nickel base superalloys in which critical amounts of boron are employed to enhance creep-rupture strength and ductility in the 1,300° F.-1,800° F. temperature range. Creep-rupture strength and ductility at temperatures around 1,800° F. also is enhanced by employing amounts of carbon below a critical upper limit. These alloys are particularly useful in the form of castings as gas turbine engine components.
|
61. A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. 22. A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 40% to 80% by weight..Baddend. .Badd. 41. A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy..Baddend. .Badd. 27. A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy..Baddend. .Badd. 50. A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight..Baddend. .Badd. 36. A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 40% to 80% by weight..Baddend. .Badd. 13. A shaped object of the alloy of claim .Badd.1.Baddend. 12 capable of withstanding an applied stress of 29,000 psi at 1,800° F. without rupture for a time in excess of 40 hours. .Badd.
12. A shaped object of the alloy of claim .Badd.1 .Baddend.50 capable of withstanding an applied stress of 94,000 psi at 1,400° F. without rupture for a time in excess of 120 hours. .Badd.
14. The alloy of claim .Badd.1.Baddend. 50 which contains, on a weight basis, about 6.0% to about 17% chromium, about 2% to about 8% aluminum, about 0.75% to about 3% titanium, about 2% to about 17% cobalt, and about 40% to 80% by weight
nickel. .Badd. 18. The alloy of claim .Badd.1.Baddend. 50 which contains, on a weight basis, about 5% to 12% chromium, about 4% to about 8% aluminum, about 0.75% to about 2.5% titanium, about 5% to about 15.5% cobalt, and about 40% to 80% by weight nickel. .Badd.
1. A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight..Baddend. 2. The nickel base alloy of
3. The nickel base alloy of
4. A cast component for use in a gas turbine engine formed of the alloy of
5. The component of
6. The component of
7. The component of
8. A cast component for use in a gas turbine engine formed of the alloy of
9. The component of
10. The component of
11. The component of
15. The nickel base alloy of
16. A cast component for use in a gas turbine engine formed of the alloy of
17. A cast component for use in a gas turbine engine formed of the alloy of
19. The nickel base alloy of
20. A cast component for use in a gas turbine engine formed of the alloy of
21. A cast component for use in a gas turbine engine formed of the alloy of
23. The nickel base alloy of
24. The nickel base alloy of
25. A cast component for use in a gas turbine engine formed of the alloy of
26. A cast component for use in gas turbine engine formed of the alloy of
28. The nickel base alloy of
about 0.25% by weight..Baddend. .Badd. 29. The nickel base alloy of
30. A cast component for use in a gas turbine engine formed of the alloy of
31. The component of
32. A cast component for use in a gas turbine engine formed of the alloy of
33. The component of
34. A shaped object of the alloy of
35. A shaped object of the alloy of
37. The nickel base alloy of
38. The nickel base alloy of
39. A cast component for use in a gas turbine engine formed of the alloy of
40. A cast component for use in a gas turbine engine formed of the alloy of
42. The nickel base alloy of
43. The nickel base alloy of
weight..Baddend. .Badd. 44. A cast component for use in a gas turbine engine formed of the alloy of
45. The component of
46. A cast component for use in a gas turbine engine formed of the alloy of
47. The component of
48. A shaped object of the alloy of
49. A shaped object of the alloy of
51. The nickel base alloy of
52. The nickel base alloy of
54. The nickel base alloy of
55. The nickel base alloy of
56. The nickel base alloy of
cobalt. 57. A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. 58. The nickel base alloy of claim 57 wherein the tungsten and vanadium contents are essentially 0. 59. A cast component for use in a gas turbine engine formed of the alloy of claim 57. 60. The nickel base alloy of claim 57 wherein the carbon content is no more than 0.025% by weight. 63. The nickel base alloy of
67. The alloy of
68. The alloy of
to about 10% tantalum, and 0 to about 2.5% tungsten. 69. .Badd.A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. .Baddend. 70. .Badd.The nickel base alloy of claim 69 wherein the carbon content is less than 0.02% by weight. .Baddend. 71. .Badd.The nickel base alloy of claim 69 wherein the molybdenum content is 0.00-3% and the tungsten content is 5-20%. .Baddend. 2. .Badd.The nickel base alloy of claim 69 wherein the molybdenum content is 3-8%, the tungsten content is < 2.5%, and the tantalum content is 2.3-10%. .Baddend. 73. .Badd.The nickel base alloy of claim 69 wherein the cobalt content is 5 to 15.5% cobalt. .Baddend. 74. .Badd.The nickel base alloy of claim 73 wherein the molybdenum content is < 3. .Baddend. 75. .Badd.The nickel base alloy of claim 74 wherein the chromium content is 5-12% and the tungsten content is 5-20%. .Baddend. 76. .Badd.The alloy of claim 74, which contains, on a weight basis, about 2.3% to about 10% tantalum. .Baddend. 77. .Badd.The alloy of claim 76 which contains, on a weight basis, 5-20% tungsten. .Baddend. 78. .Badd.The alloy of claim 74, which contains, on a weight basis, less than 3% tantalum. .Baddend. 79. .Badd.The alloy of claim 69 which contains, on a weight basis, about 6.0% to about 17% chromium, about 2% to about 8% aluminum, and about 40% to 80% by weight nickel. .Baddend. 80. .Badd.The nickel base alloy of claim 79 wherein the carbon content is no more than 0.025% by weight. .Baddend. 81. .Badd.The alloy of claim 79 which contains, on a weight basis, 0 to about 3% molybdenum, 0 to about 3% tantalum, about 11% to about 16% tungsten, and about 0.001 to about 0.5% zirconium. .Baddend. .Badd.The alloy of claim 69 which contains, on a weight basis, about 5% to 12% chromium, about 4% to about 8% aluminum, about 5% to about 15.5% cobalt, and about 40% to 80% by weight nickel. .Baddend. 83. .Badd.The nickel base alloy of claim 82 wherein the carbon content is no more than 0.025% by weight. .Baddend. 84. .Badd.The alloy of claim 82 which contains, on a weight basis, about 3% to about 8% molybdenum, about 2.3% to about 10% tantalum, and 0 to about 2.5% tungsten. .Baddend. 85. .Badd.A cast component for use in a gas turbine engine formed of the alloy of claim 69. .Baddend. 86. .Badd.A shaped object of the alloy of claim 69 capable of withstanding an applied stress of 94,000 psi at 1,400° F. without rupture for a time in excess of 120 hours. .Baddend. 87. .Badd.The nickel base alloy of claim 69 wherein the following elements are in the weight percent ranges set forth:
88. .Badd.The nickel base alloy of claim 69 wherein the following elements are in the weight percent ranges set forth:
89. .Badd.A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight, said boron and carbon contents being effective to enhance creep-rupture strength and ductility of said alloy in the 1300° F to 1500° F temperature range without substantially deleteriously affecting creep-rupture strength and ductility of said alloy at temperatures in the 1700° F to 1900° F range. .Baddend. 90. .Badd.A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. .Baddend. 91. .Badd.The nickel base alloy of claim 90 wherein the boron content is about 0.07% to about 0.25% by weight. .Baddend. 92. .Badd.The nickel base alloy of claim 90 wherein the carbon content is less than 0.02% by weight. .Baddend. 93. .Badd.A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. .Baddend. 94. .Badd.The nickel base alloy of claim 93, which contains, on a weight basis, about 5 to about 15.5 cobalt and < 3 molybdenum. .Baddend. 95. .Badd.The alloy of claim 94, which contains, on a weight basis, 5-20% tungsten. .Baddend. 96. .Badd.The nickel base alloy of claim 93 wherein the molybdenum content is 3-8% and the tungsten content is 0 to 2.5%. .Baddend. 97. .Badd.The alloy of claim 96 which contains, on a weight basis, about 5% to 12% chromium, about 4% to about 8% aluminum, about 5% to about 15.5% cobalt, and about 40% to 80% by weight nickel. .Baddend. 98. .Badd.The nickel base alloy of claim 97 which contains, on a weight basis, 0 to 0.2 columbium. .Baddend. 99. .Badd.The nickel base alloy of claim 97 wherein the following elements are in the weight percent ranges set forth:
100. .Badd.A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. .Baddend. 101. .Badd.The nickel base alloy of claim 100 wherein said boron and carbon contents are effective to enhance creep-rupture strength and ductility of said alloy in the 1300° F. to 1500° F. temperature range without substantially deleteriously affecting creep-rupture strength and ductility of said alloy at temperatures in the 1700° F. to 1900° F. range. .Baddend. 02. .Badd.The nickel base alloy of claim 100 wherein the carbon content is less than 0.02% by weight. .Baddend. 103. .Badd.A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. .Baddend. 104. .Badd.The nickel base alloy of claim 103 wherein the boron content is about 0.07% to about 0.25% by weight. .Baddend. 105. .Badd.The nickel base alloy of claim 103 wherein the carbon content is less than 0.02% by weight. .Baddend. 106. .Badd.A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. .Baddend. 107. .Badd.The nickel base alloy of claim 106 wherein the boron content is about 0.07% to about 0.25% by weight. .Baddend. 108. .Badd.The nickel base alloy of claim 106 wherein the carbon content is less than 0.02% by weight. .Baddend. 109. .Badd.A nickel base alloy for use at relatively high temperatures consisting essentially of the following elements in the weight percent ranges set forth:
the balance of the alloy being essentially nickel and minor amounts of impurities and incidental elements which do not detrimentally affect the basic characteristics of the alloy, said nickel being present in an amount of from about 35% to 85% by weight. .Baddend. 110. .Badd.The nickel base alloy of claim 109 wherein the boron content is about 0.07% to about 0.25% by weight. .Baddend. 111. .Badd.The nickel base alloy of claim 109 wherein the carbon content is less than 0.02% by weight. |
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This invention relates to nickel-base alloys having relatively great tensile strength at high temperatures and to castings made from such alloys. The nickel-base superalloys of the present invention are particularly useful for fabricating components of gas turbine engines, such as turbine blades, turbine vanes, integral wheels, and the like.
There are a number of precipitation strengthened nickel-base superalloys which, because of their strength at high temperatures, are used as materials in fabricating components for use in high temperature sections of gas turbines. The precipitate involved is an intermetallic compound, generally referred to as gamma prime, having the generic formula (Ni3 (Al, Ti). Alloys hardened by such precipitates are referred to as gamma prime strengthened superalloys. In recent years, while characteristics of such alloys at lower temperatures have not altogether been ignored, the greater emphasis in the development of improved alloys has been centered around performance at high temperatures. High temperature performance has been of concern because of the fact that in new engine designs, as calss .Badd.class .Baddend.of engines is the hot section or turbine blade. Because of the severe conditions of temperature and stress to which these components are subjected, they must be formed of high strength superalloys.
Usual designs involve the mechanical attachment of turbine blades around the periphery of a wheel or disk which rotates at high speed. In operation, hot gases pass over the airfoil portion of the blades, causing the blades and disk to rotate at high speed. The hot gases raise the metal temperatures and the high rotational speed of the disk imposes stress due to centrifugal loading. The attachment, or root portion of the blade is heated only to moderate temperatures due to the cooling effect of the massive disk. The temperature to which the root section of the blade is heated is frequently in the ductility trough temperature range (1,300° F. to 1,500° F.). It is an essential mechanical property of an alloy being used for such blades that it be capable of deforming predictably in the root section at temperatures around 1,400° F. while withstanding mechanically imposed strain without cracking, i.e., the alloy must possess reasonable ductility. The alloys of the present invention, containing boron within the critical range of 0.05% to 0.30% by weight, demonstrate great advantage in strength and ductility in the 1,400° F. temperature range over prior art alloys intended for use in turbine blades.
The rotating turbine disk, to which the blade root is attached, also requires high resistance to creep and rupture along with ductility and strength to resist fatigue and crack propagation. Accordingly, the alloys described herein provide enhanced properties desirable in disk alloys.
Manufacturers of small gas turbine engines generally employ an integral wheel rather than an assembly of individual disks and blades. These integral wheels, consisting of a single component comprising a disk having radially extending blade airfoils at the disk periphery, is usually manufactured by investment casting. Normal modes of operation for small engines subject such components to rapid heating and cooling. This normal mode of operation results in premature cracking at the disk rim between the blade airfoils, because of low cycle thermal and mechanical fatigue. Since the disk rin in many engine designs operates up to about 1,400° F., the alloys of the present invention enhance the overall performance of integral wheels.
The formulations of several of the more important prior art alloys which are currently commercially used in turbine engines are tabulated in Table II. The values tabulated represent the amount of each ingredient present in terms of weight percent. The amount of boron and carbon present in each formulation is considered by the prior art to be approximately optimum. With respect to each of the alloys, designated A, B, C, D, E, and F, the U.S. Patent and commercial designation is indicated in the table.
For purposes of comparison, example alloys, compositionally similar to the commercial alloys of Table II, but containing boron within the critical range of the present invention, were prepared. Analyses of these example alloys (designated A-1, B-1, etc.) are presented in Table III. Standard cast-to-size test bars (0.25 inch in diameter) of the alloys of Table II and the example alloys of Table III were prepared by melting and casting under vacuum into shell molds. All example alloy specimens were heat treated under a protective atmosphere at 1,975° F. for four hours and then air cooled. The example alloys were also subjected to an aging heat treatment at 1,650° F. for ten hours. Each of the commercial alloys of Table II was heat treated in accordance with the practice recommended by the alloy developer.
Table IV shows the comparative creep-rupture strength (as measured by time to rupture) and ductility, (as measured by prior creep) of both commercial alloys A, B, C, and E, and example alloys A-1, B-1, C-1, C-2, C-3 and E-1. All alloys were tested at 1,400° F. under a stress of 94,000 psi.
The data in Table IV shows a very significant improvement in both 1,400° F. creep-rupture strength and ductility for alloys having a boron content within the critical range of the present invention. At 0.20 weight percent boron, the properties of Example C-3, although decreasing from Example C-2, still show a marked improvement over Alloy C.
The data set forth in Tables II-IV demonstrates that the utility of nickel-base superalloys for use in gas turbine engine components in which maximum service temperature does not exceed about 1,400° F. is greatly enhanced by increasing boron content to an effective level previously considered excessive.
| TABLE II |
| ______________________________________ |
| A* B* C* D* E* F* |
| ______________________________________ |
| C 0.10 0.10 0.15 0.15 0.18 0.21 |
| Cr 8.0 10.0 9.0 9.0 10.0 12.5 |
| Co 10.0 10.0 10.0 10.0 15.0 9.0 |
| W -- -- 12.5 10.0 -- 3.9 |
| .Badd. Mo.Baddend. |
| 6.0 3.0 -- 2.5 3.0 2.0 |
| o |
| Ta 4.25 7.0 -- 1.5 -- 3.9 |
| Ti 1.0 1.0 2.0 1.5 4.7 4.2 |
| Al 6.0 6.0 5.0 5.5 5.5 3.2 |
| B 0.015 0.015 0.015 0.015 0.015 0.02 |
| Zr 0.10 0.10 0.05 0.05 0.06 0.10 |
| Cb -- -- 1.0 -- -- -- |
| V -- -- -- -- 1.0 -- |
| Ni (1) (1) (1) (1) (1) (1) |
| ______________________________________ |
| A* 3,310,399 B-1900 |
| B* 3,310,399 B-1910 |
| C* 3,164,465 MAR-M200 |
| D* 3,164,465 MAR-M246 |
| E* 3,061,426 IN-100 |
| F* 3,619,182 IN-792 |
| (1) Balance |
| TABLE III |
| ______________________________________ |
| EXAMPLE NO. |
| A-1 B-1 C-1 C-2 C-3 E-1 |
| ______________________________________ |
| C 0.12 0.11 0.15 0.09 0.15 0.18 |
| Cr 7.87 10.2 8.75 9.30 8.75 10.1 |
| Co 10.15 10.0 10.1 10.3 10.1 15.1 |
| W -- -- 12.0 12.81 12.0 -- |
| Mo 6.06 3.05 -- -- -- 3.01 |
| Ta 4.40 6.75 -- -- -- -- |
| Ti 1.08 1.12 1.98 2.08 1.98 4.80 |
| Al 5.95 6.30 4.99 4.80 4.99 5.33 |
| B 0.10 0.10 0.10 0.13 0.20 0.10 |
| Zr 0.05 0.14 0.06 0.03 0.06 0.06 |
| Cb -- -- 1.23 1.20 1.23 -- |
| V -- -- -- -- -- 0.86 |
| Ni (1) (1) (1) (1) (1) (1) |
| ______________________________________ |
| (1) Balance |
| TABLE IV |
| ______________________________________ |
| Creep-Rupture Properties |
| 1400F./94,000 psi |
| Boron Content |
| Rupture Life |
| Prior Creep |
| wt. %) (hr.) (%) |
| ______________________________________ |
| Alloy A 0.016 31.0 1.98 |
| Example No.: |
| A-1 0.10 229.6 6.80 |
| Alloy B 0.015 102.1 3.68 |
| Example No.: |
| B-1 0.10 297.2 8.95 |
| Alloy C 0.015 46.7 0.51 |
| Example No.: |
| C-1 0.10 400.6 3.60 |
| C-2 0.13 442.6 6.45 |
| C-3 0.20 245.5 2.35 |
| Alloy E 0.012 26.6 0.96 |
| Example No.: |
| F-1 0.10 345.0 5.25 |
| ______________________________________ |
| Prior creep indicates the last creep reading prior to specimen failure |
The need for improved higher temperature (greater than 1,700° F.) creep capability in gas turbine alloys is of comparable importance to effecting an improvement in 1,400° F. creep-rupture strength and ductility. Therefore, the effect of the high boron range upon the creep-rupture properties in the 1,700° F. to 1,900° F. temperature range was studied by conducting creep-rupture tests on heat treated standard cast-to-size test bars at 1,800° F. under a stress of 29,000 psi.
Results of that testing show that the high boron levels, demonstrated as being unusually effective for 1,400° F. properties, were deleterious to 1,800° F. rupture strength. The effect was a weakening of the resistance of all alloys in Table II to creep deformation and a noticeable increase in ductility, i.e., a weaker but more ductile material. For gas turbine components requiring both 1,400° F. and 1,800° F. creep-rupture strength and ductility, use of the alloys shown in Table II would involve the unacceptable tradeoff of improved 1,400° F. ductility at the expense of decreased 1,800° F. strength.
It has been discovered, in further accord with the present invention, that by reducing the carbon content to a critical upper limit of no more than about 0.05 weight percent, it is possible to both effect the improvement in 1,400° F. properties and approximately maintain, and in some cases improve, creep-rupture strength and ductility at 1,800° F. Alloys of the present invention, containing less than 0.05 weight percent carbon are capable of withstanding an applied stress of 29,000 psi at 1,800° F. without rupture for a time in excess of 40 hours.
The low carbon aspect of the present invention is particularly important with respect to turbine components requiring enhanced properties at both 1,400° F. and 1,800° F. As previously noted, properties at around 1,400° F. are particularly important with respect to the root sections of turbine blades. However, the hot gases passing across the airfoil portion of the blade raise metal temperatures into the 1,700° F. to 1,900° F. temperature range. Accordingly, turbine blades desirably require an alloy having good high temperature properties throughout the temperature range of from about 1,300° F. to about 1,900° F. or higher.
To demonstrate the utility and advantages of the low carbon feature of the present invention, thirty pound heats of example alloys A-2, B-2, C-4 through D-1, E-2 through 9, and F-1 were prepared by melting under vacuum. Standard test bars (0.25 inch diameter) were cast under vacuum into shell molds and all specimens were heat treated under a protective atmosphere at 1,975° F. for four hours. After air cooling, all specimens were subjected to an aging heat treatment of 1,650° F. for ten hours. Analyses for series A,B,D, and F example alloys are shown in Table V. Analyses for series C and E example alloys are shown, respectively, in Tables IV and VII. In all six series compositions, carbon has been reduced to as low a level as possible using normal master alloys and metals in the preparation of each heat. Such a technique is representative of typical commercial practice. Intentional carbon was added however, where appropriate, to determinate the critical upper limit.
Creep-rupture tests were conducted at 1,800° F. under a stress of 29,000 psi and at 1,400° F. under a stress of 94,000 psi on all low carbon example alloys. For comparative purposes, the same tests were conducted on the commercial alloys of A,B,C,D,E, and F of Table II. The commercial alloy test bars were heat treated in accordance with the procedures recommended by the producers to achieve maximum mechanical properties. Creep-rupture data for commercial alloys D and F under these conditions were obtained from technical literature provided by the respective alloy producers.
The data of Table VII demonstrates the applicability of the present invention to a wide range of superalloys. The four example alloys corresponding to the four commercial alloys designated A,B,D, and F had boron and carbon levels approaching the target compositions, i.e., 0.01 weight percent carbon and 0.10 and 0.12 weight percent boron. The comparative test results between the commercial alloys A, B, D, and F and corresponding series A, B, D and F example alloys set forth in Table VIII shows in all cases that very significant improvements are effected at both 1,400° F. and 1,800° F. in rupture life and ductility.
| TABLE V |
| ______________________________________ |
| EXAMPLE NO. |
| A-2 B-2 D-1 F-1 |
| ______________________________________ |
| C 0.014 0.040 0.009 0.009 |
| Cr 9.75 10.56 9.66 11.35 |
| Co 12.15 11.76 10.91 9.43 |
| W -- -- 9.66 4.18 |
| Mo 5.89 3.10 2.43 2.04 |
| Ta 3.71 5.70 1.50 4.23 |
| Ti 0.96 0.99 1.38 3.69 |
| Al 5.95 6.03 5.19 3.92 |
| B 0.081 0.109 0.084 0.096 |
| Zr 0.073 0.084 0.062 0.083 |
| Ni (1) (1) (1) (1) |
| ______________________________________ |
| (1) Balance |
| TABLE VI |
| __________________________________________________________________________ |
| EXAMPLE NO. |
| C-4 C-5 C-6 C-7 C-8 C-9 C-10 |
| C-11 |
| C-12 |
| C-13 |
| __________________________________________________________________________ |
| C 0.011 |
| 0.010 |
| 0.014 |
| 0.012 |
| 0.011 |
| 0.018 |
| 0.018 |
| 0.045 |
| 0.023 |
| 0.033 |
| Cr 9.33 |
| 8.33 |
| 8.89 |
| 8.61 |
| 8.64 |
| 8.97 |
| 8.96 |
| 9.50 |
| 9.54 |
| 10.00 |
| Co 10.66 |
| 10.70 |
| 10.64 |
| 10.66 |
| 10.71 |
| 10.78 |
| 10.60 |
| 10.50 |
| 10.69 |
| 10.54 |
| W 12.41 |
| 12.40 |
| 12.74 |
| 12.84 |
| 12.48 |
| 12.55 |
| 12.41 |
| 12.5 |
| 11.84 |
| 13.15 |
| Ti 1.76 |
| 1.78 |
| 1.77 |
| 1.78 |
| 1.75 |
| 1.77 |
| 1.76 |
| 2.0 1.75 |
| 1.75 |
| Al 5.65 |
| 5.53 |
| 5.63 |
| 5.80 |
| 5.41 |
| 5.13 |
| 5.15 |
| 4.98 |
| 4.76 |
| 4.76 |
| B 0.02 |
| 0.03 |
| 0.08 |
| 0.14 |
| 0.15 |
| 0.20 |
| 0.235 |
| 0.10 |
| 0.28 |
| 0.39 |
| Zr 0.077 |
| 0.075 |
| 0.079 |
| 0.068 |
| 0.074 |
| 0.065 |
| 0.054 |
| 0.060 |
| 0.053 |
| 0.038 |
| Cb 0.95 |
| 0.95 |
| 0.92 |
| 0.92 |
| 0.92 |
| 0.91 |
| 0.85 |
| 1.09 |
| 0.88 |
| 0.79 |
| Ni (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) |
| __________________________________________________________________________ |
| (1) Balance |
| TABLE VII |
| __________________________________________________________________________ |
| EXAMPLE NO. |
| E-2 E-3 E-4 E-5 E-6 E-7 E-8 E-9 |
| __________________________________________________________________________ |
| C 0.010 |
| 0.008 |
| 0.008 |
| 0.008 |
| 0.010 |
| 0.011 |
| 0.012 |
| 0.012 |
| Cr 8.56 |
| 9.10 |
| 8.95 9.67 9.87 9.87 |
| 10.22 |
| 10.05 |
| Co 16.60 |
| 16.67 |
| 16.62 |
| 16.62 |
| 16.62 |
| 16.86 |
| 16.80 |
| 16.69 |
| Mo 3.01 |
| 2.94 |
| 3.17 3.06 3.03 3.25 |
| 3.33 |
| 3.32 |
| Ti 4.89 |
| 4.90 |
| 4.88 4.74 4.91 4.64 |
| 4.64 |
| 4.56 |
| Al 5.58 |
| 5.71 |
| 5.60 5.61 5.63 5.22 |
| 5.23 |
| 5.23 |
| B 0.018 |
| 0.044 |
| 0.088 |
| 0.090 |
| 0.125 |
| 0.170 |
| 0.180 |
| 0.220 |
| Zr 0.079 |
| 0.067 |
| 0.074 |
| 0.071 |
| 0.060 |
| 0.067 |
| 0.069 |
| 0.064 |
| V 1.06 |
| 1.07 |
| 1.07 1.08 1.06 0.996 |
| 1.01 |
| 1.01 |
| Ni (1) (1) (1) (1) (1) (1) (1) (1) |
| __________________________________________________________________________ |
| (1) Balance |
| TABLE VIII |
| ______________________________________ |
| Creep-Rupture Properties |
| 1400F./94,000psi |
| 1800F./29,000psi |
| Prior Final |
| Boron Carbon Life Creep Life Elong. |
| (wt. %) |
| (wt. %) (hr.) (%) (hr.) |
| (%) |
| ______________________________________ |
| Alloy A 0.016 0.12 31.0 1.98 53.2 6.0 |
| Example No.: |
| A-2 0.081 0.014 146.5 |
| 7.3 44.8 9.9 |
| Alloy B 0.010 0.11 102.1 |
| 3.68 50.3 9.3 |
| Example No.: |
| B-2 0.109 0.040 206.0 |
| 5.1 52.4 13.0 |
| Alloy D 0.015 0.15 120.0 |
| 2.2 50.0 5.0 |
| Example No.: |
| D-1 0.084 0.009 432.8 |
| 4.3 58.1 4.8 |
| Alloy F 0.02 0.21 62.0 3.5 30.0 11.0 |
| Example No.: |
| l-F-1 0.096 0.009 |
| 254.4 8.1 79.2 11.7 |
| ______________________________________ |
The most pronounced effect noted is with alloy F in which 1,400° F. rupture life is increased by more than a factor of four, while ductility is doubled. At 1,800° F. the time to rupture is more than doubled, an unusually large increase.
Comparative results of the testing between alloy C and the respective Series C example alloys is shown in Table IX. The 1,400° F. results show strength comparable to the previous high carbon alloy results set forth in Table IV. This demonstrates that the boron is effective in improving 1,400° F. properties regardless of carbon level. The 1,800° F. results show creep-rupture life increasing with increasing boron to about 0.15 weight percent. Above 0.15 weight percent boron, strength falls off slightly. Example alloy C-4 shows very good rupture life at 1,400° F., but the low level of both boron and carbon causes low ductility in the 1,800° F. test. In addition, the combination of low boron and low carbon contents causes poor castability and a tendency for castings to crack on cooldown during solidification. The minimum boron required to circumvent these problems in the low carbon alloys is about 0.05 weight percent.
Comparative results of testing between alloy E and the respective Series E example alloys is shown in Table X. In these data it is seen that although the 1,400° F. strength is below the high carbon counterparts reported in Table IV, the improvement over commercial alloy E is significant.
| TABLE IX |
| ______________________________________ |
| Creep-Rupture Properties |
| 1400F./94,000psi |
| 1800F./29,000psi |
| Prior Final |
| Boron Carbon Life Creep Life Elong. |
| (wt. %) |
| (wt. %) (hr.) (%) (hr.) |
| (%) |
| ______________________________________ |
| Alloy C 0.015 0.15 46.7 0.51 96.8 7.5 |
| Example No.: |
| C-4 0.02 0.011 314.8 |
| 3.50 73.6 2.2 |
| C-5 0.03 0.010 392.2 |
| 2.57 85.2 2.4 |
| C-6 0.08 0.014 448.0 |
| 2.36 113.9 |
| 4.2 |
| C-7 0.14 0.012 452.9 |
| 3.53 122.4 |
| 6.0 |
| C-8 0.15 0.011 468.6 |
| 2.21 128.3 |
| 5.8 |
| C-9 0.20 0.018 459.8 |
| 2.03 117.1 |
| 4.5 |
| C-10 0.235 0.018 458.6 |
| 1.57 64.8 4.2 |
| C-11 0.10 0.045 397.2 |
| 2.59 92.3 7.0 |
| C-12 0.28 0.023 347.4 |
| 2.11 43.0 4.6 |
| C-13 0.39 0.033 80.7 1.56 14.7 11.1 |
| ______________________________________ |
| TABLE X |
| ______________________________________ |
| Creep-Rupture Properties |
| 1400F./94,000psi |
| 1800F./29,000psi |
| Prior Final |
| Boron Carbon Life Creep Life Elong. |
| (wt. %) |
| (wt. %) (hr.) (%) (hr.) |
| (%) |
| ______________________________________ |
| Alloy E 0.015 0.18 26.6 0.95 41.9 8.5 |
| Example No.: |
| E-2 0.018 0.010 38.6 2.32 27.0 5.2 |
| E-3 0.044 0.008 68.1 5.44 48.6 11.4 |
| E-4 0.088 0.008 104.2 |
| 5.92 41.3 12.3 |
| E-5 0.090 0.008 117.2 |
| 5.91 38.1 11.7 |
| E-6 0.125 0.010 174.1 |
| 4.86 41.2 13.8 |
| E-7 0.170 0.011 266.3 |
| 5.03 36.5 11.9 |
| E-8 0.180 0.012 302.2 |
| 4.90 31.9 10.1 |
| E-9 0.220 0.012 357.6 |
| 5.50 27.6 11.8 |
| ______________________________________ |
In addition, the 1,800° F. properties are maintained within a boron range of about 0.05 to 0.15 weight percent. At 0.22 weight percent boron in Example alloy E-9, the 1,800° F. strength is about sixty percent that of commercial alloy E.
The creep-rupture data discussed previously and presented in Tables IV, V, VIII, IX and X were developed using standard cast-to-size test bars with a 0.250 inch diameter gage section. To demonstrate that the property enhancement is applicable to turbine components, several turbine blade castings were produced from alloy C-7 and specimens cut from those castings. Testing was conducted under the same temperature and stress conditions previously employed and results are present in Table XI. The data show the expected reduction in capability compared to test bar properties, but the level of strength and ductility are exceptionally attractive for specimens machined from turbine component castings.
Another major concern of gas turbine engine builders in the selection of high temperature materials is the ability of the selected alloy to retain initial or starting properties after long time, high temperature exposure. Example Alloy C-7 cast-to-size test bars were subjected to creep testing at 1,500° F. under a stress of 40,000 psi for 1,000 hours and examined microstructurally. No deleterious phase formation was observed and subsequent creep-rupture testing was conducted at 1,400° F. and 94,000 psi for comparison with the same alloy in the as-heat treated condition.
| TABLE XI |
| ______________________________________ |
| Creep-Rupture Properties |
| 1400F./94,000psi |
| 1800F./29,000psi |
| Life Prior Life Final |
| Specimen No. |
| (hr.) Creep (%) (hr.) Elong. (%) |
| ______________________________________ |
| 1 371.9 4.36 42.5 4.5 |
| 2 264.4 3.38 63.3 7.1 |
| 3 172.4 2.00 54.4 5.1 |
| 4 281.5 3.50 39.6 11.4 |
| 5 49.4 7.2 |
| b 46.1 11.5 |
| ______________________________________ |
| TABLE XII |
| ______________________________________ |
| Creep-Rupture |
| Properties |
| 1400F./94,000psi |
| Life Prior |
| Example No. |
| Specimen Condition |
| (hr.) Creep (%) |
| ______________________________________ |
| C-7 As-heat treated |
| 452.9 3.53 |
| C-7 Heat treated plus |
| 463.3 4.03 |
| 1500F exposure for |
| 1000 hours under |
| stress of 40,000psi |
| ______________________________________ |
Results shown in Table XII reveal essentially no change in rupture life and an improvement in 1,400° F. ductility.
FIG. 1 shows the creep characteristics of typical Alloy C and one of the example alloy C-7 test bars in the 1,400° F. test. In FIG. 1, percent creep elongation is plotted against time. The improved results obtained with the alloys of the present invention are dramatically demonstrated.
FIGS. 2 and 3 further demonstrate the critical relationship between boron content and strength and ductility. FIG. 2 is a plot of creep rupture life in hours against the boron content in weight percent of C series, low carbon (less than 0.05% by weight), alloys at both 1,400° F. -94,000 psi and 1,800° F. - 29,000 psi. The creep rupture life for commercial alloy C at 1,400° F. - 94,000 psi and 1,800° F. - 29,000 psi for commercial alloy C is noted on the plot at, respectively, points A and B. As is apparent, substantial improvements in creep rupture life are obtained at 1,400° F. by maintaining the boron content within the critical range of the present invention.
FIG. 3 is a plot of percent creep elongation against boron content for C series, low carbon alloys at both 1,400° F. - 94,000 psi and 1,800° F. - 29,000 psi. The percent creep elongation for commercial alloy C at both 1,400° F. - 94,000 psi and 1,800° F. - 29,000 psi is also noted on this plot, respectively, at points A and B. Again substantial improvements are apparent at 1,400° F. with respect to alloys containing boron within the critical range of the present invention. While the percent creep elongation obtained at 1,800° F. with alloys within the ambit of the present invention is not as high as that of the commercial alloy, highly acceptable levels are achieved.
Metallographic examination was conducted in an attempt to explain the mechanism responsible for the observed property enhancement. FIG. 4 shows the normal microstructure of commercial Alloy C in the as-cast condition at 300 magnifications. The light etching dendrite arms or branch-like areas indicate tungsten segregation. A few titanium rich carbides are visible in the lower center portion of the photomicrograph.
The photomicrograph of FIG. 5 also at 300 magnifications, shows the profound microstructural change resulting from the added boron and reduced carbon of example alloy C-7. Reducing carbon to less than 0.02 weight percent frees titanium previously tied up as a stable carbide. The increased available titanium in the alloy results in the formation of gamma-gamma prime eutectic in the grain boundaries, a microstructural effect known to enhance 1,400° F. ductility. The boron addition results in the formation of discrete grain bondary particles, identified by electron-beam micro-probe analysis as an M3 B2 type boride where M (in the C alloy series) is chromium and tungsten. These grain boundary particles are responsible for restoring 1,800° F. creep-rupture ductility to low carbon alloys.
Electron photomicrographs of commercial alloy C and example alloy C-7, at 7,000 magnifications, are shown, respectively, in FIGS. 6 and 7. FIG. 6 shows, as previously stated to be the general case, borides located at the grain boundaries. In FIG. 7, a boride precipitate within each gamma prime particle may be observed, a phenomenon absent in superalloys of the more conventional compositions. The presence of the very fine boride particles appears to retard dislocation movement through the gamma-prime particles and, in essence, provides dispersion strengthening for improved resistance to creep deformation at 1,800° F. This microstructural effect has not been observed in commercial alloys.
Many of the alloys of the present invention may be extruded and hot forged. Wrought, high strength nickel-base superalloys are generally employed in applications where ductility and fracture roughness in the 1,000° F. to 1,500° F. temperature range are of prime concern. Such applications include gas turbine engine turbine and compressor disks. The series E alloys of the present invention may be hot forged, using conventional techniques, into shaped articles having the characteristics considered to be essential in advanced wrought alloys. For example, alloys E-1 and E-5 have responded very satisfactorily to extrusion and forging in the 2,000° F. to 2,200° F. temperature range in anticipation of the requirements for advanced wrought disk and blade materials.
The present invention also anticipates the use of powder metallurgy for controlling the size, morphology and distribution of the boride microconstituents previously described.
The invention in its broader aspects is not limited to the specific embodiments shown and described. Departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Apr 27 1982 | SORCERY METALS, INC | BALDWIN, JAMES F | SECURITY INTEREST SEE DOCUMENT FOR DETAILS | 003988 | /0491 | |
| May 10 1982 | BALDWIN, JAMES F | SORCERY METALS, INC | ASSIGNMENT OF ASSIGNORS INTEREST | 003985 | /0299 |
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