) PERCENTAGE ELONGATION IN 2 INCHES f i —-,- ----- I. — _NUMBER P. C." Li 0 ING ~~~~~~~~~~~~~~~~~~~~~~~~~o o o t NUMBERF FI S S U R E S P E R I N C H EXCDI N G M I N O R G R O U P + C+ 0~~~~~~~~~~~~~~~~~UBRO ISAE E NH ECUIN IO RU 4

4800 60 1200 + 0. 0 4000 50 — 1000 S w o W: 3200 N - 800 O 0 z o.+ z 5z 2 /v>~~~~~~~~~~~~~~ z o wnumber D3~0 1000 10 2 00 (n 2400 30.600.loy ation o CD r I excluding A; w |) 800 l I I 200 -'oE~ ~ excluding Ist, 8 2nd 20 a _ 10 500 I000 1500 2000 2500 STRESS,PSI Fig. 21. Summary penetration-frequency curves. Chromel ASM alloy. 1900~F, 100 hours. 1.5' so60 to -------- 50 0 Cl x w C I w excluding C o ffirst group Z Z 1.o ______ 40 c = &, + z a. z w 0 0 - 30 a z w Y o. ~' —------------ -f --- - --- --- ---- 0 -_depth ~ -ud CLo / Z J a. ____ ___ ~10 ia^ iAlohotion 500 1000 1500 2000 2500 STRESS, PSI Fig. 22. Summary penetration-depth curves. Chromel ASM alloy. 1900~F, 100 hours. WADC TR 55-470 Pt 2 22

4800 60 -1200 4000 50 -I 1000 C) w 0 / I i aC 3200 --------- / -------------------— 40 - 800z C a. z ~ I excluding first -J w. 0 w,' 2400 30 - 00 cu Tz 0 0 a:: a. 160C 20 AS 400 W Az U rCD ^ 0 w W 2,^^< K o -5'03 z +_ U. 8 10 00 -200 excluding Ist and 0 2nd group Cbgoti.on w 500 1000 1500 2000 2500' z STRESS, PSI Fig. 23. Summary penetration-frequency curves. Chromel ASM alloy. 2000~F, 100 hours. 1.5 60 0 I 50 X 1 sexcluding first grobjp U w w 0 z 1.0 40 N ~I r i I I 1 I+ z w 0 0 z0~~~~~~~~~~ z 0 00 I w ______ _ ___0 z 0.5 20 0 w z depth C -— a —-.- - -- ------ ------ a, Io/^ego.iongo 500 1000 1500 2000 2500 STRESS, PSI Fig. 24. Summary penetration-depth curves. Chromel ASM alloy. 2000~F, 100 hours. WADC TR 55-470 Pt 2 253

:: m,- -_ _ 900 - --— 2500psi | — 1000 a 1300psi \J1 I' i 2Opnsi - -- 2350psi 800 800 -975psi_ 1065psi -2000psi n5d c+ -2420 a 2245psi 1500psi ru 700^ 700 ) 7 -g — 2710 a 2550psi 1580 a 1550psi 600 -- I _ - - _ -— 600 5 [j~~~~u 1690psi z z. 500 aj 500 500 I " ) iC i) uL 400 i!:400 LL l:- i 40 0 i I~ o o wiiiw D 300.- 300 i -- — 0 75Opsi 2000psi 200 200'IM\~~~~~~~~~~~~~~~~~ \ ^^MR 1500,1550 a 1580psi 2610psi,-2385psi I 65a 13-00-psi 100 100 /I 65oo \ ^ \N-.P' I I I'^^ l69^SOpsi 1395ps i 0 0.001 0.002 0.003 0.004 0.005 0.006 0 0.001 0.002 0.003 0.004 0.005 0.006 DEPTH OF PENETRATION, INCHES DEPTH OF PENETRATION, INCHES Fig. 25. Penetration vs depth below surface. Fig. 26. Penetration vs depth below surface. Type 310 stainless, heat 25139. 1700~F, 100 hours. Type 310 stainless, heat 25139. 1800~F, 100 hours.

9002pi 900900.. I [ i-650psi J1^ Ii r 775 & plOpi tS- a oo- 500psi - 900psi 800 800 00 -J 800 — i t^ - 900Psi ---------— _-______________ -^ I I ~KT lOlOpsi 300psi Fd i 1/ - 570psi c-F \~!'C7 2000psi 0 700'- 700-2000psi~ — 620 a 755psi 700.700I hI/f, 620psi 600 - 600 o I o ir z iia;t Z a. 500 ai —---- 500 w \,cnp (/ (/3 I o W U- iU1 - 300 - 300 z zw 130 0 I _ _ _ _I_ _3 775psi 00 200 a 3 5psi 100 l\ IOpsi O/1050psi 0 0.001 0.002 0.003 0.004 0.005 0.006 0 0.001 0.002 0.003 0.004 0.005 0.006 DEPTH OF PENETRATION, INCHES DEPTH OF PENETRATION, INCHES Fig. 27. Penetration vs depth below surface. Fig. 28. Penetration vs depth below surface. Type 310 stainless, heat 25139. 19000F, 100 hours. Type 310 stainless, heat 25139. 2000~F, 100 hours.

2400 1 -1200 I a. w 0 r 1600 40 N - 00Z twj | t | j excluding fir t grfC, | z 5 -J \. z 00 W 12 001800. 2400 230 4 00 wa~~~~~~~~ z~ (z 80.. 2. 1 400 A 6,z. (elongation:/I/ 400 aoo060 ------.t l | excl ding group+ bJ 61 00 2400 3000 z STRESSPSI Fig. 29. Summary penetration-frequency curves. Type 310 alloy, heat 25139. 1700~F, 100 hours..5 560 r. 150 u LU (O excluding first group/: -- z -- +' 400 =?~~~~~~4 z I- -.. —.. —-- -- -' - a. Z w 0........ T 55-470 2 2630 ~~~~0~~~~~~~~~~~~~0 LuouU I z depth STRESS, PSI

02400 60 -1200 I, 2000 50 - -1000 o zn z number o I I | < [ | |A ZI Ca 1600 - - \ /40 800 excluding first group A Z = 1200 r / t elongotion 0 0 0 z x D 0L 1 1 2000 200 0 Fig. 31. Summary penetratdion-frequency curve s w z Type 310 alloy, heat 25139. l800~F, 100 hours. w 0 400 2. - O O 0 A cA IIA I' z 500 1000 1500 2000 2500 STRESS, PSI Fig. 31. Summary penetration-frequency curves. Type 310 alloy, heat 25139. 1800~F, 100 hours. 3.0WC TR 55-4760 1_.5 3....50 o 0 I w Iw 0 z 2.0 40 c +-r1 z w w 1.51 r -- - - r 30 C3C~~~~~~~~~~C excluding first group elongation c W1.0 T 20 a. 4 T - z 0.5 10 500 I 000 1500 2000 2500 STRESS, PSI WAD~C TR 55-470 Pt 2 2 7

2400 60 1200'< u) a. 2000 - -. 5 I00 00 w a. z zc o 0 n0 w 1200 3 0 C 40 w z..o o'.:T, P S W __^/__. C — 4 00 0 400u" I2 I O e pt ewl~ifexcluding t grs C) a. 400, r 0 200 I 1 1 / eloiexcuding Ist Z C and 2d groups!1 500 1000 1500 2000 2500 z STRESS,PSI Fig. 33. Summary penetration-frequency curves. Type 310 alloy, heat 25139. 1900~F, 100 hours. 1.5WD "....T 55460 rr)z~ ------ 4 ------— ~~~~50 4 W /) - Hi f excluding first group o w1. —--------------------- -Cz - Z w 0 Z A r z a.,, --— ^"^ y e tRESSon P Fig.. Sumayentrtin-epS w 500 1000 1500 2000 2500 WADC T 55-4702STRESSPSI Fi/.Iynerationn Type 310 alloy, heat 25139. 1900~F, 100 hours. WADC TR 55-470 Pt 2 28

2400 60 1200' —- — ^ ^^ 4 0 2000 50 t000O z z z G 1600 -40 -800 n' z Z v - - exduding 3, M- f irst group) g un 1200 30' 600 W co) z UJ 0 U- W 0o0 800 120 2 400 A _/ elongatlonw o | =- --- ----- x - = a^<^ - exduding Ist STRESS, PSI z Fig. 35. Summary penetration-frequency curves. Type 310 alloy, heat 25139. 2000~F, 100 hours. W z z w i ci r(~~~~~~~~~~~~0~ ~ ~( I XI I I 1 Z 1 Ld j 1.~0~ - ---------— r__ -,^ —----- |excluding xlt 0 200 J400 600 800 100 STRESS,PSI Z Fig. 35. Summary penetration-frequency curves. Type 310 alloy, heat 25139. 2000~F, 100 hours. 1.5 60 0 x w I (r II z ~~Zj_ 1~~~~~..... 11, 40 cN! I I I texcluding z 300 (9 z z o 0 4F depth vW zW 05 0 0 _ (.9 W. 20 Iz Z (L: < w 10 A Z~ elongation 200 400 600 800 I 000 STRESS, PSI Fig. 36. Summary penetration-depth curves. Type 310 alloy, heat 25139. 2000~F, 100 hours. WADC TR 55-470 Pt 2 29

C: 900 - - I 9 - mm-900 I 9 0 0 I".-15700psi \J1 I\I 15000 50i Ln^j I_ -- -- 5 PI - 5140 8 19100ps 800 — - 800 o~J!i~ 49!o, 1Id 10250 psi 10' 17770psi Rb 700 I {70'0 I! 7 16900 i I.' I iff —-t 7775psi I 1:1 I ~ — I~~~~~~~~~~~~1000, 8900, 11 —- 19250 psi, 10000, 11800 600 T~~~~~~~ 60C - B~~~~~~& 16900psi 600 600 i --- 7470 a 8650psi z l cI M. I ~ 4~1~ —-+ —- 2050 psi a. 500. 500 O; 400Q Q 1 _, 0 w, 1 300 300 i 3 300'1 200 -- 200 - -- -- i, /19K)Opsi 100 100 i 17770psi 0 0.001 0.002 0.003 0.004 0.005 0.0060 0001 0002 0003 0004 0005 0006 DEPTH OFDEPTH OF PENETRATIONEPTH OF PENETRA INCHES Fig. 37. Penetration vs depth below surface. Fig. 38. Penetration vs depth below surface. Hastelloy B, heat B-1400. 12000F, 100 hours. Hastelloy B, heat B-1400. 14000F, 100 hours.

900 E9aoo,!_ _____ Psi 9 o 3900psi ^ ____ S740a 7530psi | — -1500 a 3950 psi - 7340 a 7530psi'- 800' ---- 8 -- - 3500 a:800psi 0 o r- ~ 3000 a 3800psi ^^t -500SOOpsi ro 7800psi 700 -+ —3850psi 600 ~.r 3000 8 \6 -o IO rOOpsi I _z i z a. 500 3,00 — I' 1 no ~ - 7800psii 40 400 -\ 200 =XI ^:5_3800 p_0_.......\\..95si 0 0.001 0.002 0.003 0.004 0.005 0.006 0 0001 0.002 0.003 0.004 0.005 0.006 DEPTH OF PENETRATION, INCHES DEPTH OF PENETRATION,INCHES Fig. 59. Penetration vs depth below surface. Fig. 40. Penetration vs depth below surface. Hastelloy B, heat B-1400. i600~F, 100 hours. Hastelloy B, heat B-1400. 1800~F, 100 hours. Hastelloy B., heat B-1400. 1600~F., 100 hours. Hastelloy B. heat B-1400. 1800~F, 10 ours

2400 60 2000 - 50 () w I | I z z z 1600 40 c J a. z w 0 1200 -30 U,.. n*umber..-n"'u "S 0 a 8008000 1 1 20 0 z w.....Z~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~2~0 A,,, A - I A 4000 8000 12000 16000 20000 STRESS,PSI Fig. 41. Summary penetration-frequency curves. Hastelloy B, heat B-1400. 1200~F, 100 hours. 1.5 60 tE) 5o 0 w C I L I | d z | |] z z 1.0 40 c. I- z,. Z w 0 Q 30 CD R -2 I- LwU l CD z o0.5 _______.... 20 dtdepth z z ~ 4 ------ w A'. I0 4000 8000 12000 16000 20000 STRESS, PSI Fig. 42. Summary penetration-depth curves. Hastelloy B, heat B-1400. 1200~F, 100 hours. WADC TR 55-470 Pt 2 52

2400 60 2000 50 V) ~~I~~~~~~ ~~~~~~w z z cr 1600 40 CJ4 w o n 1200-30' number ii- $0 * *. 0 0 * a: 800 20 w z M I I 1 0W 400 10 elon tiono __ A 4000 8000 12000 16000 20000 STRESS, PSI Fig. 43. Summary penetration-frequency curves. Hastelloy B, heat B-1400. 1400~F, 100 hours. ~~~~~~~~~~x ~~~~~ ~wa.''0 40 0 x" z I LJ a. Z W 0 1.0...... 430 a. z z z t a:: 4I _ _ _ _ _ I W aa. 10,,,,,. AA,, A A 0.......~ ~ A Fig. )-I-. Summary penetration-depth curves. WADC TR 55-470 Pt 2 3

2400.60 C) Iw C) I: 1600 - 40 CN w 00 z co z G 1200 30 h_ number 0 LL. OI. I.z. c- 800' 20 w z ~ w 400 10 WwongOtion __ 2000 4000 6000 8000 10000 STRESS, PSI Fig. 45. Summary penetration-frequency curves. Hastelloy B, heat B-1400. 1600~F, 100 hours. 1.5'''' J" 60 x wC 1 _' " 150 I z Co I z I-' a. z w STR 00 F ig. 46. Summary penetrat ion-depth curveiso. Hastelloy B heat B-1400. 600~F 100 hours. STRESS, PSI WAPO TR 55-470 Pt 2 ~

2400 0 60 600 0 n2000 50 500O w Cr I || I 0 o 0 z C.) z ~~~z ~~ ~~~~~+z - c 1600 40 4 -400LO. z c <nS~~~~~~~.number z w 02 X MC w v0 Z O ~ ~ __ \ ____excluding firsLgroup W a 80 1200 2 — 2 3'200,00 z a40Hastelloy B heat B- 1000 100 hours. 0 - D 2000 3000 4000 5000 STRESS,PSI Fig. 47. Summary penetration-frequency curves. I | excluding ist ttnd 2 Lroup I " I ^ I relog b 1 *> I 2.5 50 0 I excluding fst and 2nd U Z a. 1 1.5 30 O a5z, > I ^ z^^>srISTRESS,',PSI - f Hastelloy B, heat B-1400. 80excludi0~ frst group rs. W ( 55 Z 1.0 20 _ z w 0.5 10 elangalin 1000 2000 3000 4000 5000 STRESS, PSI () fractured during test Hastelloy B, heat B-1Z00. 18000F, 100 hours. WADC TR 55-X70 Pt 2 5

-- 900 900 in 900 - 300psi 900 ---- 500 650psi "l r -- 953 psi 750,720, 454, \J1 6 00pu1400 a 300psi 800 800 Ia670 a 400psi 900 a 850psi 700 - -- - -700 - 600 600 1 - - — 6001 ~~~~~I Iii, ~~~~~~~I~ o II. | 0 z ~~~~~~~~~~~~~~z ~ 500 — ^ -- -- ---- -- ---- --- --- - --- -- -'- -— ~ 500 ---- J - -- - - --------------------------- 8 i'wII 00 00 w w 953670 L 400 u-\I^^Y^"' 40089 a 600P74 0 0.001 0002 0.003 0.004 0.005 0.0060 0.00 0.002 0.003 0.004 0.005 0.00 (n ( DEPTH OF PENETRATION, INCHESDEPTH OF PENETRATION,INCHES Fig.00 0. Penetration vs depth below surface. 953Type 510 alloy, heat 4X00F 100 hours. Type 510 alloy heat X-55. 2000F 100 hours. 750 702:00 psi a E i689 & 600ps Type 310 alloy, heat 48-343. 19000F. 100 hours. Type 310 alloy, heat 4X-343. 20000F, 100 z

2400 - 240 x 2000 50 200 w I0 z z jM 1600 -140 c' -160 z 0L ~ Fg. 5 Su_ - 0.. e-60 2A f number z co+ ~z uw u) 1200 3 0 -20 U) ex.uding ls I U. o w _ 8so 20 4 800 00 111 z STRESSPSI m z 5. Summary pe 400 10 40 200 400 600 800 000 STRESS, PSI Fig. 51. Summary penetration-frequency curves. Type 310 alloy, heat 4X-343. 19000F, 100 hours. 0.61 so 0 0 x -.5 5 0.5 - 50 -2.0 z X.......... 50,j excluding Ist 3 I z 5 &_8/ 2nd sous. z z 0.4 40 cm - 1.6 ~~~~~~~~0.4~~~~~ z = = = z z ~4 excludXng 1st group ^ 3 0 z <lj X excluding Ist w w I- wz 0.2 LI....20 -O O 8 a. z "' w oC z A 4 w Z I 00.. 2 10 elongation 200 400 600 800 K)OO w STRESS, PSI 8 Fig. 52. Summary penetration-depth curves. Type 510 alloy, heat 4X-543. 1900~F, 100 hours. WADC TR 55-470 Pt 2 57

2400 60 -240 excluding Ist group 2000.50 -200 Ol~~~~~~~~~~~I OI^^~~~~~~~~~ -- O: G.j.10 0+ uo z =o~ -,2o 0 O, | l | t | / | elongation w n 80C-/- 20, -80 a: w 10 40 5 4 800 1 0 0 80 w, z w STRESS,PSI Z Fig. 53. Summary penetration-frequency curves. Type 310 alloy, heat 4X-343. 2000~F, 100 hours. ~v,~~~~~ ~x o 5. S p t o r N c T w 1,, L O r 0.15 5 - -- - 50 -2.0 xephI z e z Type 310 alloy, he at 4X - 343. 2000~ F. 100 hours. W TR 55 —-- P 21 3 ~ o3excluding tot grgup ~ Fig. 53...... g....y pn -re 01 ~ u~1 I-X w z 0., 100hors w o 5a 02 i0 z 0 w 1' 200 400 600 800 1000 STRESS, PSI Fig. 5)4. Summary penetration-depth curves. WADC TR 55-470 Pt 2 3 8

- -;-'.', "'^ "-', -- "'''~ ~', Jw,, -, i.. F ig...Chromel alloy ASM:, as Fig. 56. Type 310 alloy, heat.-.^s?'.i'.. ig.. el alloy, a Fig.. Type 310 alloy, heat ~- - 7,r ed. 50x; ross section., -1 39. As received. * 100x;' "-;<-*.7 K;',.; -',- f,r' a^^:' = v.'.,;1 i'; ^.^':' i "- -'-\^ < T^X ^; ".;*; - > D- / *.,'.:"::'.'""..":* -- -' *. "-.\'.'".'." "' *.-. -' -.','. t'.: F-. 5. Chromel aloy _~ A',,'ag. 5_. T)pe 510 " l. >"'', acid5 H.C lyial sin chromic acid.-, _ -.-,.'",-.:',.Z: ^ ~ r,,:-';.' —'.',< N.. /AL, /X"..',, Fig. 5 h... rm.. el.. alloy.M, -. Fig,.-. Type.10 alloy, heat r-1cv-e,. 50x; cross section, 5:9. As received. lOOx;,,c rs, 1-1'.'-.5. Hyl H':, H0'c..hm.-iha-.-'.WADC ~.. J.,7 R,-4......-..-0 Fig. 57. Haste..oy B alloy, heatFig. 8. Type 510 alloy, heat, B-1400. 50x; cross section, 4X-513. As received. lOOx; ~ etched electrolytically in chroiccross section, etched electro11 Nacid. 0 H lyticallys in chromic acid. WADC~~..: h~r TR 55r-47 Pti 2

,~ ),.'. t',V:.." r,'- ^^- r ^ ^^^ ^ -— 1. — * - ~' -:,-*:.-.- - -.. _.'..'.,,..,p*..-': _. "'"' r r N /.X''.'A'k.'\'.;" —. 4""-.,": i:/-'"'''' Fig 59. Type 10 alloy, heat 251. Fig. 60. Type 510 alloy, heat 25159. 17000F, 100 hours, stress 2245 psi. l800~F, 100 hours, stress 1580 psi. lOOx; cross section, etched elec- lOOx; cross section, etched electrolytically in oxalic acid. trolytically in oxalic acid. \ ~ 1,.-'. vL.- * -yo.., <'.-.. -. /. 19000F, 100 hours, stress 755 psi. 20000F, 100 hours, stress 755 Psi. -x; cross section, etched elec~~ - x; cross section- etched elec- ^,<A. ~.';C- I -':..' /'., ~..-.-:(...',.'~ i.''t...."':,,. \ ~ -..' "'^ -...",, *'T Fig. 6.'Type 10 alloy, heat 251"9. Fig. 62. Type 510 alloy, heat 2519. 1900~P, 100 hours, stress 75 psi. 2000F, 100 hours, stress 755 psi.,,-.x; cross section, etched elec-lO0x; cross section, etched elec. trolytically in oxalic acid. trolytically in oxalic acid. WADC TR.~55-470 Pt 2 40CC 190"F 10 ou..'tes;. pi,:00,~:0 "?~'.',. st.s.... 100xc~~~~~~~soss~~~ I'_'%ethdeec 0x cossctoechdee:-:,-.,:.,.,..,.. i... ).:.~.~:.::.~,. trl.~cl..',~;-,,. -:., WADC TR 55~~~~~~~~~~~~~~~~~~~~~~~~,-47...,~

',... *'.' " Fig. 63. Hastelloy B, heat B-1400. Fig. 64. Hastelloy B, heat B-1400. 1200~F, 100 hours, stress 19,250 1400~F, 100 hours, stress 10,000 psi. lOOx; cross section, etched psi. 75x; cross section, etched electrolytically in chromic acid. electrolytically in chromic acid..-,. — ___ -. -* I *k.... ~.... Fig. 65. Hastelloy B. heat B-1400. Fig. 66. Hastelloy B, heat B-1400. or,psi. lOx; cross section, etched psi. lOOx; cross section, etched electrolytically in chromic acid. electrolytically in chromic acid. WADC TR 55-470 Pt 2 41

-*"'> D,\- <~~L' _' / i ^' ^'" - -''.. V'9V~ ~~~ >- - * -:. -"~':'~,^ >....:''......~:i......"'*r'"......-' *'"'"' -'." *', (^*:' "'.'" ~ ~:' - I.. -& r "'::'>.''.' " r'.....-' " L'. ", -..2; 4X-34. 1900~F, 100 hours, stress 4X-343. 2000~F, 100 hours, stress 750 psi. lOOx; cross section, 600 psi. lOOx; cross section, etched electrolytically in etched electrolytically in chromic acid. oxalic acid. I-":/:''.~. &'-,;', Fig. 69. Chromel ASM alloy, 2000~F, Fig. 70. Type 510 alloy, heat 25159. 100 hours, stress 750 psi. 250x; 19000F, 100 hours, stress 1096 psi. dross section, etched electro- 100Ox; cross section, unetched. lytically in 1-1-5 HC1, HNO, H20 solution. WADC TR 55-470 Pt 2 42

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