US2977222A - Heat-resisting nickel base alloys - Google Patents

Description

United States Patent HEAT-RESISTING NICKEL BASE ALLOYS Clarence George Bieber, Bayonne, NJ., assignor to The International Nickel Company, Inc., New .York, N.Y., a corporation of Delaware No Drawing. Filed Aug. 22, 1955, Ser. No. 529,926

27 Claims. (c1. 75-171) The present invention relates to special high temperature, heat and stress resisting thermal members which are subjected in use under stress at elevated temperatures to destructive actions of various media, especially to the corrosive action of such media as oxidizing, neutral and reducing atmospheres containing harmful constituents, and to special heat resisting, columbium-free and tungsten-free, nickel-chromium alloys suitable for use as such thermal members. i

Heretofore, the art has endeavored to produce satisfactory high temperature alloys for use as heat and stress resisting thermal members in such heat engines as gas turbines, jet engines and the like. While many alloys 'have been proposed, continual demands by industry for heat engines with higher speed and power capacity have placed more rigorous requirements on thermal members of heat engines, including the requirement that thermal members withstand higher and higher operating temperatures under higher and higher stresses. In addition, such heat and stress resisting thermalmembers must possess, among other things, resistance to creep and resistance to corrosion, erosion, oxidation and pitting'at elevated temperatures as well as being capable of resisting destructive actions of operating media. Under operating conditions, thermal members of gas turbines and jet engines are subjected to various types of stresses, including not only steady or static stresses but .also fluctuating or alternating dynamic stresses which complicate the problem of providing satisfactory alloys for use as thermal members, for example, turbine blades, valves and valve parts, and other component parts of heat engines and the like.

In evaluating alloys for high temperature properties, stress rupture tests at elevated temperatures are usually relied upon. Such a test can comprise subjecting a test specimen of the alloy to a rupture test at a temperature of 1500 F. under a given stress. The time it takes the specimen to rupture, i.e., ts rupture life, under the foregoing conditions is employed to evaluate its behavior under stress in service. It has been proposed that cast alloys be employed in a number of instances but it has been found that the cast alloys had the disadvantage of varying widely in fatigue and creep properties among different castings of the same alloy. Furthermore, .certain types of boron-hardened cast alloys were proposed for use as blade material but were found not completely A 2,971,222. Patented Mar. 28, 19st satisfactory, particularly because the alloys were usually glass brittle at'room temperature and were highly sensitive to breakage in handling and also very sensitive to thermal shock. For these and a number of other reasons, it became necessary to employ'thermal members made of Wrought alloys in many applications. In searching for satisfactory wrought alloys, for example, alloys having a high rupture life at higher and higher temperatures, the art found that it was necessary to incorporate in the alloy very substantial amounts of certain special alloying elements. Under existing world conditions, the art became more cognizant of the fact that a shortage-existed in certain important alloying elements and this led to the classification of these scarce alloying elements as strategic elements. Columbium is considered the most strategic alloying element. The other important strategic but less scarce alloying elements are tungsten and cobalt. While still other alloying elements might be deemed strategic elements, these other elements are much more plentiful and much less strategic. The term strategic elements, as employed herein, refers to the highly strategic elements columbium,'tungsten and/or cobalt. In the search for wrought alloys of exceptionally high properties at elevated temperatures, it was found that the more satisfactory wrought alloys usually contained two or even all three of the aforementioned strategic elements in substantial amounts. Many of these more satisfactory wrought alloys required the presence of the particularly strategic element columbium in an amount which created a potential demand for columbium far exceeding the available supply. A number of alloys required the use of colum bium and/or tungsten in combination with cobalt. In vie-w of the situation requiring the minimum use of strategic elements, the art was placed under pressure .to provide wrought alloys having a high fracture life of,

at least about 150 hours when tested at the relatively high temperature of about 1500 F. under the high stress for this temperature of about30,000 pounds per square inch (p.s.i.) and being suitable for use as therm al'mernbers, for example, in jet engines, which must withstand high stresses at temperatures of the order of 1300 F.

to 1700 F., particularly temperatures of the order of 1500 F. to 1700 R, such as are encountered when a plane is operated under condition-s requiring high speed and/or power. Although many attempts were made to overcome the foregoing difficulties and other difficulties and disadvantages, none, as far as I am aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that the problem confronting the art of providing a high temperature, heat and stress resisting thermal member having a high level of high all-around properties can be solved by employing a special heat resisting, columbium-free, tungsten-free, nickel-chromium alloy containing a combination of elements within special ranges and capable of being fabricated into wrought form by hot working and cold working operations. I

It is an object of the present invention to provide an improved alloy having improved high temperature properties and not requiring the presence of a plurality of strategic alloying elements and particularly not requiring the presence of the extremely strategic alloying element columbium. Another object of the invention is to provide improved heat-treatable, nickel-chromium, high temperature, heat and stress resisting, wrought thermal members suitable for use in jet engines, gas turbines and the like. v The invention also contemplates providing improved heat treated, nickel-chromium, high temperature, heat and stress resisting, wrought thermal members characterized by resistance to the destructive actions of various operating media at high temperatures.

It is a further object of the invention to provide an improved heat and stress resisting, high temperature, nickel-chromium alloy which, in a heat treated, wrought condition, neither requires the presence of the highly strategic alloying element columbium nor the presence of a plurality of strategic elements to achieve a high rupture life of at least about 600 hours, and even 1000 or 1500 hours or more, under a stress of about 30,000 p.s.i. at 1500 F., and a rupture life of at least about 100 hours, and often at least 200 or even 250 hours or more, under a stress of about 25,000 p.s.i. at 1600" F.

It is still another object of the invention to provide .a columbium-free, tunsten-free, heat resisting, Wrought nickel-chromium alloy which is characterized by a level of high temperature properties in a heat treated condition comparable to or even better than the properties of other wrought alloys containing columbium or a plurality of strategic elements.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention provides a novel high temperature, heat and stress resisting thermal member especially adapted for use in heat engines and the like, e.g., jet engines, gas turbines, turbo-superchargers and exhaust gas power-recovery turbines, which is made of a special nickel-chromium-molybdenum-aluminum titanium alloy, which does not require the presence of either of the strategic elements columbium and tunsten and which possesses commercial hotand cold-workable properties enabling its fabrication into wrought members.

The alloys within the scope of the present invention broadly comprise about 5% to 18% or 20% chromium. about 1% to 10% molybdenum, up to about 40% cobalt. about 0.05% to 0.35% carbon and an aluminum plu titanium content of about 3.5% to 8.5% with the ratio of aluminum to titanium being between about 0.5 :1 and about 3:1. not more than about 5% iron and with the balance being essentially nickel. By varying the composi- 'tion of the alloy within the aforesaid ranges, it is possible to obtain various combinations of properties in castings and/r heat treated wrought products. Thus, with a chromium content within the range of about to about 9% and an aluminum plus titanium content of about 5.5% to about 8.5% and less than 10% cobalt, a high level rupture life, especially at high temperatures of the order of 1700 F. to 1800 F.. is generally obtained without using large amounts of cobalt. However. by employing larger amounts of cobalt from about 10% to 40%, improved notched strength at temperatures of the order of about 1350" F. is obtained. In order to provide optimum high temperature strength, including high rupture life at temperatures on the order of about 1500 F., 1600 F. or higher, the alloys contemplated in accordance with the invention may contain minor amounts of boron and zirconium with the boron content ranging from a few ten thousandths of a percent up to about 0.009%, e.g., 0.0002% to 0.009%, and with the zirconium content being within the range of about 0.01%

to about 0.25%. No further improvement in high temperature properties is found in wrought alloys when the boron and zirconium are increased above the foregoing amounts and it is found that the forging temperature range is undesirably restricted. The balance of the alloy is nickel and the nickel plus cobalt content is usually about 50% to about of the alloy. The term balance" as used herein includes small amounts of other incidental elements and impurities commonly present in nickel alloys, for example, silicon, manganese, copper, magnesium, etc. As will be appreciated by those skilled in the art, small amounts of other elements, such as vanadium, cerium, tungsten, etc., may be added to the alloy for purposes well known in the art, including grain refinement, malleabilization, strengthening, etc. With regard to the silicon and manganese contents, it is preferred that each of these elements should not exceed 1% of the alloy content and each should more preferably be maintained below 1% although manganese can be as high as 2% or even 3% and silicon as high as 2%. The copper content of the alloy should be maintained below 2% and preferably below about 0.5% or 1%. Magnesium may advantageously be present in small amounts, e.g., 0.002%, up to about 0.1%. Impurities, such as lead, bismuth, tellurium, sulfur, selenium, arsenic, antimony. etc., should be kept as low as is commercially practicable. It is preferred that the impurities lead, bismuth and tellurium be held to 0.01% maximum of each while sulfur, selenium, arsenic and antimony are preferably maintained below 0.05 and more preferably below 0.02%, of each. When the alloy contemplated by the present invention is characterized as being colurnbium-free and tungsten-free, it is to be understood that this characterization is intended to denote that the strategic elements columbium and tungsten might not be present or deliberately added to achieve the properties described herein. As will be appreciated by those skilled in the art, it is not intended to exclude the presence of either or both of these elements as an incidental element introduced With the raw materials employed to produce the alloy. to treat the molten bath of the alloy, etc. A feature of the alloy provided by the present invention is the fact that the presence of these elements is not required to achieve the properties indicated herein.

The aforedescribed alloys contemplated in accordance with the invention may be hot worked. e.g., by forging, rolling, extruding, etc., into the physical form of thermal members. When desired. thermal members produced in these alloys can be cast directly to shape. In such cases, the boron content of the alloy may be increased to as much as about 0.02%, e.g., about 0.0002% to about 0.02%, and the carbon content may be increased to as much as about 0.5%, e.g., about 0.05% to about 0.5%, with the remainder of the alloy consisting of elements in the ranges set forth hereinbefore. The boron content of the castings should not exceed about 0.02% as otherwise difficulties in welding are encountered. When the carbon content exceeds about 0.5%, it is found that the strength of the castings is detrimentally affected.

Preferably, the aluminum plus titanium content of the alloys contemplated by the present invention will lie in the range of about 5% to about 7% when optimum rupture strength at the service temperature is required. For maximum ductility at the service temperature, the aluminum plus titanium content preferably will be about 4.5% to about 6%. In either of these preferred cases, the ratio of aluminum to titanium preferably will be about 0.821 to about 1.611.

When alloys produced in accordance with the invention are employed in the form of fabricated thermal members heat engines and the like, it is preferred that the wrought alloys be subjected toaheat treatment comprising a high temperature heating in the temperature range of about 2000 F. to about 2400 F. for about at least A hour up to about 8 hours, e.g., about 2 hours, cooling rapidly, e.g., as by air cooling or quenching, and then reheating for at least 1 hour within the temperature range of about 1350 F. to 1800" F. for a period of time not substantially exceeding about 48 hours, e.g., about 4 hours to 24 hours. In general, the temperature employed for the high temperature heat treatment should be increased toward the upper part of the heating range when the aluminum plus titanium content of the alloy is about 5% or more in order to provide the best high temperature properties for the particular alloy. It is also to be noted that the optimum temperature to be employed in the high temperature heating is influenced by the composition and characteristics of the particular alloy being heated. For example, in the high temperature heating, undesirable coarsening of the grains may result. Those skilled in the art will appreciate that the heat treatment, when applied to wrought alloys, may be applied entirely after the alloy has been fabricated into thermal members or may be applied partly before fabrication or during fabrication or partly after fabrication. Thus, the high temperature heating may be applied in combination with the hot working operation. In this instance, the metal will be subjected initially to a high temperature, for example, 2100 F., 2200 F., 2300 F., etc., and then worked rapidly, as for example, by extrusion, in order to finish the hot working operation while the alloy is still at a temperature above about 2000 F., e.g., about 2100 F. In this manner, the heat remaining from the hot working operation is utilized to effect the high temperature heating of the heat treatment. Such a combination of high temperature and hot working may be desirable when fine grain size is important in the application where the wrought thermal member is to be used.

Alloys contemplated in accordance with the invention are highly resistant to oxidation andprovide a highly desirable combination of properties in the temperature range of interest in the heat engine art. Stress rupture tests made on the nickel-chromium alloy provided by the invention have demonstrated that the alloy has a rupture life of at least about 50 or 150 hours or much longer when subjectedto a stress of 30,000 p.s.i. at 1500 F. Thermal members made by hot and/or cold working operations of the heat treated alloy exhibit a high combination of properties, including strength, ductility and resistance to stress, to creep, to rupture, to heat, to corrosion, to erosion, to oxidation, to pitting and to other destructive influences of other various operatingmedia at elevated temperatures.

High cobalt alloys comprise about 12% to 18% chromium, about 20% to,

40% cobalt, about 1% to molybdenum, with an aluminum plus titanium content of about 4.8% to 8.5% and with the ratio of aluminum to titanium being within the range of about 05:1 and about 3:1, preferably about 08:1 and 1.6:1, about 0.05% to about 0.35% carbon, up to about 5% iron, and the balance essentially nickel. More preferred high cobalt alloys comprise about 14% to about 17% chromium, about 23% to 35% cobalt,

especially about 23% to about 30% cobalt," about 2% to.4% molybdenum, ab,out,,5.% to 7 %,.Q .,al,t1minum plus titanium with the ratio .of

aluminum to titanium being between about 0.8:1 and 1.611, about 0.10% to about 0.25% carbon and the balance essentially nickel.

The afored'escribed high cobalt alloys preferably contain small amounts of boron and zirconium in order to provide optimum strength at elevated temperatures.

When employed in the wrought condition, the alloys contain about 0.0002% to 0.009% boron and about 0.01% to about 0.25% zirconium. Preferably, the alloys will contain about 0.0004% to 0.007% boron and 0.01% to 0.15% zirconium or, more preferably, about 0.0005% to 0.005% boron and about 0.03% to about 0.08% zirconium. It is to be understood that the aforedescribed preferred high cobalt alloys are malleable and can be produced in the form of wrought thermalmembers in the absence of boron or zirconium. When it is desired to produce the preferred high cobalt alloys in the form of castings, the boron content can be increased to a value as high as 0.02% and the carbon content may be within the range of about 0.05% to about 0.5%. Those skilled in the art are aware that, in generaLcast articles made of high temperature alloys possess superior high temperature strength properties as compared to wrought articles of'the same or substantially the same composition. However, a practical drawback existing with the production of the castings is the lack of uniformity which has beenfound to characterize finished parts made of cast alloys even when the castings ar made from the same heat of metal.

In order to provide improved strength in service at elevated temperatures, wrought thermal members made from the preferred high cobalt alloys described hereinbefore are subjected to a heat treatment before use at elevated temperature service. The heat treatment may comprise a double heating including a high heating at about 2000 F. to about 2400 F. for at least about hour up to about 4 hours, e.g., about 1 hour, followed by a reheating at a lower temperature of about 1500 F. to about 1800 F. for at least about A hour to about 48 hours, e.g., about 4 hours to about 24 hours. It has been found that certain alloys develop optimum properties after a triple heating in which each successive heating -is conducted at a lower temperature. Such a heat treatment comprises a high heating under the same conditions as for thedouble heating treatment and preferably about 2150 F. to about 2300 F. for about /1'120 about 4 hours, followed by a reheating at about 1700" F. to about 2100 F. for about /2 to 8 hours, e.g., about one hour, and a reheating at about 1500 F. to about 1800 P. such as that described for the double heating treatment. furnace cooling of about F. after the fir'stheating operation may be employed if desired. A feature of the very high strength alloys containing the aforementioned special amounts of cobalt is that these alloys cannot be softened to any substantial extent by heating to a'high temperature followed by a rapid cooling. The preferred high cobalt alloys provide a high combination of properties at all temperatures of interest in the heat engine art. These alloys when suitably heat treated have good notch strength and resist the undesired germination of grains which sometimes occurs in other alloys subjected to critical straining at elevated temperatures.

The heat treated preferred high cobalt alloys described hereinbefore provide outstanding properties and an outstanding service life when employed in the found highly stressed thermal members. at high temperatures,

and then extruded and hot rolled rods. The 1 about 222S F. for

given a heat treat- Heat dance with jected to the. rupture test TABLE II solidification, the ingot was heated rolled to five-eighths inch diameter ingot was heated to a temperature the extrusion and hot rolling operations. Samples were cut from the hot rolled rods and then ment before beingsub treatments which have been employed in accor the present inventionare set forth in the following table 2' to 35% will have a rupture life of hen tested at 1600 F. under i. Heat treated alloys will ife of at least about 600 hours, and often at least about 1000 hours or even 1500 hours or more,

ition to a rupf about 30,000 p.s.i. at 1500 F. igh cobalt alloy is found to develop high jected, in the form of Wrought turbine blades, to a heat treatnly the lower temperature reheating cted in the heat treated cond 7 range of about 23% at least about 200 hours w a st ress of about have a rupture 1 when subje ture test at a stress 0 The preferred h rupture strength when s thermal members, e.g., ment comp .1 tfd S S 00679933612400738170037 09906 291 C C 0 0 0 0. m 0 a e Mm mm WWWwW.M%QMMM%B%M%M%%H%%MM%%U%W$%%% r r. 0 G QO MQGG C A A W QG e mmm M g A ha A11 Lim w th m m an m as h qs s mjffi m Jsss m m mssqi s L r SS rh s sl rrrh h h rrSsr t d m mm a na a na mm 3m 1 ea 7 11 41 11 44 1 421 1 1 I. 12 1 T. C i t T... C Ah m i a. 2 .F a. a. a. :3. I. f in a s m m GABBSCFEFSIIJIJCLMNUYWNOPLLA .L FFF FFF FF FFFF FFFFF F F FFFFF t m e .5 D T ooufiooo oooono Ooouoo o0o0ooooo ua m mmm mnm mmhwmm m mmw m h mmmm d e em 0 I I I I 000 5fl5 59 5 03 5m660 0 0 m5305 r W I 0 5.. n LLQ 1 1 1 1 y 1 1 1 1 1 2 2 2 LLLLL s 0 l 2 I I I I I n c m m d a a 5 C O H n m a T H a M u u u u U n n C e .1 m 8 I n n n U "R C M m .h E N a .0 n P a n I II A l de 0 l 1 A i a E I 6 M i n n v t t m B 1 m mu m m amt h s I II hh h l t e a t. a that i a a m m I :2. m .F m em m m y I III FFF FFFF F F edufl m m I "I: 0 d u coo con 0 0 00000 B th 0 M. ufluu m @0050. u W mse c I III 333 33 3 3 2 0 S t 22 2% 22222 m n mm I flw a m t S T n u u n n II I 03 s st 1 I III 1 m m w m I umo ut I III rm W T C C o ."I" I a I I II Mm au m "III I m Mn m I IIIII F O u one on 1 X rmm r Laaataazaawnmmnmmwwwmahwammhuhaah 0 5 0 5 0 5 0 5 0 2 3 4 4 5 5 0 6 7 e LLLLLLLLLLLLLLLLLLLLLlllLlLlllLLlLl dfidn m d O 6 e t 5 t n C .tl aa383a303BBaaaaaaaflaaaaflaflaaflz aafia n t muuevamn em m am BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBR .m. m m n i inm r 1 n u o e r r a w n is a ay Xaabag mmm m ma .1 v .8 l n 0 e a a 1 t. no.5a 1 1 t e a a S 6 MW. 12270 12619131050220012101016022201 mnmm m h 1 0 W d m muh .1 A a 6 m l e 111 11110101.111 1 1101111111 1100]111.1 3A00 u k g O h n .T- n t d m t t e e w 0 0 .0 o0 0 O 0 0 0 0 0 0 0 0 n 0u00 0 uo000000000000 n m m nw t a mm e m m n t H C oflu e m n n h n N m m. a .1 f n u t m d S t O e hmmu hhwhm omwwh nwwhmnhh ha whmh w mu .4 m m mmdbn mm m m mew y R 0 0.00 .00 .000 .0 .00 .0 Mme m YZ O 8 h t 0.1.1.1 6 C 11 0 0000000000000000 .0000000000N0000000 0 C Au 8 .1 e n n n 011 mw r e m fi m cefl m a ttw s t C i on E 3X 3 H c t a a p awmmwhhmwmhmhwmmwmyhanwhuman. when m n o m m n 7 0 t w a t .1 1m 1% n H T 2 2215222222322232223222222223222222 mmm m. m wm m m m o u z d 0 w w .1 ha a r. t 1 8d 6 n t. I t. I d .1 n n t O C 0h 6 6 d 8747571.00430004599127912934777552559 MMHQ m o a C H.S Ub v. H T. t a f f n S e E 887977 9147807709398078093831002. 089 m 2L e a a 0 3 a t y W t m e .m m m mA 22 22a2232222223122azaleas 32232233322 mw 0 m cm W i wfm m P n M td wfi m fhs e fi e n m A 847 616430910322339443 154324029 .m m w e m n m W Cm w w I m m 0 P T m 009 00900160091109.1158649 001006097 ml 0 e m C a.m 0. 3 Oh U n H I 5 un mm m m h wm R ew w e e b 6 h a a e O .1 1 V. d a l r 0 t f a a m 46853420038 7057657306 255063033815 mm T WM 0 g e e.w m n .d H W a d m o .1 m1 n assas .ass J i aan n rnvm e n wu c o m e o e t 1 m e a PWC 888988988012700008 0RWOUQWSRFQQQWQWSQQQQQA OZO 1 5 .m n a W C e U W I h 6 u 6 0.0 m gt 2 222222 23222222233222222223222323 0.mw m u S. C m y unou t Wh 0 m n 8V. .8 r. t e 5h n M mu a 213294 6705580117.1202242609952873701 Nm hm m CH kT m 010. e S O t W e H mm Wvw mw 98877098918900006072992138552727894 V.1 um m 8 m e V d mot mu d H mm t a t 0C d hm c Pm m n wmwnnwmnmmmunmmwru mmmmwm t mm .w a m an w am e .1 o d whn ew a my wwdefl fl em w m m I III rmm mm m r am nnmmm n. t III r mom v m d s dae an m w I III m awmm nfla mm u e meflh s Wv n I III Nrmed pN .Ibmb e .m ddd n 0 cm A 012345 O d O eo h .mdDnSeV d t. 1 333333 beta 0 cfcbtofilmsaaaafarm bath was then poured into a cast iron mold. After TABLE IV' [Test Conditions-l600 F. and 30,000 p.s.L]

Alloy No. Heat 'lreat- Rupture ment Life, Hours A 135 A 137 A 125 A 96 'In order to demonstrate the. high order of stress rupture properties developed by the preferred cobalt-containing alloys contemplated in accordancewith the invention at temperatures of 1500 F., 1600 F., 1700" -F., and 1800" F., the following table sets forth the results of stress rupture tests conducted upon Alloy-18 at these temperatures. The test specimens were prepared from hot rolled bar stock and were subjected to a heat treatment comprising heating to about 2275 F., furnace cooling 100 F., air cooling, heating to about 2000 F. for about 1 hour, air cooling, heating to about 1600 F. for about 4 hours and air cooling.

TABLE V Stress Rupture Test Conditions Life, Hrs. Elongation,

Percent Temp, F. Stress, p.s.l.

62 as 40, 0 1 L500 so. 000 1, 085 10 25, 000 1, 587 5 40. 008 6g 30. 00 L600 25. 000 280 15 20,000 748 14 25, 000 8 22 20, 000 38 30 1,700 15. 000 113 13. 5 l 12, 000 184 7, 5 8. 000 1, 048 2. 5 10, 000 l1 1,800 S, 000 36. 5 52 5' A further series of stress rupture tests were conducted upon hot rolled bar stock from Alloy 18 whichhad been heat treated at 2150" F. for 2 hours, air cooled, and then heated 1600 F. for about 4 hours. This heat treatment is designed to provide a finer grain size with high properties. The data are presented in the following table:

A series of stress rupture'tests was conducted upon-Al loy 35 to demonstrate the effects of heat treatment upon the rupture life of the alloy at 1600 F. and 28,000 p.s.i. The heat treatments and the accompanying rupture lives 5 under the foregoing conditions are given in the following Table VII:

TABLE VII High Heating Temperature, Reheatiug Rupture Elongation, "F.(2-hourtreatrnent),A.C. Conditions, Life, Hours Percent F./hrs.

It was observed that the alloys sub ected to the foregoing tests were also hlghly resistant to creep, another factor which is very important in evaluating metals for use in thermal members which are subjected to high temperatures and high stresses in service. In addition, the heat treated wrought alloys are characterized by-a high strength and adequate ductility at ordinary temperatures as evidenced by a yield strength of at least about 100,000

p.s.i., a tensile strength of at least about 160,000 p.s.i. and an elongation of at least about 20% in 2 inches when measured at atmospheric temperatures.

As previously noted, preferred cobalt-containing cast 5 alloys within the present invention provide high properties at elevated temperatures. The compositions of satisfactory cast alloys are given in the following table:

TABLE VIII 'Per- Per- Per- Per- Per- Per- Per- Alloy No. cent cent cent cent cent cent cent Cr Co Mo Al Ti 0' Ni 28. 7 3.20 3 26 2. 22 0.15 Bal. 28.0 3.28 3 78 2. .53 0.18 E21. 28 3. 40 4. 36 2. 83 0. l8 Bal. 28 1.20 8, 22 2.02 0. 13 B211.

1 Including small amounts of boron and zirc anium resulting from the additions of about 0.003 2; and about 0.05% of these elements, respectively.

The properties of the foregoing cast alloys tested in the as-cast condition and at 1600 F. and 30,000 p.s.i. ar e as follows:

timum strength at elevated temperatures.

1 T.S., p.s.i.=Tensile Strength in pounds per square inch. 2 EL, Percent=Elongation in percent.

Low cobalt alloys It has also been discovered that certain alloys free of columbium and tungsten and containing relatively low amounts of cobalt comprehended in the scope of the present invention will provide very satisfactory heat and stress resisting thermal members and possess commercial malleability. These alloys possess advantages in that the highly strategic elements columbium and tungsten are unnecessary for their production and no cobalt or only small amounts of cobalt, which is itself a strategic element, are required. Such alloys comprise about 0.05% to about 0.35% carbon, about 5% to 17% chromium, up to about cobalt, about 1% to 10% molybdenum,

about 3.5% to 8.5% of aluminum plus titanium with the ratio of aluminum to titanium being about 0L5z11up to about 3:1. These alloys desirably contain boron and zirconium in very small amounts in order to provide op- It is to be understood that these alloys likewise are malleable in the absence of either or both of boron and zirconium. When boron is present, it is employed in quantities of a few tenthousandths of one per cent, e.g., about 0.0002% or 0.0003% up to about 0.009%, preferably 0.000s% to 0.009%, e.g., 0.0007% to 0.007%.

Zirconium, when used, may be present in amounts of about 0.01% to about 0.25%, e.g., about 0.03% to about 0.08%.

I Special wrought alloys having relatively low cobaltcontents include those set forth in the following schedule:

Improved high temperature properties are developed in the foregoing low cobalt alloys, including cobalt-free alloys, when boron and zirconium are present in very small amounts Within the ranges set forth hereinbefore.

It is to be understood that the alloys of column A in the foregoing schedule are preferred inapplications where ductility at service temperatures intherange of about 1200 F. to about 1600" F. is of prime importance, e.g., rotor wheels. When high strength at the service temperature range of about 500 F. to about 1800 F. is required, as in turbine blades, then the alloys defined in column B of the foregoing schedule are desirable.

For optimum strength, including high rupture life at the service temperature range of about 1500 F. to about 1800 F., the alloys of column C in the foregoing schedule are preferred. When high notch strength at service temperatures in the range of about 1200 F. to about 1500 F. is of prime importance, the alloys of column D in the foregoing schedule are preferred.

' amazes The copresence of molybdenum, boron, carbon and zirconium in combination with chromium, aluminum and -titanium in thespecial proportions indicated hereinbefore for the special low-cobalt alloys contemplated in accordance with the present invention enables the production i of wrought nickel alloys having high rupture life of the same or higher order than other wrought alloys containf ing the strategic elements columbium and tungsten and/or containing larger amounts of cobalt.

The presence of chromium in the aforementioned ranges is important and the presence of chromium in combination with the other elements imparts oxidation resistance to the alloy and is also important as a matrix stiffening or hardening element. Aluminum and titanium are important harden- .ing and stiffeningelements. Aluminum is also advantageous in imparting oxidation resistance to the alloy. Carbon is important in combination with the other ingredients of the low cobalt compositions as setforth hereinbefore. Carbon preferably is present in amounts of about 0.08% to about 0.18% in order to assist in maintaining fine grain size and to impart improved rupture strength at elevated temperatures. The presence of molybdenum in the alloy is particularly effective in combination with the amounts of the other elements of the low cobalt compositions set forth hereinbefore', especially in enabling the production of alloys having good high temperature properties and the molybdenum preferably is present in amounts of about 2% to about 4%. Iron is an optional element and may be present in amounts up to about 5%.

Molybdenum, like chromium, has a matrix stiffening or hardening effect on all the alloys described here in and is about twice as effective as chromium as a matrix hardener. In the special low-cobalt alloys defined in columns B and C of Table X, it is more pre- 'ferred when the aluminum plus titanium content is at a high combination of properties at elevated temperatures.

It is also to be understood that the low cobalt alloys defined hereinbefore are malleable and may be worked into thermal members such as blades for aircraft turbojet engines andthe like. The alloys may also be fabricated as castings for use as thermal members. In cases where it is desired to employ the alloy in the form of cast thermal members, the boron content may be increased to as high as about 0.02% and the carbon content may be increased to as high as about 0.5%. As noted hereinbefore, it is generally thought that cast thermal members are not as consistent in properties from piece to 'piece as is the case when the thermal members are worked to shape as by forging, hot rolling, extrusion, etc.

It is to be understood that the aforementioned wrought low cobalt alloys develop their best properties at high temperatures when subjected to a heat treatment such as the double heating treatment or the triple heating treatment described hereinbefore for the wrought high cobalt alloys. Like the cobalt-containing alloys described hereinbefore, the preferred low cobalt alloys comprehended in accordance with the present invention are characterized by the fact that they cannot be sub- ..is presented:

about 20 hours at about 1300 F.

TABLE XI Per- Per- Per- Per- Per- Per- Per- Per- Per- Alloy No. cont cent cent cent cent cent cent cent cent Cr Fe Al Ti 'Mo 0 Zr N U 10. 59 0. 23 2. 93 1. 84 3. '11 0. 06 0. 072 Ba]. 11 58 0. 32 2. 51 2. 62 2. 36 0. 06 0. 053 B111. 10. 77 0. l3 2. 73 1. 80 3. 06 0. 06 0. 057 Bal. 10.85 3 64 2. 84 1.83 2. 94 0. 05 0.056 Ba]. 10. 62 3. 95 2. 73 1. 65 2. 95 0. 06 0.061 B211. 10. 25 0. 2. 91 2. 51 2. 95 0.07 0. 057 Bal. 10. 92 1. 53 3-0 3.0 3. 03 0.08 0.041 'Bal. 8. 16 1. 83 3. 8 2. 7 3. 12 0. 0S 0. 041 Bal. 10.33 0.18 3. 43 2. 40 3 03 0. 08 0.018 Bal. 8. 31 0. 18 3. 63 2. 67 3. 00.. 0. 09, 0. 055 Bai. 7. 91 0. 40 3. 64 2. 70 3. 92 n. 00 0.062 Bal. 7.80 0. 14 3. 32 2. 46 4. 86 0. l0 0. 050 Bal. 10. 16 4. 76 0. 18 3. 13 2. 22 3. 03 0. 08: 0. 053 Hal. 9. 51 4. 73 0. 3. 60 2. 66 3. 02 0. 00 0. 062 Bal. 8. -6 5. 04 0. 16 3 56 2. d7 3. 04 0. 10 0.052 32.1. 14. 73 4. 78 0. 17 2. 83 1. 77 3. 02 0.08 0.052 Bal. 10.16 0. 16 2. 3. 20 2. 86 0. 06 0.051 Bal. 11. 09 8. 10 0. 16 3.0 2. 5 3. 07 0.08 0. 048. Bal. 8. 4-1 4. 83 0. 20 3. 59 2. 67 2. 93 0.08 0.057 Ba]. 11. 56 8. 16 0. l6 8. 3 2.0 3.05 0. 07 O. 041 Bal. 11. 13 7. 73 0. 19 3. 0 2. 4 2. 96 0.09 0. 046 Ba]. 8. 30 4. 84 0.30 3.71 2. 74 3. 01 0. 09 0.055 Bal. 11.87 0.15 2. 86 2. 53 2. 95 0. l0 0 041 Bal. 8.11 5. 43 1.03 3. 8 2. 7 2. 89 0.09 0 041 Bal. 10.39 0. 19 3. 16 2. 26 2. 95 0. 07 0. 052 Be]. 9. 75 1.01 0. 41 3. 46 2. 57 2. 85 0. 09' 0. 053 Bal. 11. 86 4. 94 0. 16 3.02 2. 3.03 0. 08' 0. 046 B21. 14. 27 4. 96 0. 30 3. 16 2. 25 3.03 0.08 0. 041 Bal.

Norm-Alloys to 44 contained about 0.002%, 0.007%, 0.007%, 0.007%, and 0.003% boron. respectively. Alloys to 52, 55 to 59, 61 to 6 66 and 67 contained boron resulting from an addition of about 0.003% boronto the respective melts and Alloys 53, 54. 60 and 65 contained boron resulting from an addition of about 0.005% boron to the respective melts.

1 Balance includes small amounts oi manganese, magnesium, silicon, coppenetc.

The rupture life of heat treated alloys 40 through 44 TABLE XIV at 1500 F. and a load of 30,000 p'.'s.i. is given in the [Test Conditions-1350" F. and 70.000 p.s.i.]

Heated for about 4 hours at about 2100 F., air cooled, and heated heated at lfiooo [or about 4 hours about 20 hours at about 1300 F., air cooled. I V 2 Heated for about 8 hours at about 1975 F., air cooled, and heated 7 TABLE xv [Test Conditions-1800" F. and 8,000 p.s.i.]

following table: I g

' TABLE XII Alloy N Heat Treat Rupture Life, Elongation,

rnent, F. hours percent Alloy N0. Rupture Life, Rupture Life, 40 45 i 2 57 7 5 1 Alloys heated 2 hours at temperature noted, air cooled, and then r The rupture lives of other alloys after the indicated-- heat treatments and under the indicatedconditions are" ,Almy g g f gf g shown in the following tables:

L 103 TABLE XIII 50: B-. iii [Test Conditions-1600? F. and 25,000 p.s.i.] ii 5s 2,325 10s Alloy N o. Heat Treat- Rupture Life, 7 67 142 ment hours H 1 Alloys heat treated 2 hours at the indicated temperature, air cooled 45- .L '5 and then heated for about 4 hours at 1600 F. 46 X .163 g g: In manufacturing the foregoing alloys, nickel and .49. L--. 240 chromium were melted in an induction furnace and the 29- -3 molybdenumwas then incorporated in the melt. Carbon was then added in'the form of a master alloy contain- 379 ing about 10% carbon and 90% chromium. Thereafter, 2? 1 8 about one-half of the aluminum was added, followed by an addition of magnesium and zirconium. The balance g of the aluminum was added next, followed by the intrm duction of the titanium and finally the boron. Usually, the zirconium and boron, and sometimes the magnesium 'j V239 and titanium, are'added as master alloys. With respect 66. CW 172 totitanium, it. is preferred to add the titanium in the purest elemental, form available. The molten bath was then poured into a cast iron mold. After solidification, the ingot was heated and then forged and rolled to fiveeighths inch diameter hot rolled rods. The ingot was heated to a temperature of about 2225 F. for theforging and hot rolling operations.

Low chromium, high cobalt alloys It has been found in applications involving exposure of wrought thermal members to very high service temperatures on the order of about 1700 F. or higher, and involving the requirement for a high order of commercial forgeability, that special alloys within the inven-.

'16 scribed low chromium, high cobalt alloys preferably are subjected to a heattreatment before being employed in service. Either the double heating treatment or the triple heating treatment described hereinbefore in conjunction 'with other high cobalt alloys within the scope of the invention may be employed in treating the low chromium, high cobalt alloys. These alloys in the heat treated condition will have a rupture life of at least about 100 hours, and usually about 200 hours or more, when tested at about 1600 F. and 25,000 psi. The following table contains the analyses of satisfactory low chromium, high cobalt alloys produced in accordance with the invention:

TABLE A Alloy No.

Per Percent Percent Per Per- Percent cent Percent Per- Percent cent Cr Co Mo Al Ti Zr B l Ni 1 Amounts added to melt. Balance includes small amounts of manganese, magnesium, iron, silicon, copper, etc.

tion are particularly suitable. These alloys contain about 7% to 9% or 11% chromium, at least about 8%, e.'g., about up to about 30%, cobalt, about 5% to 8.5%

of aluminum plus titanium with the ratio of aluminum to titanium being within the range of about 0.5 to l and about 3 to 1, about 1% to 10% molybdenum, up to about 1 5% iron, and the balance essentially nickel. Preferably,

such alloys contain about 2% to 6% molybdenum and having a ratio of aluminum to titanium which is between about 0.8 to 1 and about 1.6 to 1.

In order to provide optimum strength at service temperatures of about 1700 F. or higher, it is preferable that these alloys contain small amounts of boron and zirconium within the range of about 0.0002% to 0.009% boron and about 0.01% to about 0.25% zirconium. Preferably, the alloys'will contain about 0.0004% to Machined rupture test specimens cut from hot rolled rods made from the foregoing alloys were heat treated and subjected to stress rupture tests at 1600 F. and 25,000 p.s.i. The results of the stress rupture tests are) presented in the following table:

TABLE B Alloy N 0. Heat Treat- Rupture mcnt Life, hours Q 205 A 251 B 201 Alloy No. 70, when given Heat Treatment B and subjected to a stress rupture test at 1800 F. and 8,000

0.007% boron and .01% to 0.15% z1rcon1um or, more 4 p.s.1., exhtbrted a rupture life of 141 hours. preferably, about 0.0005% to 0.005% boron and about The following table sets forth the compositions of 0.03% to about 0.08% z1rc0n1um. other alloys contemplated 1n accordance w1th the present Wrought thermal members made from the'aforedeinvention:

3 TABLE XVI Pl.-1- Per- Por- Pvr- Por- Pcr- Per- 4 Per- Per- Per- Alloy N 0. cent PPM. cent cent cent cent cent cent cent cent Cr Co Fe Al Ti M0 0 Zr N l l 0. 34 2 3s 1. 55 3.15 0. 0s 0. 040 0.00 B01. 002 233 1.53 2.31 0.07 0. 0 5 00 15 33.1. 0 21 2.23 1 02 3v 17 0. 07 0. 005 0005 B31.

70 2.34 1.0 3 01 0. 00 0.053 001-15 1331 3.73 2. 30 1 2. 33 0. 05 0.053 0.001 Bal 0.10 2.35 1 51 1.10 0. 07 0. 000 0 003 1741 0.15 2. 35 1 53 1.00 0 00 0.057 0003 B31 0.13 2.40 1 47 3. 00 0.01 0.053 0, 003 Del. 0.10 2. 34 1 52 3.04 0 10 0.002 0 003 0 2. s4 1 15 2 00 0. 0s 0. 034 0.003 B3]. 0.15 2 47 1 44 4.04 0 00 0. 05s 0 005 Bal 0.25 1.30 2 70 3.17 0.05 0 043 0.003 1301 4.75 2. 33 1 72 3. 04 0.03 0.053 0. 003 1331 0 22 2 1 00 3.04 0. 0s 0 072 0 003 Be] 0. 30 2. 30 1. 59 3. 12 0. 07 0 055 0 003 1321 0. 21 2.09 1 00 2. s2 0. 7 0.072 0 003 B31 4 30 2. 42 1.51 3. 03 0. 0e 0. 053 0 007 B01 3. 02 2. 20 1,50 2 03 0. 00 0. 0 .0 0 005 1331 3.70 2. 43 1 50 3.31 0. 07 0. 04 0 003 B31 3. 71 2.10 1 4 71 0.00 0. 045 0 007 Bal 0.12 2.00 1. 32 2. 04 0.00 0. 05s 0 003 E01 0.13 3.41 2.00 3. 03 0. 00 0. 055 0 005 1351 0. 23 2. 73 1. 3t 7. 3r 0. 00 0 105 0 00: B01 10. 40 0.35 2.39 1.51 2. 35 0.11 0.030 0 003 B01 19.42 0.17 2.37 1. 3 03 0. 0s 0. 055 0 003 B21 10 00 0.30 2. 34 1.54 3.07 0.11 0.002 0 003 R111 18.32 0.30 2.33 1. is 2.38 0.10 0. )5 0 0021 B31 12. 00 0.22 1.32 2.53 3.34 0.05 0. 57 0 005 Be! 773 0.31 2.53 1. 00 3.02 0. 0." 0. 052 0 003 E01 7.20 0.77 2. 73 1.01 2 s9 0 5 0 05 0 002 1321 3.00 3. 00 2.33 1.00 3 10 0.07 0. 053 0 003 1011 10. 00 0. 20 2.53 1 3.04 0 07 0 .0 0 005 1301 10. 21 0.11 2. s5 0. 00 3.09 0. 07 0 2 0,004 133.1 9.74 0. 21 2.57 2. 05 3.15 0.07 0 052 0.003 1431 0.14 .233 1. 45 1.10 0.07 0.002 0.003 Hal 0 30 2. 20. 1. 50 2 02 0.10 0. 053 0.003 B31 0. 44 2.35 1.70 2. 05 0.11 0. 053 0. 003 E01. 1.14 1.17 2 57 3.01 0.04 0.052 0.003 1321.

Balance includes small amounts of manganese. magnesium, silicon, copper, etc.

The rupture lives of the foregoing alloys, as determined at 1500 F. and' 30,000 p.s.i; after a heat treatment as noted, are given in the following table:

TABLE XVII RupturcLiie, Hours Alloy No.

Heat Treat- Heat Treatment No. 1 ment No. 2

1. Heated for about 4 hours at about 2100 F., air cooled, and heated [or about 2) hours at about 1300 F., air cooled.

2. Heaiel for about 8 hours at about 1975 F., air cooled, and heated about 20 hours at about 1300 F.

TABLE XVIII Per- Per,-. Per- Per- Per- Pcr- Per- Per- Alloy No. cent cent cent cent cent cent cent cent Co Mo r Al Ti B Zr Specimens made from the foregoing alloys were heat treated and subjected to stress rupture tests at 1700 F. and 20,000 p.s.i., with the following results:

TABLE XIX Rupture Life, Hours Heat Treating Temperature, F. Alloy Alloy Alloy Alloy Alloy Alloy 109 110 111 112 113 114 o 1 Specimens held for about 2 hours at temperature noted, air cooled and reheated at about 1600 F. for about 24 hours.

Two other series of'tes'ts were conducted'to illustrate the effects of the zirconium-boron treatment upon the rupture life' of forged and rolled alloys with the following results:

. TABLE XX Per- Per- Per- Per- Per- Per- Per- Per- Rup- Alloy N 0. cent cent cent cent cent cent cent cent ture 00 Mo Or Al Ti 0 B Zr Life,

Hrs.

30 3 15 3. 0 2. 3 0. 10 n.a n.a. 100. 5 30 3 15 3.0 2. 3 0.10 n.a. 205 30 3 15 3. 0 2. 3 0. 10 367 30 3 15 3. 0 2. 8 0. 10 no. 301 30 3 15 3. 0 2. 8 0. 10 626 1 Contains boron resulting from addition of 0.003% and/or contains zirconium resultin g from addition 010.05%.

2 Test conditions: 1600 F. and 25,000 p.s.i. stress. n.a.=none added. I

The foregoing alloys were subjected to heat treatments as 5 follows:

TABLE XXI Alloy N o. Initial Heating Reheating 2,325 Fig-2 hrs.,A. C 2,325" F.-1 hr.-, A.C

It is to be noted from the foregoing tabulation that the incorporation of special amounts of either, and particularly both, of the elements boron and zirconium in alloys contemplated by the present invention contributes to the high temperature strength properties achieved therein.

Alloys produced in accordance with the invention are resistant to germination or abnormal grain growth when subjected to elevated temperatures after straining. The alloys are also highly resistant to oxidation, a desirable characteristic in gas turbine blade applications. The alloys are also adaptable to production in wrought form such as bars, rods, billets and the like, starting with a big ingot casting. Many prior alloys have not been susceptible to mill processing starting with a big ingot and this lack has been undesirable from a number of standpoints, including higher cost of other processing methods, lack of uniformity in properties and structures from piece to piece, etc.

A preferred method for the mill processing of alloys contemplated in accordance with the invention comprises preparing a melt of the particular alloy in an induction furnace which may or may not be provided with a vacuum or other special atmosphere, casting the alloy into ingots'approximately 9 inches in diameter and about 28 inches long, heating the ingots to a temperature in the range of about 2000" F. to about 2100 F., extruding the ingots with a glass lubricant to provide billets having a cross section of about 4 square inches to about 9 square inches, and thereafter hot rolling the billets thus prepared. It is preferred that the subsequent hot working, e.g., hot rolling, be accomplished within the temperature range of about 1900 F. to about 2225 F.

It has been found that the present nickel-chromium alloys possess both hot workability and cold workability and can be produced on an industrial scale into products acceptable to the trade. For instance, when nickelchromium alloys, such as are illustrated hereinbefore, are made it has been found that they can be fabricated in modern machinery, such as by modern high-powered forging, rolling, drawing, upsetting, extrusion, machining, grinding, etc. The alloys of the present invention can also be employed in the cast form, e.g., as precision castings.

The present invention provides a special nickel-chromium alloy which is particularly applicable to the manufacture of and use as thermal members. The term thermal members as employed herein is intended to include structural members which in use are subjected to heat and stress at elevated temperatures, particularly such structural members of heat engines, such as jet engines, gas turbines, turbo-superchargers, exhaust-gas power recovery turbines, etc., by which heat is transformed into mechanical work. Illustrative examples of some of the thermal members contemplated by the invention include turbine blades such as rotor blades or buckets and stator blades or nozzle guide vanes, rotor wheels, structural rings for gas turbine assembly, etc.; valves, valve seats and accessories, exhaust manifolds and supports therefor, etc.; combustion liners or flame tubes, tail cones, after-burner parts, vaporizer tubes and other high temperature tubular members, high temperature gas seals, etc.; high temperature springs and other resilient members; high temperature bolts, studs, fasteners, nuts, etc.;

high temperature stiffening and supporting members; etc.

The present applicationris a continuation-in-part of my co-pending applications Serial No. 250,161 and Serial No. 250,162, both filed October 6, 1951 and both now abandoned.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the artwill readily,un-

derstand. Such modifications and variations are considered to be within the purview and scope of the inven tion and appended claims.

I claim:

1. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for' extended periods of time under conditions of high stress and elevated temperature which comprises about 14%- to 17% chromium, about 2% to 4% molybdenum, about 23% to 35% cobalt, about 0.1 to 0.25% carbon, about 5% to 7% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 0.8 to 1 up to about 1.6 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.15% zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by'a rupture life of at least about 200 hours at 1600 F. and 25,000 pounds per'square inch.

2. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 12% to 18% chromium, about 1% to 10% molybdenum, about 20% to 40% cobalt, about 0.05 to 0.35% carbon, about 4.8% to 8.5% of aluminum plus titanium with the ratio of aluminum to-titanium being in the range of about 0.5 to 1 up to about 3 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.25 zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of at least about 200 hours at 1600 F. and 25,000 pounds per square inch.

3. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods .of time under conditions of high stress and elevated temperature which comprises about 5% to 20% chromium, about 1% to 10% molybdenum, about from about 0.01% to about 0.25% zirconium, and with the balance essentially nickel, said alloy being ch-arac-- terized in the heat treated condition by a rupture life of at least about hours when tested at 1600 F. and

25,000 pounds per square inch.

4. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 5% to 9% chromium, about 1% to 10% molybdenum, not more than about 10% cobalt, about 0.05 to 0.35% carbon, about 5.5% to 8.5% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 0.5 to 1 up to about 3 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.25% zirconium, and with the balance essentially nickel, said alloy being characterized by a high level of rupture strength in the temperature range of 1700 to 1800 F.

5. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 7% to 11% chromium, about 2% to 4% molybednum, up to about 8% cobalt, about 0.05% to 0.25% carbon, about 5.5% to 7% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 3 to 2 up to about 1 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.25% zirconium, and with the balance essentially nickel, said alloy being readily wrought and ei ng characterized by a high combinationof properties atelevated temperature.

A hot-workable, coldworkable, heat-resistant ,alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress :and elevated temperature which comprises about 10% to 15% chromium, about 2% to 4% molybdenum, about 3% to 8% cobalt, about 0.05 to 0.25% carbon, about 4.5 to 6% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 3 to 2 up to about 1 to 1, not morethan about iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.25% zirconium, and with the balance essentially nickel, said alloy having a high notch strength at service temperatures of 'abouti120 0 to l500 7. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperaturewhich comprises about 7% to 13% chromium, about 2% to 4% molybdenum, about 3% to 8% cobalt, about 0.05% to 0.25% carbon, about 5% to 7% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 3 to 2 up to about 1 to 1, not more than about 5% iron from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.15% zirconium, and withthe balance essentially nickel, said alloy having a high rupture life in the service temperature range of about 1500 to 1800" F. p 8. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 7% to 13% chromium, about 2% to 4% molybdenum, up to about 3% cobalt, about 0.05 to 0.25 carbon, about 5% to 7% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 3 to 2 up to about 1 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.15 zirconium, and with the balance essentially nickel, said alloy having a high strength at service temperatures of about 1500 to 1800 F.

9. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 8% to 13% chromium, about 2% to 4% molybdenum, up to about 3% cobalt, about 0.05% to 0.25 carbon, about 4.5% to 6% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 3 to 2 up to about 1 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.15% zirconium, and with the balance essentially nickel, said alloy having high ductility at service temperatures of about 1200 to 1600 F.

10. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 5% to 17% chromium, about 1% to 10% molybdenum, up to about 10% cobalt, about 0.05 to 0.35% carbon, about 4.5% to 8.5% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 0.51 to 1 up to about 3 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.25% zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of at least about 100 hours when tested at 1600 F. and 25,000 pounds per square inch.

11. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 7% to 11% chromium, about 2% to 6% molybdenum, about 10% to 30% cobalt, about 0.05% to 0.35% carbon,

- -22 abqntfi /t t 7 5% ofa u n a tn luetitaa m w th the ratio of aluminum to titanium being the range of about 0.8 to 1 up to about 1.6.t0 1, .not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.25% zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of at least about 100 hours when tested at 1600 F. and 25,000 pounds per square inch. I I Y 12. hot-workable, cold yvorkable, heat-resistant a1- loy particularly adapted to service as a thermal member for extended periods. of time under conditions of high e s nd..,1evat.d temp ra which comp about 7% to I1 chromium,.about 1% to 10% molybdenum,

at least abput. 8% and .upto about cobalt, about 0.05% to 0.35% carbon, about 5% to 8.5 of aluminum plus titanium with the ratio, oi aluminum to titanium being in. therange of about 0.5 to 1 .up to about 3 to 1, not e th a out 5% r rfrem P t -0 to about 0.009% boron, from about 0.01% to about 0.25 zirconium, andwith the balance essentially nickel, said alloy being charaeterized in the heat treated condition by a rupture life of at least about 100 hours when tested at 1600 F. and 25,000 pounds per square inch.

'13. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as. a thermal member for extended periods of time under conditions of high stress -and elevated temperature which comprises about 5% to 20% chromium, about 1% to 10% molybdenum, up to about 40% cobalt, about 0.05% to 0.35% carbon, about 4.5% to 6% of aluminum plus titanium with the ratio of aluminum totitaniurn being in the range of about 0.8 to 1 up to about 1.6 to 1, not more than about 5% iron, from about 0.0002%.to about 0.009% boron, from about 0.01% to about 0.25 zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of at least about hours when tested at 1600 F. and 25,000 pounds per square inch,

14. A hot-workable, cold-workable, heat-resistant alalloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 5% to 20% chromium, about 1% to 10% molybdenum, up to about 40% cobalt, about 0.05% to 0.35% carbon, about 5% to 7% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 0.8 to 1 up to about 1.6 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.25% zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of at least about 100 hours when tested at 1600 F. and 25,000 pounds per square inch.

15. A hot-workable, cold-workable, heat-resistant alloy particularly adapted to service as a thermal member for extended periods of time under conditions of high stress and elevated temperature which comprises about 5% to 20% chromium, about 1% to 10% molybdenum, up to about 40% cobalt, about 0.05% to 0.35 carbon, about 4.5% to 8.5 of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 0.5 to 1 up to about 3 to 1, not more than about 5% iron, from about 0.0002% to about 0.009% boron, from about 0.01% to about 0.25% zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of at least about 100 hours when tested at 1600 F. and 25,000 pounds per square inch. V

16. A thermal member particularly adapted to service for extended periods of time under conditions of high stress and elevated temperature which comprises about 5% to 20% chromium, about 1% to 10% molybdenum, up to about 40% cobalt, about 0.05 to 0.5% carbon, about 4.5% to 8.5% of aluminum plus titanium with the ratio of aluminum to titanium being in the range of about 0.5 to 1 up to about 3 to 1, not more than about 5% iron, from about 0.0002% to about 0.02% boron, from about 0.01% to about 0.25 zirconium, and with the balance essentially nickel, said thermal member being characterized in the heat treated condition by a rupture life of at least about 100 hours when tested at 1600 F. and 25,000 pounds per square inch.

17. The method for improving'the stress rupture properties of thermal members for service at high stress levels for extended periods of time which comprises establishing a molten bath of an alloy containing about 5% to 20% chromium, about 1% to 10% molybdenum, up to about 40% cobalt, up to about.5% iron, about 4.5% to about 8.5% of aluminum plus .titanium with the ratio of aluminum to titanium being in the range of about 0.5 to 1 up to aobut 3 to l and with the balance essentially nickel and introducing into said bath shortly before casting boron and zirconium in amounts sutficient to provide respective contents thereof of about 0.0002% to 0.009% and 0.01% to 0.25% in metal cast from the thus-treated bath, casting metal from the thus-treated bath to ingot form and hot working said ingot to provide wrought thermal membls characterized in the heat treated condition by a rupture life of at least about 100 hours when tested at 1600 F. and 25,000 pounds per square inch.

18. A hot-workable, cold-workable, heat-resistant alloy particularly adapted for service for extended periods of time under conditions of high stress and elevated temperature which comprises about 11% chromium, about 3% molybdenum, about 10% cobalt, about 0.7% carbon, about 2.6% aluminum, about 2.7% titanium, about 0.2% iron, about 0.003% boron, from about 0.01% to about 0.15% zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by high rupture strength at temperatures of about 1500 F. and higher.

19. A hot-workable, cold-workable, heat-resistant alloy particularly adapted for service for extended periods of time under conditions of high stress and elevated temperature which comprises about 14% chromium, about 3% molybdenum, about 28% cobalt, about 0.11% carbon, about 2.9% aluminum, about 2.7% titanium, about 0.003% boron, about 0.04% zirconium, and with the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of at least about 200 hours when tested at 1600 F. and 25,0 0 pounds per square inch.

20. A hot-workable, cold-workable, heat-resistant alloy particularly adapted for service at extended periods of time under conditions of high stress and elevated temperature which comprises about 8% chromium, about cobalt, about 0.3% iron, about 3.7% aluminum, about 2.7% titanium, about 3% molybdenum, about 0.05% zirconium, about 0.10% carbon, about 0.003% boron and the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of about 517 hours when tested at 1600 F. and 25,000 pounds per square inch.

21. A hot-workable, cold-workable, heat-resistant a1- loy particularly adapted for service at extended periods of time under conditions of high stress and elevated temperature which comprises about 8% chromium, about 13% cobalt, about 3% molybdenum, about 0.12% carbon, about 3.6% aluminum, about 2.8% titanium, about 0.05 zirconium, about 0.004% boron and the balance essentially nickel, said alloy being characterized in the heat treated condition by a rupture life of at least about 24 200 hours when tested at 1600 F. and 25,000 pounds per inch. i

22. A nickel base alloy containing about 15 percent to 20 percent chromium, about 15 percent to 30 percent cobalt, about 1.5 percent to 10 percent molybdenum, about 2.5 percent to 5.66 percent titanium, abo ut.2.75 percent to 5 percent aluminum, the alloy being capable of withstanding an applied stress of thirty-five thousand pounds per square inch at 1500 F. for a time in excess of two hundred hours continuously. .without rupture.

23. A nickel-base alloy containing from about 5% to 20% chromium, from about 1% to 10% molybdenum, from about 10% to 40% cobalt, from about 4.8% to 8.5% of aluminum plus titanium with the ratio of aluminum to titanium being from about 0.5 to l to 3 to l, the alloy being capable of withstanding an applied stress of thirty-five thousand pounds per square inch at 1500? F. for a time in excess of 200 hours continuously, without rupture.

24. A nickel-base alloy containing from about 5% to 20% chromium, from about 1% to 10% molybdenum, up to about 40% cobalt, from about 4.5% to 8.5% of aluminum plus titanium with the ratio of aluminum to titanium being from about 0.5 to l to 3 to 1, the alloy being capable of withstanding an applied stress of thirty five thousand pounds per square inch at 1500 F. for a time in excess of 200 hours continuously, without rupture.

25. Analloycontaining about 5% to 20% chromium, about 1%-to 10% molybdenum-about 10% to about 40% cobalt, about 4.8% to 8.5% of aluminum plus titanium with the ratio of aluminum to titanium being from about 0.5 to 1 to 3 to 1, about 0.05% to 0.5% carbon, not more than about 5% iron, up to about 0.02% boron, up to about 0.25% zirconium and the balance being essentially nickel, the alloy being capable of withstanding an applied stress of thirty-five thousand pounds per square inch at 1500 F. for a time in excess of 200 hours continuously, without rupture.

26. A nickel-base alloy containing from about 5% to 20% chromium, from about 1% to 10% molybdenum, up to about 40% cobalt, from about 4.5% to 8.5% of aluminum plus titanium with the ratio of aluminum to titanium being from about 0.5 to 1 to 3 to 1, about 0.0002% to 0.009% boron, up to about 0.25% zirconium, the alloy being capable of withstanding an applied stress of thirty-five thousand pounds per square inch at 1500" F. for a time in excess of 200 hours continuously, without rupture.

27. A nickel-base alloy containing about 15% to 20% chromium, about 15% to 30% cobalt, about 1.5%. to 10% molybdenum, about 2.5% to 5.66% titanium, about 2.75% to 5% aluminum, about 0.0002% to 0.009% boron, about 0.01% to 0.25% zirconium,.the alloy being capable of withstanding an applied stress of thirty-five thousand pounds per square inch at 1500 F. for a time in excess of 200 hours continuously, without rupture.

References (Iited in the file of this patent UNITED STATES PATENTS 2,150,095 Kayes Mar. 7, 1939 2,570,193 Bieber et a1 Oct. 9, 1951 2,575,915 Guy Nov. 20, 1951 2,688,536 Callaway et al. Sept. 7, 1954 2,712,498 Gresham et al. July 5, 1955 FOREIGN PATENTS 632,712 Great Britain Dec. 5, 1949 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No.,2 ,i977,222 March 28 1961 Clarence George Bieber It is Hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3,, line 42 for "tunsten" read, tungsten column l5 line 32, for "having" read have line 40, for 201% read 0., 1% column 20,, line 9, for "0. 1-" read 0. 1% line 24, for "0.05" read 0.05% same column 20, line 68, for 'molybednum": read molybdenum column 21, line 63, for "0051" read 005 column 23 line 17 .for aobut read about line 32, for "0.1%" read 0.07%

Signed and sealed this 29th day of August 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

Claims (1)

1. 24. A NICKEL-BASE ALLOY CONTAINING FROM ABOUT 5% TO 20% CHROMIUM, FROM ABOUT 1% TO 10% MOLYBDENUM, UP TO ABOUT 40% COBALT, FROM ABOUT 4.5% TO 8.5% OF ALUMINUM PLUS TITANIUM WITH THE RATIO OF ALUMINUM TO TITANIUM BEING FROM ABOUT 0.5 TO 1 TO 3 TO 1, THE ALLOY BEING CAPABLE OF WITHSTANDING AN APPLIED STRESS OF THIRTYFIVE THOUSAND POUNDS PER SQUARE INCH AT 1500* F. FOR A TIME IN EXCESS OF 200 HOURS CONTINUOUSLY, WITHOUT RUPTURE.