US3785876A

US3785876A - Treating nickel base alloys

Info

Publication number: US3785876A
Application number: US00291858A
Authority: US
Inventors: R Bailey
Original assignee: Special Metals Corp
Current assignee: ALLEGHENY INTERNATIONAL ACCEPTANCE Corp; TABERT Inc; Special Metals Corp
Priority date: 1972-09-25
Filing date: 1972-09-25
Publication date: 1974-01-15
Anticipated expiration: 1991-01-15
Also published as: IT994765B; FR2200368B1; CA992852A; JPS559943B2; GB1404539A; JPS4970819A; FR2200368A1; DE2348248A1

Abstract

A method of treating a nickel base alloy so as to produce an alloy having a structure characterized by dispersed discrete fine spherical carbides. The method comprises the steps of casting an ingot of nickel base alloy, homogenizing the ingot at a temperature of from 2,200* to 2,400* F so as to dissolve primary carbides present in the alloy and increase the chemical homogeneity thereof; cooling the ingot at least to a temperature of from 1,750* to 2,185* F at a rate which substantially precludes the precipitation of coarse and film-like carbides; and hot working the ingot with the primary carbides in solution with sufficient intensity to cause dispersed discrete fine spherical carbides to precipitate.

Description

United States Patent 1 Bailey TREATING NICKEL BASE ALLOYS [75] Inventor: Ronald E. Bailey, New York Mills,

[73] Assignee: Special Metals Corporation, Ne

Hartford, N.Y.

[22] Filed: Sept. 25, 1972 [21] Appl. No.: 291,858

[52] US. Cl...., 148/2, 148/1 1.5 F [51] Int. Cl. C22f 1/10 [58] Field of Search 148/2, 11.5 R, 11.5 F

[5 6] References Cited UNITED STATES PATENTS 3,329,535 7/1967 Langer et al. 148/1 1.5 F

['111- 3,75,876 Jan. 15, 1974 Primary ExaminerRichard 0. Dean Att0rneyVincent G. Gioia et al.

l 5 ABSTRACT A method of treating a nickel base alloy so as to produce an alloy having a structure characterized by dispersed discrete fine spherical carbides. The method comprises the steps of casting an ingot of nickel base alloy, homogenizing the ingot at a temperature of from 2,200 to 2,400 F so as to dissolve primary carbides present in the alloy and increase the chemical homogeneity thereof; cooling the ingot at least to a temperature of from l,750 to 2,l85 F at a rate whichsubstantially precludes the precipitation of coarse and film-like carbides; and hot working the ingot with the primary carbides in solution with sufficient intensity to cause dispersed discrete fine spherical carbides to precipitate.

'20 Claims, 2 Drawing Figures mmem 15 1914, 3.785.876

FIG. I

TREATING NICKEL BASE ALLOYS The outstanding high temperature properties of nickel base superalloys have made their use in turbines and other high temperature applications quite extensive. However, as in all areas of technology, metallurgists and other scientists and engineers are constantly striving to develop improved alloys. This work has primarily centered around new alloys with dissimilar chemistries, but has also embraced new heat treatments for those already developed, and it is this latter type of work which led to the present invention.

It has commonly been observed that fracture in nickel base super-alloys (particularly in the direction normal to metal flow) occurs by crack propagation along carbide stringers, and this is especially true when the stringers, are associated with remnant dendritic segregation. The stringers which include large elongated carbide particles and aligned discrete carbide particles or a combination of both, provide paths which facilitate fracture.

The present invention provides a sophisticated heat treatment which decreases dendritic segregation and minimizes the formation of carbide stringers. Instead of coarse and/or film-like carbides, it produces a structure characterized by dispersed discrete fine spherical carbides and an alloy with a high degree of chemical homogeneity. As a result the alloy has improved tensile strength and/or tensile ductility and/or stress rupture properties, and particularly in the direction transverse to metal solidification and/or metal flow. More specifically, the invention involves a high homogenization temperature and critically controlled cooling and hot working, as well as casting. Moreover, it is in part based upon processing which was previously considered detrimetal. Previous technical reports have indicated that so called high" homogenization temperatures cause a subsequent formation of carbide films and thereby decrease ductility.

It is accordingly an object of this invention to provide a method of treating nickel base superalloys, so as to improve their properties.

The foregoing and other objects of the invention will be best understood from the following description, reference being had to the accompanying photomicrographs wherein:

FIG. 1 is a photomicrograph at 50X of a billet processed in accordance with the present invention; and

FIG. 2 is aphotomicrograph at 50X of a billet processed in'accordance with prior art techniques.

Nickel base alloys, having a structure characterized by dispersed discrete fine spherical carbides, are pro duced, in accordance with the present invention, by a method which comprises the steps of: casting an ingot of nickel base alloy; homogenizing the ingot at a temperature of from 2,200 to 2,400" F and preferably at a temperature of from 2,250 to 2,400 F, thereby dissolving primary carbides present in the alloy and increasing the chemical homogeneity thereof; cooling the ingot at least to a temperature of from l,750 to 2,185 F at a rate which substantially precludes the precipitation of coarse and film-like carbides; and hot working the ingot with the primary carbides in solution with sufficient intensity to cause dispersed discrete fine spherical carbides to precipitate. The primary carbides are generally MC or M C carbides. MC carbides are comprised of titanium with optional amounts of molybdenum, nickel, chromium and zirconium, and M C carbides are comprised of molybdenum with optional amounts of tungsten, chromium, iron and cobalt. It is essential to dissolve the primary carbides in order for the desired dispersed discrete fine spherical carbides to form during hot working, and in order to do so homogenization must be at a temperature of at least 2,200 F. A maximum homogenization temperature of 2,400 F is, however, imporsed as carbides melt at higher temperatures. Prior to the present invention, it was generally accepted that carbide films would subsequently form following homogenization at temperatures as high as 2,200 F, and that these films would detrimentally affect the alloys ductility. For homogenization, a sufficient period of time is preferably allowed for the primary carbides to dissolve and to permit carbon and other elements to diffuse over a distance at least approaching one half the local dendrite-arm spacing. As a general rule the required period for homogenization is in excess of 4 hours, although no specific time period can be set as it is dependent upon the homogenization temperature and the thickness of the ingot. To obtain the desired carbide structure the ingot must hot worked with the primary carbides in solution and with an intensity which results in an overall reduction in area to the cross section of the ingot of a least 20 percent, and preferably at least 30 percent. Moreover, the hot working must occur at a temperature lower than that at which the primary carbides dissolve and within a range of from l,750 to 2,l85 F, and preferably within a range of from l,800 to 2,1 50 F. The ingot tends to excessivley crack at lower hot working temperatures and cannot be uniformly deformed without cracking at higher temperatures. Prior to hot working, the ingot must be cooled to at least its hot working temperature at a rate which substantially precludes the precipitation of coarse and film-like carbides. This cooling rate is in excess of 25 F per hour, and is preferably in excess of F per hour, and moreover, can be to a temperature as low as room temperature. Of course, ingots cooled to room temperature must be reheated for hot working. By hot working, the present invention includes forging, swaging, extrusion, rolling, drawing, pressing and'all other processes known to those skilled in the art. Furthermore hot working temperatures and all other temperatures referred to herein as well as rates involving temperatures are based upon furnace temperatures rather than metal temperatures, as it is more practical to talk about furnace temperatures when discussing production size ingots and billets. Furnace temperatures are lower than metal temperatures during cooling, and cooling as discussed above is a critical part of the present invention. Metal temperatures do, however, reach furnace temperatures during homogenization due to the prolonged exposure at temperature.

The nickel base alloy being treated is most often a gamma prime strengthened alloy and generally, but not necessarily, consists essentially of, in weight percent: up to 0.2 percent carbon, up to 2.0 percent manganese, up to 2 percent silicon, from S to 25 percent chromium, up to 20 percent cobalt, up to 10 percent molybdenum, up to 10.0 percent titanium, up to 5 percent aluminum, up to 0.05 percent boron, up to 0.5 percent zirconium, up to 40.0 percent iron, up to 8.0 percent of metal from .the group consisting of columbium, tantalum and hafnium, up to 2.0 percent vanadium, up to 10 percent tungsten, up to 0.5 percent rhenium, up to 0.02 percent of metal from Group II A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel, said percentage of nickel being at least 40 percent silicon, 19.1 percent chromium, 13.7 percent cobalt, 4.20 percent molybdenum, 3.10 percent titanium, 1.34 percent aluminum, 0.005 percent boron, 0.06 percent zirconium, 0.72 percent iron, balance essentially cent. Within this broad range an alloy which has proven 5 nickel. to be particularly well suited for the treatment of the A number of ingots having a composition, in weight present invention consists essentially of, in weight perpercent, of from 0.05 to 0.07 percent carbon, less than cent, up to 0.15 percent carbon, up to 1.0 pe nt 0.10 percent manganese, less than 0.10 percent silicon, manganese, up to 1.0 percent silicon, from 15-23 per- 18.7 percent to 19.7 chromium, 13.0 to 14.5 percent cent chromium, from to 18 percent cobalt, from 3 10 cobalt, 3.75 to 4.5 percent molybdenum, 2.9 to 3.2 perto 6 percent molybdenum, from 2 to 3.5 percent titacent titanium, 1.30- 1.38 percent aluminum, 0.0040 to nium, from 1 0 to 20 percent aj min n-n from 00025 0.0055 percent bOl'OIl, 0.055 to 0.075 percent Zll'CO- to 0.0125 percent boron, from 0.02 to 0.2 perce i nium, less than 1.50 percent iron, balance essentially conium, up to 2 percent iron, up to 4 percent f meta] nickel, were processed in accordance with prior art from the group consisting of columbium, tantalum and techniques- The ingots were homogenized at a maxihafnium, up to 05 percent vanadium uppto 002 mum temperature of 2,l75 F, subjected to haphazard cent of metal from Group 11 A of the periodic table, up 'i cocPlmg to a temperature of from 15000 to to 0.5 percent of rare earth metal, balance essentially 1,700 cooled to room temperatures therefrom nickel. Another alloy within the broad range for which i hot Worked from 2,1250 F MI/B'inCh octagon there is reason to believe that it is particularly well bluets whfchiwere subeequemly ground to 13% inch suited for the treatment of the present invention, conoctagon bmets; 2 a Photomicrograph at 50X of Sists essentially of, in weight percent, up to 015 one of these billets. Note that the carbides theein are cent carbon, up to 2.0 percent manganese, up to 1.0 Concentrated m bands percent silicon, from 5.0 to 15.0 percent chromium, up Pancake property data for both the alloy treated in to 10.0 percent cobalt, from 2 to 7 percent molybdeaccordance with the present invention and for the avernum, from 1.0 to 3.75 percent titanium, up to 2 percent age of the prior art billets is set forth below in Table 1. aluminum, up to 0.05 percent boron, from 25 to 40 The data which is more indicative of transverse properpercent iron, balance essentially nickel. For purposes ties than longitudinal properties clearly shows the value of definition gamma prime is defined and believed to of the heat treatment of the present invention.

TABLE 1 Stress Rupture Properties Room Temperature 1350Fl80 ksi Tensile Properties 1000F Tensile Properties Notch U.T.S Y.S. Elongation Y.S. Elongation Reduction Life Elongation Reduction U.T.S. (km (k 1%) 0r (ksi) (151) (7 r (hrs) 1% Area Area PRESENT INVENTION 201.0 142.0 25.7 32.3 178.0 136.0 24.5 28.6 39.6 39.2 PRlOR ART 190.4 137.5 18.3 22.0 170.8 125.0 16.4 19.9 43.0 25.0

have, the general composition M (Al and/or Ti and It will be apparent to those skilled in the art that the possibly one or more additional metals from the group comprised of tantalum, columbium, molybdenum and- /or chromium). As used herein, the M portion of the gamma prime is regarded as consisting mainly of nickel with possible one or more metals from the group comprised of chromium, cobalt, molybdenum and iron.

The following examples are illustrative of the invention.

A nickel base alloy ingot was cast and homogenized for 43 hours 0PT.?00Fi l rom tlie Emogenization temperature the ingot was cooled to room temperature at a rate which substantially precluded the precipitation of coarse and film-like carbides and kept the primary carbides in solution. After cooling the ingot was reheated at a temperature of2.125F and worked from a 20 inch ingot to a l4%-inch octagon billet, which was subsequently ground to a 13%-inch octagon billet. Dispersed discrete fine spherical carbides precipitated during hot working. This desirable carbide morphology and distribution is seen in FIG. 1 which is a photomicrograph of the hot worked billet. The composition of the ingot was, in weight percent, 0.05 percent carbon, less than 0.10 percent manganese, less than 0.10 pernovel principles of the invention disclosed herein in connection with specific examples thereof will suggest various other modifications and applications of the same. It is accordingly desired that in construing the breadth of the appended claims they shall not be limited to the specific examples of the invention described herein.

1 claim:

1. A method of treating a nickel base alloy so as to produce an alloy having a structure characterized by dispersed discrete fine spherical carbides, which comprises the step of: casting an ingot of nickel base alloy; homogenizing said ingot at a temperature of from 2,200 to 2,400 F, thereby dissolving primary carbides present in said alloy and increasing the chemical homogeneity thereof; cooling said ingot at least to a temperature of from l,750 to 2,l85 F at a rate which substantially precludes the precipitation of coarse and film-like carbides, said cooling rate being in excess of 25 F per hour; and hot working said ingot with said primary carbides in solution with sufficient intensity to cause dispersed discrete fine spherical carbides to precipitate, said hot working occuring at a temperature lower than that at which said primary carbides dissolve and within a temperature range of from 1,750" to 2,185 F, said hot working resulting in an overall reduction in area to the cross section of the" ingot of at least 20 percent.

2. A method according to claim 1 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.2 percent carbon, up to 2.0 percent manganese, up to 2.0 percent silicon, from 5.0 to 25.0 percent chromium, up to 23 percent cobalt, up to percent molybdenum, up to 10.0 percent titanium, up to 5 percent aluminum, up to 0.05 percent boron,.up to 0.5 percent zirconium, up to 40.0-percent iron, up to 8.0 percent of metal from the groupconsisting of columbium, tantalum and hafnium, up to 2.0 percent vanadium, up to 10 percent tungsten, up to 0.5 percent rhenium, up to 0.02 percent of metal from Group II A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel, said percentage of nickel being at least 1 40 percent. 7 v v v 3. A method according to claim 1 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon, up to 1.0 percent manganese, up to 1.0 percent silicon, from -23 percent chromium, from 10 to 18 percent cobalt, from 3 to 6 per- 1 centrnolybdenum, from 2 to 3.5. percent titanium, from 4. A method according to claim 1 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon,- up to 2.0 percent manganese, up to 1.0 percent silicon, from 5.0 to 15.0 percent chromium, up to 10.0 percent cobalt, from 2 to 7 percent molybdenum, from 1.0 to 3.75 percent titanium, up to 2 percent aluminum, up to 0.05 percent boron, from 25 to 40 percent iron, balance essentially nickel.

5. A method according to claim 1 wherein said nickel s alloy sas mmser s stren hen alloy- 6. A method according to claim 1 wherein said. homogenized ingot is cooled to room temperature with said primary carbides in solution and reheated to said but working, t mpe atu e.- 7 V l,

7. A method according to claim 1 wherein said homogenized ingot is cooled directly to said hot working temperature with saidprimary carbidesin solution.

8. A method according to claim 1 wherein said hot working occurs within a temperature range of from l,800 2,150 F. I V I, v

9. A method according to claim 1 .wherein said overall reduction in area to the cross section of said ingot is at least 30 percent. H I 7 10. A method according to claim 1 wherein said ingot is homogenized for a period of time in excess of .4 hours. H I, 7,

l l. A-method according to claim 1 wherein said ingot is.homogenized at a temperature of at least 2,250 F.

12. A method according to claim 11 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.2 percent carbon, up to 2.0 percent manganese, up to 2.0 percent silicon, from 5.0 to 25.0 per cent chromium, up to 23 percent cobalt, up to 10 percent molybdenum, up to 10.0 percent titanium, up to 5 percent aluminum, up to 0.05 percent boron, up to 0.5 percent zirconium, up to 40.0 percent iron, up to 8,0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to 2.0 percent vanadium, up to 10 percent tungsten, up to 0.5 percent rhenium, up to 0.02 percent of metal from Group 11 A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel, said percentage of nickel being at least 40 percent.

13. A method according to claim 11 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon,- up to 1.0 percent manganese, up to 1.0 percent silicon, from 15-23 percent chromium, from 10 to 18 percent cobalt, from 3 to 6 percent molybdenum, from 2 to 3.5 percent titanium, from 1.0 to 2.0 percent aluminum, from 0.0025 to 0.0125 percent boron, from 0.02 to 0.2 percent zirconium, up to 2 percent iron, up to 4.0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to-0.5 percent vanadium, up to 0.02 percent of metal from Group 11 A of the periodic table, up

to 0.5 percent of rare earth metal, balance essentialy nickel.

15. .A method according to claim 11 wherein said nickel base alloy is a gamma prime strengthened alloy.

16. A method according to claim 1 wherein said cooling rate is in excess of F per hour.

17. A method according to claim 16 wherein said nickel base alloy consists essentially of, weight percent, up to 0.2 percent carbon, up to 2.0 percent manganese, up to 2.0 percent silicon, from 5.0 to 25.0 percent chromium, up to 23 percent cobalt, up to 10 percent molybdenum, up to 10.0 percent titanium, up to 5 percent aluminum, up to 0.05 percent boron, up to 0.5 percent zirconium, up to 40.0 percent iron, up to 8.0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to 2.0 percent vanadium, up to 10 percent tungsten, up to 0.5 percent rhenium, up to 0.02 percent of metal from Group 11 A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel, said percentage of nickel being at least 40 percent.

18. A method according to claim 16 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon, up to 1.0 percent manganese, up to 1.0 percent silicon, from 15-23 percent chromium, from 10 to 18 percent cobalt, from 3 to 6 percent molybdenum, from 2 to 3.5 percent titanium, from 1.0 to 2.0 percent aluminum, 'from 0.0025 to 0.0125 percent boron, from 0.02 to 0.2 percent zirconium, up to 2 percent iron, up to 4.0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to 0.5 percent vanadium, up to 0.02 percent of .metal from Group 11 A of the periodic table, up

from 2 to 7 percent molybdenum, from 1.0 to 3.75 percent titanium, up to 2 percent aluminum, up to 0.05 percent boron, from 25 to 40 percent iron, balance essentially nickel.

20. A method according to claim 16 wherein said nickel base alloy is a gamma prime strengthened alloy. 4: s e s- 1

Claims

2. A method according to claim 1 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.2 percent carbon, up to 2.0 percent manganese, up to 2.0 percent silicon, from 5.0 to 25.0 percent chromium, up to 23 percent cobalt, up to 10 percent molybdenum, up to 10.0 percent titanium, up to 5 percent aluminum, up to 0.05 percent boron, up to 0.5 percent zirconium, up to 40.0 percent iron, up to 8.0 percent of metal from tHe group consisting of columbium, tantalum and hafnium, up to 2.0 percent vanadium, up to 10 percent tungsten, up to 0.5 percent rhenium, up to 0.02 percent of metal from Group II A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel, said percentage of nickel being at least 40 percent.
3. A method according to claim 1 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon, up to 1.0 percent manganese, up to 1.0 percent silicon, from 15-23 percent chromium, from 10 to 18 percent cobalt, from 3 to 6 percent molybdenum, from 2 to 3.5 percent titanium, from 1.0 to 2.0 percent aluminum, from 0.0025 to 0.0125 percent boron, from 0.02 to 0.2 percent zirconium, up to 2 percent iron, up to 4.0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to 0.5 percent vanadium, up to 0.02 percent of metal from Group II A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel.
4. A method according to claim 1 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon, up to 2.0 percent manganese, up to 1.0 percent silicon, from 5.0 to 15.0 percent chromium, up to 10.0 percent cobalt, from 2 to 7 percent molybdenum, from 1.0 to 3.75 percent titanium, up to 2 percent aluminum, up to 0.05 percent boron, from 25 to 40 percent iron, balance essentially nickel.
5. A method according to claim 1 wherein said nickel base alloy is a gamma prime strengthened alloy.
6. A method according to claim 1 wherein said homogenized ingot is cooled to room temperature with said primary carbides in solution and reheated to said hot working temperature.
7. A method according to claim 1 wherein said homogenized ingot is cooled directly to said hot working temperature with said primary carbides in solution.
8. A method according to claim 1 wherein said hot working occurs within a temperature range of from 1,800* - 2,150* F.
9. A method according to claim 1 wherein said overall reduction in area to the cross section of said ingot is at least 30 percent.
10. A method according to claim 1 wherein said ingot is homogenized for a period of time in excess of 4 hours.
11. A method according to claim 1 wherein said ingot is homogenized at a temperature of at least 2,250* F.
12. A method according to claim 11 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.2 percent carbon, up to 2.0 percent manganese, up to 2.0 percent silicon, from 5.0 to 25.0 percent chromium, up to 23 percent cobalt, up to 10 percent molybdenum, up to 10.0 percent titanium, up to 5 percent aluminum, up to 0.05 percent boron, up to 0.5 percent zirconium, up to 40.0 percent iron, up to 8,0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to 2.0 percent vanadium, up to 10 percent tungsten, up to 0.5 percent rhenium, up to 0.02 percent of metal from Group II A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel, said percentage of nickel being at least 40 percent.
13. A method according to claim 11 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon, up to 1.0 percent manganese, up to 1.0 percent silicon, from 15-23 percent chromium, from 10 to 18 percent cobalt, from 3 to 6 percent molybdenum, from 2 to 3.5 percent titanium, from 1.0 to 2.0 percent aluminum, from 0.0025 to 0.0125 percent boron, from 0.02 to 0.2 percent zirconium, up to 2 percent iron, up to 4.0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to 0.5 percent vanadium, up to 0.02 percent of metal from Group II A of the periodic table, up to 0.5 percent of rare earth metal, balance essentialy nickel.
14. A method according to claim 11 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon, up to 2.0 percent manganese, up to 1.0 percent silicon, from 5.0 to 15.0 percent chromium, up to 10.0 percent cobalt, from 2 to 7 percent molybdenum, from 1.0 to 3.75 percent titanium, up to 2 percent aluminum, up to 0.05 boron, from 25 to 40 percent iron, balance essentially nickel.
15. A method according to claim 11 wherein said nickel base alloy is a gamma prime strengthened alloy.
16. A method according to claim 1 wherein said cooling rate is in excess of 70* F per hour.
17. A method according to claim 16 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.2 percent carbon, up to 2.0 percent manganese, up to 2.0 percent silicon, from 5.0 to 25.0 percent chromium, up to 23 percent cobalt, up to 10 percent molybdenum, up to 10.0 percent titanium, up to 5 percent aluminum, up to 0.05 percent boron, up to 0.5 percent zirconium, up to 40.0 percent iron, up to 8.0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to 2.0 percent vanadium, up to 10 percent tungsten, up to 0.5 percent rhenium, up to 0.02 percent of metal from Group II A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel, said percentage of nickel being at least 40 percent.
18. A method according to claim 16 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon, up to 1.0 percent manganese, up to 1.0 percent silicon, from 15-23 percent chromium, from 10 to 18 percent cobalt, from 3 to 6 percent molybdenum, from 2 to 3.5 percent titanium, from 1.0 to 2.0 percent aluminum, from 0.0025 to 0.0125 percent boron, from 0.02 to 0.2 percent zirconium, up to 2 percent iron, up to 4.0 percent of metal from the group consisting of columbium, tantalum and hafnium, up to 0.5 percent vanadium, up to 0.02 percent of metal from Group II A of the periodic table, up to 0.5 percent of rare earth metal, balance essentially nickel.
19. A method according to claim 16 wherein said nickel base alloy consists essentially of, in weight percent, up to 0.15 percent carbon, up to 2.0 percent manganese, up to 1.0 percent silicon, from 5.0 percent to 15.0 percent chromium, up to 10.0 percent cobalt, from 2 to 7 percent molybdenum, from 1.0 to 3.75 percent titanium, up to 2 percent aluminum, up to 0.05 percent boron, from 25 to 40 percent iron, balance essentially nickel.
20. A method according to claim 16 wherein said nickel base alloy is a gamma prime strengthened alloy.