TENTH PROGRESS REPORT TO MATERIALS LABORATORY, WRIGHT AIR DEVELOPMENT CENTER DEPARTMENT OF THE AIR FORCE ON FOUR LOW-ALLOY STEELS FOR ROTOR DISKS OF GAS TURBINES IN JET ENGINES by R. L. Jones A. I, Rush J. W. Freeman PROJECT M903 AIR FORCE CONTRACT NUMBER: AF33(038)-13496 SUPPLEMENTAL AGREEMENT NUMBER: S4(53-534) EXPENDITURE ORDER NUMBERS: 605-227 SR-7 and R615-13 SR-3a June 30 1953

SUMMARY The original investigation began as a study of the high temperature properties of four. low-alloy steels: 4340, "17-22A"S, H-40 and C-42Z, in the form of forged J-33 jet engine disks. A concurrent investigation of the high temperature properties of the products of isothermal transform mation of each steel was carried out utilizing bar stock. The investigation was then extended to include a more complete investigation of the products of isothermal transformation, as well as the normalized and oil quenched structures. The original investigation of the jet engine disks and the concurrent study of the products of isothermal transformation have been completed and reports are now being prepared, This progress report covers the period between April 1, 1953 and June 30, 1953, Survey type testing has been started and data obtained at 700~, 900~, 1100~ and 1200~F for the. "17,ZA"'S steel. Data has been accumulated at 700~, 900., 1000~ and 1100~F for the 4340 steel. Tests are now in progress at 700~, 900~, 1100~ and 1200~F for the H-40 steely but no additional data have been obtained during this peried. The data have been organized to include data previously obtained, as well as those from current tests at the new temperature and on the new structures, The tests conducted to date are not conclusive. The trends being obtained, however, are interesting and are as follows: 4340 Steel At 700~F and a stress of 90,000 psi the normalized structure had the best strength, whereas at 900~F and a stress of 55,000 psi, the lower bainitic structure had the best properties. At 1000~F and 13, 000

2 psi, the upper bainitic structure is the strongest, but at 1100~F and 4,500 psi there was little difference between the upper and middle bainitic structures, both being somewhat stronger than the next strongest, the norm. alized structure. "17-22A'"S Steel At 700~F and 115,000 psi the oil-quenched structure was stronge.st, However, the stress was too high for a good evaluation, At 900~F and 70, 000 psi:, the normalized structure appears to be slightly stronger, but the bainitic structures had good ductility, At 1100~F and 19,000 psi the lower bainitic structure had the best strengths but at.1200F and 7, 500 psi the middle pearlitic structure appears to be strongest. H-40 Steel No additional data have been accumulated for the H-40 steel during this period.

3 INTRODUCTION The Materials Laboratory, Wright Air Development Center, is sponsoring an investigation of the high temperature properties of low alloy steels for use as forged wheels for the gas turbines of jet engines. This progress report covers the period between April 1, 1953 and June 30, 1953. The work is being carried out under Contract Number: AF 33(038).13496 (Expenditure Order Number 605-227 SR-7) and Supplemental Agreement Number: S4 (53-534) (Expenditure Order Number: R615_13 SR i3a). A final report presenting the properties of forged wheels of 4340, "17-22A"S, H40 and C-422 alloys is in the process of reproduction. It will be submitted early in the next period. For purposes of simplicity and usefulness, it has been decided to submit two final reports, A second report is being prepared to present the original results from studies of the products of isothermal transformation, as related to the properties at high temperatures. In addition. this report-will present an analysis of the microstructures of the wheels and attempt a correlation, as far as possible, of the structure studies of the bar structures This present progress report also presents the results of considerable progress on the survey tests of the current program.

4 RESULTS During the period covered by this report, the work was nearly completed on a final report presenting the properties obtained in the investigation of forged turbine wheels. The correlation work in structures of the wheels and bar stock studies is continuing and is nearly ready for reporting, Structures to Be Investigated The structures and treatments to be investigated are outlined in Tables I through III. Certain idealized structures were selected to cover the range of structures possible from the transformation diagrams, These idealized structures -have been given simple names in order to provide a convenient means of referring to the treatments and structures in the text, It is important to realize, as is outlined in the tables, that the actual structures deviated from the idealized structures in some cases, It should also be realized, for example, that the "upper pearlite" of the 4340 steel is a different structure from the "upper pearlite" of the " 17 -22A"S steel, and in turn these two structures are different from the "pearlite" formed in the H-40 steel. A nmore complete discussion of the nomenclature used will be found in Progress Report Number 9. Heat Treatment Studies The data obtained from the survey tests for the isothermally transformed structures and the oil quenched and normalized structures are given in Tables IV and V. These tables have been organized to in

5 elude data previously obtained, as well as those from current tests so as to. completely present available data, The following general trends regarding relations between structures and properties at high.temperatures appear to be shown by the data obtained to date: 4340 Steel 1, The test data are.still considered too limited for definite conclusions regarding the relationships between structure and strength. 2. At 700 ~F, the normalized structure (65% bainites + 35% martensite) had the best strength of the structures.tested on the basis of the time to reach one-per cent deformation or mi iun creep rate under a stress of 90,000 psi, The "lower bainitic" structure (100% lower bainite) was next strongest. There are two major limitations to the available data. None of the "pearlitic" structures have yet been tested, Secondly, only one stress has been used to date, The stress of 90, 000 psi is somewhat above the proportional limit, of the specimens thus far tested. 3. At 900~F a stress of 55, 000 psi was used. It resulted in fracture of all the specimens tested in time periods ranging from 4 5 hours to 1417 hours, "Middle" bainite (100% medium acicular bainite) had the longest time for fracture and the lowest minimum creep rate. There was a considerable decrease in strength to the next two strongest structures, "lower" bainite and normalized material, "Upper" and "lower" pearlite were both very weak comparatively. The stress level was such that the time to reach one-per cent deformation was rather short and largely controlled by the initial deformation. "Upper" bainite ought to be tested before too definite conclusions are drawn. Also at 9000F a lower stress throwing the comparison mainly on total deformation and creep rates ought. to be used for evaluation.

6 It will be noted that the "middle" bainite had rather low elongation and reduction of area, Even though the time for fracture was considerably longer than for the other tests (such values generally tend to decrease with.time for fracture), it appears quite certain that the medium acicular bainitic structure is associated with low ductility in the rupture test at 900~F for this alloy. 4, At 1000~F, "upper" bainite (70% upper bainite + 30% martensite) is the strogest on the basis of total deformation.and minimum creep rates. The normalized and "middle" bainite ranks next. It is interesting to note that "lower" pearlite was stronger than the oil quenched structure Rupture tests ought to be carried out on these structures before definite conclusions are reached regarding relative strengths of structures. "17.-22A"S Steel 1. The stress used at 700~F (115:, 000 psi) resulted in fracture of all the structures in rather short time periods. At this high stress the oil quenched material was strongest. These was very little difference in ductility for the different structures, all being quite high. It is considered that the stress used was too high for a good evaluation and tests should be made under a stress causing about one-per cent total deformation in 1000 hours for the stronger structures. 2. The stress used at 900~F (70,000 psi) also caused fracture of all but the normalized. structure, which appears to be the strongest structure at 900~F. The oil quenched structure appears to be slightly stronger than "upper bainite," but not as strong as "lower bainite," The bainitic structures had good ductility, 3, At 1100~F, all except the "lower bainite" specimen fractured in less than 1000 hours.* This specimen, however, was not as creep

7 resistant as the normalized specimen, even though it apparently had higher rupture strength. The spread in rupture times for the other structures was surprisingly small, Also, all of the structures had rather low elongation, except for "lower pearlite,:" The spread intimes for one-per cent total deformation and minimum creep rates was also rather small for all the structures, 4, At 1200~F "middle" pearlite has the best strength on the basis of rupture time, total deformation or minimum creep rate, As at 11004F, however, there was a surprisingly small range in relative strengths. Ductility to fracture was considerably higher at 1200~F than at 1100~F. H-40 Steel No additional data have been accumulated. The specimens have been heat treated and tests are now in progress. DISCUSSION The tests coiructed to date are not conclusive, The trends being obtained are, however, interesting and should prove useful, One finding which seems to be contrary to generally accepted concepts of the past is the comparatively low creep resistance of tempered martensite (oil quenched specimens) at temperatures as low as 700 ~F The data obtained during the next period, together with more opportunity to analyze the data should lead to more definite conclusions regarding the realtions between structures and properties at high temp. eratures,

Aim Structure Upper Pearlite Middle Pearlite Lower Pearlite Upper Bainite Middle Bainite Lower Bainite Normalized Oil Quenched TABLE I Type Structures, Heat Treatments and Actual Structures for 4340 Steel (All 4340 bar stock austenitized at 1750~F for 1 hour., ) Transformation Approximate Temp Conditions Structure BHN Temp- F Time.-hrs Obtained Temp-F F 1240 10 65% medium pearlite + 212/221 None 35% ferrite 1150 14 85% fine pearlite and fine 199/223 None carbide-ferrite aggregate + 15% ferrite 1050 111 90% very fine carbide-fer- 260/275 None rite aggregate+ 10% ferrite 850 28 o0% upper bainite + 30% 319/324 None martensite 750 24 100% medium acicular 302/313 None bainite 650 -1/.2 '100% lower bainite 430 1100 Air Cooled from 35% martensite + 65%o 385 1100 1750 bainite Oil Quenched from 100% martensite 585 1100 1750,ering Time-hrs -. 1 -1/4 1 10 BHN 212/221 199/223 260/275 319/324 302/313 277/301 300/311 304/309

Aim Struc Upper Pea Middle Pe Lower Pe; TABLE II Type Structures,'Heat Treatments and Actual Structures for 1 25 Cr-Mo-Si-V (l17-22A'"S) Steel (All " 17-22A"S bar stock austenitized at 1750 for 1 hour) Transformation Approximate Tempering ture Conditions Structure BHN Temp-F Time-hrs Obtained Temp-~F Time-hrso Lrlite 1300 1-1/2 45% medium pearlite + 309 None 55% ferrite arlite 1225 1-1/2 40% medium fine pearlite 26:7/285 None - 2 + 6.0% ferrite arlite 1150 10 40% fine pearlite + 60% 375 1200 12 2 ferrite nite 900 2 60%o upper bainite and aci- 465 1200 16 2 cular ferrite + 40% martensite Linite 800 1/2 100% fine acicular bainite 360 1200 4 3 inite 700 1/12 95% lower bainite + 5% 365 1200 12 2 ferrite sd Air Cooled from 15% martensite + 85% 355 1200 10 3 1750 coarse bainite hed Oil Quenched from 98% martensite + 2% fer- 525 1300 1 2 1750 rite Upper Bai BHN 309 67/285 93./.313 84/327 07/310 '73/30.2 302/313 '72/310 Middle Ba Lower Ba: Normalize Oil Quenc

Aim Structure TABLE III Type Structures, Heat Treatments and Actual Structures for 3 Cr-Mo-W-V (H-40) Steel (All H-40 bar stock austenitized at 1950~F for 1 hour.) Transformation Approximate Tempering Conditions Structure BHN Temp-~F Time-hrs Obtained Temp.~F Time-hrs 1300 24 fine carbide precipitate 190/199 None 750 10 40% bainite and acicular 480 1300 1 ferrite + 60% martensite Air Cooled from 30% martensite + 70% 435 1200 18 1950 bainite Oil. Quenched'. lfrr 98% martensite + 2% ferrite 523 1200 12 1950 Pearlite Bainite Normalized Oil Quenched BHN 190/190 293/312 312/320 290/323

TABLE IV Rupture, Total Deformation and Creep Data at 700-, 900', 1000~ and 1100F for 4340 Steel Temp- Stress Rupture Elong- Reduction Deformation Time to Reach Specified Total Deformations Minimum BHN erature Time ation of Area on Loading Creep Rate (F) (psi) (hours) % in 2" (%) (in /in.) 0. 1 0.2 0. 5% 1.0% (%/hour) Aim Structure Normalized 35% martensite + 65% bainites Oil Quenched 100% martensite Upper Bainite 70% upper bainite + 30% martensite Middle Bainite 100% medium acicular bainite Lower Bainite 100% lower bainite Normalized 35% matensite + 65% bainites Oil Quenched 100% martensite Upper Pearlite 65% medium pearlite + 35% ferrite Lower Pearlite 90% very fine carbideferrite aggregate + 10% ferrite Middle Bainite 100% medium acicular bainite Lower Bainite 100% lower bainite Normalized 35% martensite + 65% bainites Oil Quenched 100% martensite Upper Pearlite 65% medium pearlite + 35% ferrite Lower Pearlite 90% very fine carbideferrite aggregate + 10% ferrite 300 700 90,000 1294(d) - 0. 00516 304 700 324 700 309 700 277 700 300 900 306 900 217 900 260 900 313 900 277 900 301 1000 306 1000 219 1000 90,000 1350(d) 90,000 1316(d) 90,000 1315(d) 90,000 1485(d) 55,000 842 12.0 22.4 55,000 381 19.5 39.5 55,000 4.5 51.0 68. 8 55-,000 20 34. 5 37.9 55,000 1417 4. (c) 2.4 55,000 897 18.5(c) 15. 4 12,000 1000(d) -- 13,000 1025(d) -- 13,000 1103(d) - 0.00430 0. 00465 0. 00472 0. 00440 0. 00260 0. 00269 0. 00313 0.00380 0.00250 0. 00050 0.00060 0.00044 a a 2 a a 2 a a 1 a a 1 a a ^1 a a 8 a a 2 a a 0.13 a a 1 a a 8 12 114 802 3 27 248 6 63 528 0.000112 675 198 1291 2020(b) 64 13 0 000272 0.000320 0.000190 0.000160 0.00414 0.0148 3 1 0.55 51 0.00064 51 0.0053 2150(b) 0.00037 628 0.00115 1400(b) 0.00057 270 1000 13,000 848 21.4 24.8 0. 00062 2 6 46 141 0.00537

Temp Stress Rupture - Aim Structure BHN eratiure Time ation (:F). (psi) (hours) % in 2" Upper Bainite 322 1000 13,000 1075(d) 70% upper bainite + 30% martensite Middle Bainite 307 1000 12,470 1706(d) 100% medium acicular bainite Lower Bainite 294 1000 13,000 1035(d) 100% lower bainite Normalized 311 1100 4,000 1056(d) 35% martensite + 65% bainites Oil Quenched 309 1100 4,500 1080(d) 100% martensite Lower Pearlite 275 1100 4,250 1007(d) 90% very fine carbide-ferrite aggregate + 10% ferrite Upper Bainite 319 1100 4.500 990(d) 70% upper bainite + 30% martensite Middle Bainite 302 1100 4,500 1343(d) 100% medium acicular bainite Lower Bainite 301 1100 4,500 1008(d) 100% lower bainite (a) Specimen reached this deformation on loading. (b) Extrapolated value. (c) 0. 250-inch diameter specimen, elongation % in 1-inch. (d) Test discontinued at this time. ABLE IV, Continued Reduction Deformation Time to Reach Specified Total Deformations of Area on Loading. ) (in./in.) 0.1% 0.2% 0.5%. 0%. 0.00057 5 91 1130(b) - 0.00068 4 42 472 1920(b) 0.00055 2 32 300 1104(b) 0. 00017 18 96 484 1416(b) 0. 00027 5 22 104 258 0.00032 9 21 90 217 0. 00026 17 78 552 1585(b) 0. 00025 13 55 432 '1565(b) 0.00042 3 19 156 436 - Minimum Creep Rate (%/hour) 0. 00023 0. 00030 0.00053 0.00052 0.00316 0. 00390 0.00048 0.000445 0.00172

TABLE V Rupture. Total Deformation and Creep Data at 700', 900~, 1100. and 1200'F for 1.25 Cr-Mo-Si-V ("17-22A"S) Steel Temp- Stress Rupture Elong- Reduction Deformation Time to Reach Specified Total Deformations Minimum BHN erature Time ation of Area on Loading Creep Rate (~F) (psi) (hours) % in 2" (%) in.. /.. 2 0. 0.2% 0.5% 1.0% (%/hour) Aim Structure Normalized 15% martensite + 85% coarse bainite Oil Quenched 98% martensite + 2% ferrite Middle Pearlite 40% medium fine pearlite + 60% ferrite Upper Bainite 60% upper bainite and acicular ferrite + 40% martensite 302 700 115,000 132 21. O(c) 61.9 0.01580 278 700 267 700 284 700 115,000 289 19.8(c) 115,000 265.2 20.0(c) 115,000 147 20.2(c) 63.3 59.2 62.0 0.01925 0.01950 0.01570 a a a a a a a a a a a a a a a 0.0220 0.0095 0.0120 0. 0180 a jower Bainite 275 700 115,000 59.4 18.8(c) 66.7 95% lower bainite + 5% ferrite Normalized 303 900 70,000 1482(4 - -- 0.00335 a a 24 1400 0.00030 15% martensite + 85% coarse bainite Oil Quenched 272 900 70,000 756 30.3(c) 64.0 0.00378 a a 3 50 0.00384 98% martensite + 2% ferrite Upper Bainite 289 900 70,000 686 30.0(c) 59. 5 0.00355 a a 1 50 0.00504 60% aupper bainite and acicular ferrite + 40% martensite Lower Bainite 283 900 70,000 1456 24.0(c) 56.2 0.00350 a a 12 362 0.00326 95% lower bainite + 5% ferrite Normalized 15% martensite + 85% coarse bainite Oil Quenched 98% martensite + 2% ferrite Upper Pearlite 45% medium pearlite + 55% ferrite Middle Pearlite 40% medium fine pearlite + 60% ferrite 311 1100 306 1100 309 1100 285 1100 20,000 773 2 20,000 666 4.5 19,000 565 4.4 19,000 669() 3 0.00090 0.00101 0.00082 1.6 0.00110 1 46 375 1 13 139 1 17 159 a 10 185 656 345 336 430 0.00086 0.00186 0.00204 0.00145

Aim Structure Lower Pearlite 40% fine pearlite + 60% ferrite Upper Bainite 60% upper bainite and acicular ferrite + 40% martensite Lower Bainite 95% lower bainite + 5% ferrite Normalized 15% martensite + 85% coarse bainite Oil Quenched 98% martensite + 2% ferrite Middle Pearlite 40% medium fine pearlite + 60% ferrite Upper Bainite 60% upper bainite and acicular ferrite + 40% martensite Middle Bainite 100% fine acicular bainite Lower Bainite 95% lower bainite + 5% ferrite BHN 313 327 Temperature (IF) 1100 1100 Stress Rupture Time (psi) (hours) 19,000 550 19,000 796 TABLE V, Continued Elong- Reduction Deformation Time to Reach Specified Total Deformations ation of Area on Loading % in" () (in./in.) 0.1% 0.2% 0. 5% 1.0% 11.5 15.2 0.00093 a 10 79 194 5.8(c) 6.6 0.00110 a 8 177 447 302 1100 313 1200 310 1200 276 1200 320 1200 310 1200 273 1200 19,000 7,500 7,500 7,500 7,500 7,500 7,500 - 1040(4 918 575(f) 1033 456 812 709 10.0 30.0 10(e) 22. 5(c) 19. 1(e)(c) 22.9(c) 0.00127 14.9 0.00046 39.8 0.00058 - 0.00034 35.8 0.00054 a 18 104 281 6 46 176 333 6 17 69 144 10 46 196 370 1 8 45 104 10 26 115 228 6 30 112 229 I Minimum Creep Rate (%/hour) 0.00400 0.00140 0.00146 0.00230 0.00660 0.00198 0..00810 0.00316 0.00360 34.6 0.00050 0.00048 (a) Specimen reached this deformation on loading. (b) Extrapolated value. (c) 0. 250-inch diameter specimen, elongation % in 1-inch. (d) Test discontinued at this time. (e) Very badly scaled. (f) Broke in gage mark.

UNIVERSITY OF MICHIGAN 3 015 527 0019