US2570193A

US2570193A - High-temperature alloys and articles

Info

Publication number: US2570193A
Application number: US660748A
Authority: US
Inventors: Bieber Clarence George; Sumpter Walter Franklin
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1946-04-09
Filing date: 1946-04-09
Publication date: 1951-10-09
Anticipated expiration: 1968-10-09

Description

1951 c. G. BIEBER ETAL 2,570,193

HIGH-TEMPERATURE ALLOYS AND ARTICLES Filed April 9, 1946 4 Sheets-Sheet FIGI. v F|.cs. 2.

F|G.3. FIG-4.

1N VENTORS. CLARENCE G. BIEBER WALTER F. 5U MPTER BY (1 QM Arromws'x Oct. 9, 1951 c. G. BIEBER ET AL HIGH-TEMPERATURE ALLOYS AND ARTICLES Filed April 9, 1946 PERCENT CEEEP PERCENT CREEP 4 Sheets-Sheet 2 u /.0 I; & LL 0.9 k 8 0.8 E 2 0.7 0 Q! 8 0.6 r

o 0.5 S I; 0.4 a

D 0.3 g k 2 0.2 8 Q 0/ 92 C RVE A Q I00 200 500 400 500 600 700 600 900 I000 1200 HOURS AT /200"F I I l l l I l I I I I I I o 06 Q: 0.40 t

q Q 0.30 a g 020 S ALL(\) Y N0.3/ 8

3 ALLOY/v0.8 b 0.10 1

E I l I I l l l l l l l I l HOURS LOADED V NT R.

FIGS.

CLARENCE G.BIEBER WALTER E SUMPTER ATTORNEY Oct. 9, 1951 c. G. BIEBER ETAL 2,570,193

HIGH-TEMPERATURE ALLOYS AND ARTICLES Filed April 9, 1946 4 Sheets-Sheet 5 IOOOO T/ME TO FRACTURE IN HOURS A TTORNEY Oct. 9, 1951 c. G. BIEBER ET AL 2,

HIGH-TEMPERATURE ALLOYS AND ARTICLES Filed April 9, 1946 4 Sheets-Sheet 4 I400 I600 I800 2000 2/00 Q '44 8 Q & a 5 0 9 Q: o LL 5 I 8 U) 8 c0 5 8 0 S 8 "3 8 N r N o o o O (1.7.7273 iNJDE/Eld INVENTOR.

CLARENCE G. BIEBER WALTER F. SUMPTER ATTOQNEY Patented Oct. 9, 1951 257G193 HIGH-TEMPERATURE AIJDYS AND ARTICLES Clarence George Biebcr and Walter Franklin Snmpter, Huntington, W. Va... llignors to 11m International Nickel Company,

Inc., New York,

N. Y., a corporation of Delaware Application April 0, 1046, Serial No. 000.?

' 10 claims. (Cl. 75-471) The present invention relates to alloys particularly suitable for use under load at elevated temperatures, and articles made thereof.

Inrecentyearsthearthasbeenearnestlyendeavoring to obtain creep resistant alloys having heat resistance and high strength at elevated temperatures.- particularly lower creep rates,

longertimetoruptureunderagivenstressat given elevated temperatures. 1. longer fracture life, and/or the ability to withstand higher stresses or loads at a given elevated temperature for a given fracture life, i. e., higher load-carrying capacilar. Thus, a major difllculty in extending vals of time. The moving bladeson the rotors must simultaneously withstand the high s set up by the revolving rotors which may operate at-speeds from 30.000 to 50.000 revolutions per.

minute. At such high speeds, accurate dynamic balance of the rotating parts is essential throughout the life of the turbines. This required balance demands that the rotating parts maintain their shape, size and balance and that the parts he made of alloys which are highly resistant to heat. warping, distortion, growth and creep and are capable of withstanding high stresses at the elevated service temperatures for longer periods of time without fracturing or rupturing.

In determining the suitability of an alloy for the manufacture of gas turbine parts and other articles subjected to load at elevated temperatures, rupture or fracture tests are frequently resorted to. In such tests a number of specimens of the same alloy are loaded with stresses calculated to cause fracture within a, period of time corresponding to the expected useful life of the part atthe temperature at which the part is expected to operate. In the case of gas turbinm for airplane superchargers. the expected useful life has been considered to be between 300 and 1000 hours. Other articles may require different lives varying from a short life of only a few hours to a long life of many thousand hours. In

conducting rupture tests'to determine the suitability of an alloy for gas turbines or other articles, the temperature of test is generally 1200" It. 1350 F. or 1500 F. By thesetests the loads or stresses which will cause fracture within the.desired time limits at the test temperatures are determined.

a re, it hasbcenfoundthattheatelevated temperatures frequently varied considerably and could not be obtained consistently. It was also found that the proposed alloys often tended to be brittle and to lack ductility at the elevated service temperatures. The prior alloys also tended tocontainseams.splits-.andthelikewhichresultedinahighmimberofreiectionsofthe finished articles after i or in premature failure in service whim these defects were not detected during inspecflon. Although many attempts were made to provide alloys having more improved properties at elevated temperatures. none, as far as we are aware. was entirely satisfactory when carried into practice.

We have discovered that an improved combination of high temperature properties. including longer fracture life. can be obtained by employins k l ys ntaininga critical combination of -chromium. aluminum, titanium. columbium and zirconium. and preferably also containing 'ironand It is among the objects of our invention to provide cast and wrought nickel alloys having improved properties at elevated temperatures; to provide nickel alloys having good hot malleabllity or hot working properties combined with improved creep resistance, i. e., improved fracture life. higher load-carrying. capacity and/or lower creep rate; to provide improved heat resistant, age hardenable, wrought nickel alloys having en- 'hanced properties under load or stress for longer intervals of time at elevated temperatures, particularly at temperatures of l200 F. and higher; to provide improved age hardened nickel alloys exhibiting consistently outstanding properties at elevated temperatures. particularly at temperatures of 1350'F. to 1500 I". and higher; to provide age hardened nickel alloys having such improvide high temperature properties that at 1200 F. they are capable of withstanding a load of about 60,000 pounds per square inch or more for at least 1000 hours, at 1350 1". they are capable of withstanding a load of about 40,000 pounds per square inch or more for at least 1000 hours. and at 1500 F. they are capable of withstanding a load of about 18,000 pounds per square inch or more for at least 1000 hours; to provide improved articles of manufacture, particularly wrought articles. subjected in use to stress at elevated temperatures made'of the age hardened nickel alloys provided by the present invention; to provide improved age hardenable alloys having high mechanical properties; to provide an improved heat treatment, particularly a tripl treatment,

for improving the ductility and increasing the time to fractureat elevated temperatures of the nickel alloys contemplated by the present invention; etc.

Other objects and advantages of the invention will become apparent to those skilled in the art from the following description taken in conjunction-with the accompanying drawings in Figs. 1 to 4 are reproductions of photomicrographs taken at 1000 magnifications showing the structure of an alloy contemplated by the invention after various heat treatments;

Fig. 5 containing curves A and B shows the effect of holding time in one step of a triple heat treatment contemplated by the invention:

Fig. 6 depicts curves showing the properties of an alloy within the scope of the invention after various heat treatments;

Fig. 'I is a creep curve of an alloy contemplated'by the invention under a load of 15,000

pounds per square inch at 1500 F.; and

Fig. 8 depicts a pair of creep curves comparing an alloy of the invention with another alloy having a composition not in accordance with the invention under a load of 60,000 pounds per square inch at 1200 F. I V

v The present invention is based on the discovery made'by us that nickel alloys having improved high temperature creep properties can be produced by incorporating in the composition conium, columbimn and zirconium in combination. The alloys preferably also contain iron which when present in amounts exceeding about 4% to 5 has been found by us to be decidedly beneficial and further to raise the high temperature properties in a marked manner. Silicon is also usually incorporated in the alloys. Optionally.

molybdenum may also be present. In general, the alloys provided by the invention contain the aforementioned critical combination of essential elements and other elements within the following ranges:

Element: Percent chromium 10 to35 Aluminum 0.1 to 8 Titanium 0.1 to 8 columbium 0.1" to 8 zirconium 0.002% 2 Iron. 0.1 to25- silicon 0.05 to 8 Molybdenum .0 to 5 Nickel (q-cobalt) Balance sum of the aluminum, silicon and titanium contents should be at least about 2 and not over about 10%- The foregoing ranges are particularly suitable for castings. The aluminum and titanium contents in cast alloys preferably do not V 4 The sum oi' the aluminum, titanium and silicon contentsoithealloystobeworkedshouldbeat least about 2% and not over about 4.5%.

'--It is an essential feature of the invention that the alloys not only contain titanium and aluminum but also at least a small but effective amount .of zirconium and at least 0.10% columbium ,in

order that the improved high temperature properties provided by the present invention be obtained. Tests which have been conducted have established that the slight amount of zirconium is very essential for the improved results of the 1 invention although the minimum amounts retrolled amounts of chromium, aluminum. titanexceed about 5% of either. when the alloys 'are I to be worked into wro t products, the composition should be maintained within the following ranges:

Element: Per cent Chromium 10 to 25 Aluminum 0.2 to, 15 Titanium 1.5 to 3 columbium. 0.1 to 3 zireonium 0.002 to 0.2 Iron 0.1 to 20 Bilicon 0.05 to 0.8

' Molybdenum 0 to 1 Nickel (+cobalt) quiredareassmallasorevensmallerflianaecurately ble by conventional methods of combination with good high temperature properties, it is essential that the columbium content not exceed 3%, that the zirconium content not exceed 0.2%, that the aluminum content not ex-'- ceed about 1.5% and that the met the aluminum content, the titanium content and the silicon content be at least about 2% but not over about4.5%. whilesmallamoimtsofmoiybdenum uptoabout5% maybebeneflci'alforhightemperatureproperties in and where hot workability is not an important factor, molybdenum d hot workability and should not exceed about 1% when hot workability is important. About 0.5% inn has been found bination of high temperatureproperflu ing properties. In general, about 0.2% to 0.0%

small amounts of other element inafter. The nickel content caseswillbeatleastaboutmflabyweight alloys and preferably will beat least 50%. commercial alloys the present tion,partofthenickelmaybereplacedby amounts of other elements. such as metalloilh thesulfurandarsenicgrounleai.

carbon,

pper,coba1t, boronandcalcium,inatotalammtuptoabout 5%. As noted, hereinbefore. in amountsupto5%.preferablynotover1%,may alsobe t. Inaddittontobeingwesent besdded inplaceoi'partoithenickel. Theeontentof metalloidsofthesulfurandarsenbgroupand oflead-shouldheaslowaspossibleI Leadshould preferably not exceed 0.002%. Sulfur should preferably be below 0.01% and more preferably notinexcessofabout0.00'l%.'l'hosphormpref erably should not exceed about 0.025%. The

alloysmaybesubstantiallye'arbon-freaorcab Balance bonmaybepresentuptoaboutmfi'x, andpreferably is maintained below.about 0.10%. Ordinarily, carbon will be present within the range of about 0.02% to 0.06%. Manganese ordinarily will not exceed about 2.5% and preferably will be within the range of about 0.1% to 0.8%, e. g., about 0.5%. The alloys may be substantially copper-free or may contain up to about 2% copper, preferably not over about 0.5%. Ordinarily. any copper present will beas an impurity and will not exceed about 0.15%. Cobalt may be introduced in the alloy along with nickel which often contains small amounts of cobalt up to 1% or 2% or even more. when the extra cost of a cobalt addition can be tolerated, cobalt in amounts up to about 25% may replace nickel. When the alloy is to be worked or used in a wrought form, it is preferred that the cobalt content not exceed about e. g.,' about 10% or less. Magnesium and/or calcium is advantaeously added to the alloy when it is to be hot worked; Magnesium is preferred because it produces consistently good forgeability and creep and fracture properties. It is preferable that the um content of the alloy not exceed about 0.15% as larger amounts render the. alloy very dliiicult to forge or roll. A very small but effective amount of -magnesium, e. g., about 0.002% or less, improves the creep properties, e. g., the creep rate and/or fracture life, and is preferably present. Magnesium in amounts of about 0.01% to about 0.03% is particularly effective, but smaller amounts, e.-g., about 0.002% to 0.008%, have given satisfactory results. Alloys containing very small but effective amounts of magnesium, as small as or even smaller than accurately measurable by conventional methods of analysis, have an improved combination of low creep rates, high fracture lives and good workability compared to similar alloys in which magnesium has not been added. In castings, up to about 0.5% magnesium can be used. The addition of a very small amount of calcium has also been'found to improve the fracture properties but is not as preferred as magnesium. Three comparable alloys containing chromium, aluminum, titanium, columbium, zirconium, iron, sili: con and nickel in approximately the same amounts and within the ranges contemplated by the invention but containing no magnesium, 0.03% magnesium and 0.15% magnesium, respectively, had, after proper heat treatment as set forth hereinafter, fracture lives of 134 hours. 500 hours, and 541 hours. respectively, and had second stage creep rates of 0.004% per hour,

' 0,0003% per hour and 0.0001% per hour, respectively, under a load of 20,000 pounds per square inch at 1500 F, Another heat treated, similar alloy to which about 0.015% calcium was added instead of magnesium lasted for 437 hours at 1500 F. under a load of 20,000 pounds per square inch.

As noted hereinbefore, iron is very beneficial for improved creep properties. when good hot working propertiw, e. g., hot malleability, hot forgeability, hot rolling properties, etc., are especially desired in alloys containing or more chromium and at least 60% nickel, the sum of the chromium and iron contents should be less than about preferably not more than about 26%. Thus, when a nickel-base alloy containing over 60% nickel and having a composition within the ranges contemplated by the invention is made from substantially pure chromium having an iron content of about 1%, the chromium content should not exceed 30%, preferably not over 25%. However, if a standard a about 21% and preferably is not over 18% when the alloy' is to be hot worked. When the nickel content is under 60% and/or the chromium content is not over about 16%, iron and nickel are interchangeable as far as workability or forgeability is concerned. However, for optimum high temperature properties it is preferred that the alloy contain about 4% to 15% iron. 13% to 16% chromium and 64% to 76% nickel in addition to aluminum, titanium, columbium and zirconium and other elements such as magnesium,.silieon, manganese, carbon, etc., as set forth herein. Excellent results are obtained with 6% to 8%.imn, 14% to 16% chromium and 71% to 75% nickel.

'The effect of varying the chromium and iron contents in the base composition of the alloys upon the fracture life at 1500 I". under a high load of 20,000 pounds per square inch and upon the workability of the alloys after proper heat treatment, as dwcribed hereinafter, is illustrated by the following data. the remainder of the composition being nickel in addition to about 2.3% to 2.5% titanium. 0.5% to 0.7% aluminum, 0.0% to 1.1% columbium. about 0.01% to 0.06%sirconium and the usual small amounts of incidental elements and impurities:

Per Cent Chro- Perot!" mm Workabilit Iron Life Y Hours 10. 5 67.5 workable 15 1 11.1 D0. 15 7 400 Do'. 15 15 H6 Do. I) 1 173 Do. I) 3 l3 Do. :0 10 not workable. 26 l 116 dlfllcultly workable.

In carrying .the invention into practice,.it is preferred to maintain the composition within the rangesset forth in the schedule below, whether the alloy is to be used in a wroughtform or as a casting, for example, precision castings made by the process employed in the dental art or modifications of said process. For the production of precision castings, the art frequently'demands .wrought stock. i. e.. bars, rounds, etc.,"which,can

b conveniently cut to the desired size to make up a ,charge, then melted and cast by precision casting methods. The compositions preferably employed in practice are as follows:

Preferred Element Range Rum Example Per cent Per cent Per cent 12 to 18 14 to 10 15 0.2 to 1.5 0.4 to 0.8 I 0.7 1.5 to 3 2.25 01.2.65 2.5 0.10 to 3 0.4 to 1.2 1.0 0.002 to 0.2 0.01 to 0.08 0.05

4 to 20 6 to 8 7 0.05 to 0.8 0.2 to 0.5 0.3 0.1!)1 to 0.15 0.002to 0.03 i 0.03 Balance Balance Balance Amounts up toabout 1% molybdenum, e. g., about 0.5% molybdenum, are the preferred optional contents that can be incorporated in the foregoing compositions. The term -balance in- ,cludes small amounts of other incidental elements and impurities commonly present, as discussed hereinbefore, for example, carbon, manganese, sulfur, copper, etc: Illustrative values a 8 tions. Thus, when aiter hot working, e. g., in large 1, i hi h fandwithintherangessetiorthhereinlor the sbinethehightemperaturetreatmmtwithahot working operation. Byaocurate emtrolot the.

the temperature at which the preeipitable phases which impart age hardenability go into complete solution. Said high temperature treatment comprisesheating the alloy within the range of about 1950' 1'. to 2200 1"., preferably about 2050 I". to 2150' l"., for at least about one hour, more preterabb at least about two hours and up to about 24 hours or more, followed by suiilciently rapid cooling to preserve the solid solution 01 the age lmrdening precipitabie phases. Ordinarily, the

ma is rapidly cooled by quenching in water or oil. However, air cooling is suiiiciently rapid, especiailywhen theservicetemperaturesarel350 l", or lower. When the service temperature is .1500 l"., it is preferred to cool large sections 01' theaiioybyguenching. Smallsections maybe air cooled. In'general, the cooling rate should be such that the alloy will cool to about 1300' 1''. within ten minutes. Ii! desired. the cooling alter any treatment may be interrupted at the temperature or the subsequent treatment and held there for the required time, i. e.. in heat treating thealloysitisnotessentialthatthealioybe cooled from the temperature of one treatment to room temperature and then reheated to the temperature of the subsequent treatment. The alloys alterthe high temperature treatment are subjected to an agi treatment which comprise holding the alloy within the range of about 1300' 1'. to 1500' F. for at least about tour holu's. Prelenablyaboi'iteighthourstomhoursormore. Longer treating times for the higher temperature treatment and the aging treatment than noted hereinbefore are not detrimental but are not The aging treatment imparts high temperature strength at about 1200" 1". and uptoatleastaboutl500l'ttothealloyswhen preceded by the above-ducribed. high temperature n'eannent. It the high temperature treatment is below about 1950' l, for example, at

v 1850' I. the subsequent aging treatment at lower temperatures willnotimpartthehigh-temperature propertiesat1200 l". andhigher oontem-- P i d by the present invention even though the ailoysareagehardened. Thus,anailoy (No. 1) madeinacccrdaneewiththepresentinvention and containing 14.28% chromium, 0.79% aluminum. 2.45% titanium, 0.33% silicon, 1.05% codreonium, 6.91% iron, 0.03% carbon, 0.49% manganme, 0.03% copper, 0.007% suitor and 73.50% nickel ruptured in 99.8 hours underaloadoi'flmpmmdspersqulminchat SWILwhengiIenatreatment iorrourhours 1000'- I'. followed by an aging treatment for homaatls'l whereasthesamealloy uoderthesameloaddflnotmptureuntil after 040 hour-sat 150021. when given a high temor iour hours at the temtreatment. Aswillbeapparenttotlmseskilied intheartfliehkhtemperaturetreatmentmy be outsimnlianeomlywith high temperature treatment, it h possible to comilnishing-temperatureinhotworting,smail articles, e. g., rods, turbinebiadea, etc, can be produeed'having good properties, by combining the high temperature moment with a not workingoperationsuchasrollingoriorlintmvided thehotworkinghflnishedatsumciently. high temperatures, for example, at about 3100' '1'.

Howeventhesmailertheseettonsisethemore diiiicuitisthecontrolottheiinhhiligteniperature-requiredtoproduceresults,

whengoodpropertiesathighservieetenmera tures such as about 1500' 1'. are desired, satisfactory results are obtained by employ a double heattreatment comprising a-high temperature treatment at about 2100 1'. for about tour-hours,

' about 1300' 1". to 1500' I.

coolingbyquenchinginwaterordlorbyair cooling, tollowedbyanaging 1".tol500'l'.

treatment at 1300' ducted at a temperature at least as servicetemperaturetowhiehtheailwisto subjected under load but erties at temperatures below 1300 1". are desired, the a ing temperature preferably should not be below about 1300 IL This, it an alloy employed underload at a service temperature of 1200' it. it is aged at a teinpdature oi 1300 R,

temperaturewillbelower.

'l'heheat treatment whichhasbeen inthepreeeding described may, for convenparagraphs ,ience,bereierredtoasadoubletreatment,i.e...

a high temperature treatment followed by a lower temperature aging treatment. This double treatment gives satisfactory results, particularly when the alioyis being treated for useat service temperatures or about 1500' 1". and higher-or for \me at lower temperatures under the same loadsaswouldbemedataboutWEJor-example, up toabout 30,000 pounds per square inch. However, whentheaiioyistobesubieetedinuse to heavyioadsatthelowertemperamresoi'about 1350' F. to 1200 It, tor example, 50,000 pounds per square inch or more at 1200' l". or 35,000 pounds per square inch ormore at 1350' It, and when longer time to iracture,.decreased brittlenessand/orhIgherdmtiIit'yaIecondstentUd'e sired at the service temperatm'e, particularly at service temperaturu of about 1350 P. and lower,

otheroperaneg at leastdowntoabout 1200' Randeven theiinishingtemperatme e. g., at 1350' stantial amount of plastic fiow in after heat treatment, e. g.,

9 down to 1000' 1'', improved properties are obtained when a triple treatment is employed. This triple heat treatment involves the use between the high temperature treatment and the aging treatment of an intermediate treatment at a temperature above 1450 F. but below 1850 F. The inter- .mediateor treatment, when preceded by the high temperature treatment and followed by the 88 18 treahnent, markedly improves the ductility and/or the time to fracture under load while retaining high strength properties at the elevated tem. Thus, the fracture life of an alloy contemplated by the invention (alloy No. 2 set forth hereinafter) was raised from 85 hours aiter the double treatment to well over 1320 hours '(at which time the test was discontinued without any evidence that the alloy was near the fracture point) after the triple treatment when tested under a load of 54,000 pounds per square inchat 1200 F. The same alloy after the double treatment had a fracture life of 493 hours at 1500 F. underthe heavy load for this temperature of 20,000 pounds per square inch.

In carrying out the triple treatment, the alloy is subjected to the high temperature treatment described hereinbefore; cooled suiliciently rapidfor example, by quenching in water or oil or by air cooling, etc., as described hereinbefore;

given the intermediate treatment at temperatures between about 1800" F. and 1500 F., preferably within the range of 1500 F. to 1700 F., for at least about one-half hour, preferably at least one hour and up to about 24 hours or more; cooled rapidly, for example, by quenching; and then given the aging treatment described hereinbefore.

Treating times of 1 hour, 4 hours, 16 hours, 24

hours and 168 hours in the intermediate treatment have all given improved results. A suitable triple treatment comprises treating the alloy at 2100" F. for about four hours, quenching or air cooling. treating for about 24 hours at 1550" F., 1600 F. or 1650 F., quemhing or air cooling, and treating at a lower aging temperature but preferably not below about-1300 F. for about 16 to 20 hours, I". if that is the service temperature or at 1300 F. if theservice temperature is 1200" F. For general and particularly when optimum ductility at the service temperature isdesired, treatment for about four hours at about 1550 F. is satisf ctory s an intermediate treatment. When low second stage creep rate is more important than ductility, a higher temperature, e. g., 1650 11, may be desirable. When a subthe initial stage is desired or can be tolerated, long holding times. e. g., 168 hours, may be employed in the intermediate treaiment. Such a long-time intermesome applicadiate treatment can be useful in tions where it is desired to cold work the alloy in forming turbine blades by cold Striking. As in the case of the double treatment, it is not emential in the triple treatment that the alloy be cooled to room temperature between heatmen cooled from the temperature of one treatment directlytothatofthenext treatment;

The triple treatment contemplated by the invention will produce the optimum combination of fracture life and creep resistance under heavy loads for service at temperatures in the range of about 1000 F. to 1350 F. However. in some applications where a fine grain size and higher ductility are more to be desired than high loadcarrying capacity, the high temperature treatment may 10 given the intermediate treatment, e. g., within the range of about 1550' F. to 1750 F., and then aged. Thus, when alloy No. 1 was hot rolled and then given an intermediate treatment for 24 hours at 1650 F. and an aging treatment for 20 hours at 1300 F. and then tested under a load of 00,000 pounds per square inch at 1200" F., it had afracture life of 200 hours with an elongation of 6.5% in six inches and a reduction of area of 6.2%. This kind of treatment can be satisfactory for some applications where the design calls for loads of the order of only 30,000 or 40,000 pounds per square inch and where fine grain size and higher ductility are considered to be desirable. Examples of such applications are extrusion dies which in order to resist spelling require sufiicient ductility to withstand the severe thermal stresses encountered in service. Extrusion dies given the foregoing heat treatment without a prior high temperature treatment have performed satisfactorily in use. Another example of when the high temperature treatment may be omitted is in the case of hot worked articles, such as large forgings, where the finishing temperature after hot working is so controlled that a high finish v accomplished from the residual temperature after hotworking. Such a heat treatment can be employed, for example, in producing a 30-inch gas turbine rotor by finishing the hot forging at a highiemperature, e. g., at 2100 1"., and then conducting the intermedia and aging treatments. Even smaller articles, such as rods or turbine blades, which are finished at a high enough temperature after hot rolling or forging can develop good properties by accurate control of the finishing temperature, but, as noted hereinbefore, such control is very diflicult and it is preferred not 1 to combine the hot working operation with the high temperature treatment, particularly when I articles of small section size are being produced.

The intermediate treatment is conducted above 7 the temperature at which age hardening occurs.

' In fact, the treatment is generally accomplished by a decrease in hardness. The intermediate treatment initiates the profuse precipitation of a relatively coarse constituent, which precipitation does not have a hardening efi'ect. Thus, after thee-intermediate treatment the hardnes is of the order of about 160 Brinell hardness number,

e. g., about 140 to 180. whereas after the subsequent 8 treatment at lower temperatures the hardness is about 350 to 400 Brinell hardness number. The precipitation initiated by the intermediate treatment of the triple treatment can be illustrated by reference to Figs. 1 to 4 which depict reproductions of photomicrographs taken at 1000 magnifications showing the structure of an alloy (alloy No. 2) after various heat treatments. Fig. 1 shows the microstructure of the wrought alloy after a high temperature treatment at 2100" I". for four hours followed by rapid cooling. Fig. 2 shows the microstructure of the same alloy after an embodiment of the double treatment contemplated by the invention, i. e., after the aforementioned high temperature treatment followed by quenching and aging at 1300 F. for 18 hours. Fig. 3 shows the microstructure be omitted and the material merely 15 -ment followed by quenching, then an intermediate treatment at 1650 lowed by quenching and F. for 168 hours folaa 881-1 8 treatment at 1500' I". for 18 hours. Fig. 4 shows the microstructure obtainedhhen too high a temperature is employed in the intermediate treatment. The diilerence between the structure of Fig. 2, illistrative of the double treatment. and'that'of Fig. 3, illustrative of the precipitation initiated tripleireahnent, ismarked. InFig.2 moderateamountsoiaveryilnedispersedconstituent are obtained. In Hg. 3 profuse precipitationoi'aeoarsernaturehastakenplace. In addition. "clean" hands tree of visible precipitate are adjacent the grain boundaries. The imved iracture life the alloys subjected to the triple treatment are attributed to the unusual structure initiated or developed by this treatment. when the intermediate treatment is of shorter duration] e. g., 16 or 20 hours, the unusual structurejs not as distinct but is initiated and becomes more evident when the treatment is prolonged. As shown in Fig.4,the immual structure of Fig. 3 is no longer obtained when too b18118 temperature is employed in the intermediate. treatment. the structureinthatcasebeingsimilartothatof m; 2.

The triple treatment contemplated byethe invention improves the properties of the alloys provided by the invention but does not improve the properties of similar alloys devoid of columbium 'and airconlum. Thus, alloy Ho. 8 given'hereinaiterhad a tracturelifeoi'3l2 hoursunderaload oi 54,000 pounds per square inch at 1200'1'. after a double treatment and had a fracture life of only 300 hours under the same test conditions after a triple treatment. The same alloy containing both columbium and zirconium in accordance with the invention would have lasted for thousands of hours under the same test conditions after the and ductility exhibited by subiected to fracture tests at 1350 F. under a:

high load of 45,000 pounds persquare inch. The

following schedule sets forth the results of tests and demonstrates the marked improvement in fracture lite and ductility that can be obtain'edbythetriple treatment:

. Treatment a? ising:

I Hears as an Tripl as: a!

' inch in diameter in the minimum section at the same triple heat treatment. While the theoreticalexplanaflonoftheeiiectsobtainedbytheuse of the intermediate treatment contemplated by the invention-is not fully understood. a possible explanation mentioned hereinbefore in describinsl'igs. l tosisthattheintermediatetreatment initiates the precipitation of a phase in a controlled manner which produces better properties and that when the intermediate treatment is omitted the precipitation is uncontrolled vat lower temperatures during the aging treatment and/orinuse. Themicrostructuresofthealloys andthestructm'esshowninthephotomicrographs oithedrawingsareinharmonywithsuchanexplanation. Whatever the correct explanation, thefacts arethat-theintermediate treatment mprod uces improved properties as described here- Under the microscope the precipitate of Fig. 3

Iii

appeuslight-eolored.i.e..palegreyincolor,and

becauseofthelightcoloroithematrixorback gr'umd. i. e..white, theprecipitate is dimcult to 'fphotograph because of the absence of contrast betweentheprecipitateandthematrixorback careful polishing. etching and photothenetchingthesamewithasolutbncontaining -'about 95% eoneaitrated nitric acid and about databasedonrolledalloyHoJdescribedhere- 15 P.

center portion of the test piece where fracture occurs. This minimum sectionwassixinches'in length and the per cent elongation is the percentage increase in dimension which occurred during the fracture test over the six-inch length. Asiswell knowntothoseskilledinthearhthe per eentelongation will vary with the length over which it is measured, and the same alloy will have higher elongation if determined from a specimen having only 'a .one-inch minimumsection length than when determined over a sixinch or four-inch minimum-section length. From available data, it might be said that, in general,

the elongation measured on a one-inch minimumsection specimenwillbeatleast 1.5to 2timesas large as when measured on a six-inchor fourinch minimum-section specimen.

The high properties obtained by the invention under high loads at 1350 F. and the improvement in fracture lite obtained by the triple treatment are illustrated by the following data from tests at 1350' P. on alloy No. 1' after a double treatmentandafteratripletreatment:

. Iran-um Hours D 40,000 ml D0 A5,!!!) 218 D ELM M Ti'lp 45,!!!) m Data obtained at 1200' I". have ahownthat the triple treatment similarly develops notablyim- Theeiilectontractureliieofvaryingthetem- 'perature'and/or time of the intermediate treatmentinthetripletreahnentisillustratedbythc following data obtainedinfracture tests at 1200 under aloadoi'60mopoimdspcrsll fl' inch as'n'ufio's I3 a l4 onalloyliojhavingthecompositiongivenhere- 'iatigueorendurancelimitetesatelevatedtm inaiter: '1hus,alloyNo.1aiteradoubletreat-- 'llaatmmt v m arr imagine-r mm mmr H an maximemployed. Thus. wrought alloy No. 1 when given a double tratment (4 hours at 2100' F. and 20 hoursat 1300'!) had airacturelii'eoi'mhours go under a load or 25,000 pounds per square inch at 1500' 1". where as when given a triple treatment, involving an intermediate treatment for 24 hours at 1550' I". inadditiontothesame hightemperature and aging treahnents as employed in the as double treatment. the alloy had a iracture life of 212 hours under thesame conditions 0! test.

Theshortand long-time intermediate treat--v mentsarecomparedinFlg.5whereincurveAis thecreepcurvei'oralloyNo.2,setiorthhereinso after, tested under a load oi 54,000 pounds per square inch at 1200' 1'. after a high temperatwe treatment at 2100' F. for 24 hours followed by a short-time intermediate treatment at 1650 I". for

24 hours and annslng ireatment at 1300 1". for as l6hours. CurveBlsthecreepcurveforthesame alloytestedunder thesameloadat i200l".after a heat treatment comprising the same high temperature and aging treatments but a long-time inte treatment at 1650' l". for 108 hours. 40

CurveBtestheabilitytoloadtheheat treatedalloyiarahoveitsyieldpointandstill have the alloy come to an equilibrium where it ethibitsgoodcreeprateinthesecondstageoi creep. Itwillbeobservedthatthealloysinthe ccnditionsotbothcurveAandcurveBwei-estill 45 inthesecondstage oi creep with low creep rates. about 0.015% and 0.20% per 1000 hours. respectively, when the test was discontinued after 1320 hours. After c'old striking a heat treated alloy havingacreepeurvesuchascurvehthecurvei iorthecoldstruck'alloywouldtendiobedisplaced downward totlnt oil-curve A. An alloy exhibitingacreepcurveliketlntoicurveBprovidesasai'etyiactorintheeventci'anunexpected overload. Ingeneralandparticularlywhenlow 55 whenvthe alloys oi the invention mm, 00

below 1200' 1!, to: example, at temperalm-llanddowntoroomtemperatreatments, advantage can be taken of the eiiect I" strength up! 45,400 pounds per square inch at 1500F.a1'terhavingbeengivena douhletreatment. Likewise, hot rolled alloy No. 1 has an endurance limit for one hundred million cycles at 1500' Roi about 34,000 pounds per square inch after a triple treatment comprising four hours at 2100' I"., 24 hours at 1650 I". and 20 hours at 1300 1''. At 1200' I". the endurance limit for one hundred million cycles, after a triple treatment, is approximately 05,000 pounds per square inch.

The recrystallisation behavior oi the alloys oi the present invention containing columbium and zirconium is diiierent from that of similar alloys devoid oi coiumbium and zirconium. The alloys oi the present invention recrystallise at about 1850 I". to a'medium grain size of about-No. 6

accordingtotheA.8.T.ll.standardgralnsise classification iorsteels,andthegrainsirebecomes gradually larger at successively higher temperatures. The alloys devoid oi columbium and zirconium recrystallize at about 1050' I". to

alargeexaggeratedgrainsiseoi'aboutNo. 3 accordingtotheA.B.T.ll.standardgrainsise on for steels.

Theirachireoithealloysoithepresentlnvention is also diiierent from that of similar alloys devoidoi columbium and zirconium. The alloys 01' the invention containing zirconium and columblum tend in general to break with a transcryatalline fracture, whereas the alloys devoid of columbium and zirconium break with a coarse intersranular fracture. As pointed out hereinbetore. the response to .the triple treatment of the alloys devoid of columbium and zirconium isverydiii'erentimmthatoitbealloysodthe invention containing these elemen The co-presence oi columbium and zirconium in combination with chromium, aluminum and titaniumintheproportionsprovidedhythe'presentinventionincreasesthetrachireliteilveto tentimesthatotaimllarcompositionsireeirom eolumbium and zirconium under most conditions oiloadandtemperaturewithintherangeemplayed in high temperature applications. for example, in m turbine design. The co-presence oicolumbiumandairconiumalsoincreasesthe load-carrying capacity oi the alloy at temperaturesintheorderof1350'ltto1500'llasmuch astwicethatoiasimilaralbyireeiromcolumbium andzirconium.

The necemity tor, and the improved results 15 illustrated by data obtained on the alloys:

following When the composition is in accordance with the invention, as illustrated by alloys Nos. 1 to 7.

the alloys exhibit much longer fracture or rupt D olmlmmn ture lives for a given load and withstand much I 5 higher loads for a given life than alloys of simi 1 2 3 4 5 7 lar base composition which do not contain the 76 as a u m 58 combination of special elements in the amounts 1420 1452 14 a 0.10 001 0.00 0.11 0.01 0.10 0.00 set forth herembemre- 245 2.50 240 2.50 2.40 2.40 2.00 The fracture properties that can be obtained 3-3; 3;}; g g; g3} ,1,: W m 10 by the invention at 1200 n, 1350* F. and 1500 001 1.00 1101 1.05 1.20 1110 1.01 F. under various loads are illustrated graphically 3: 3: 2: 33g 3: :51: in Fig. 6 which depicts curves based on data ob- 0.00 0.04 0.05 0.04 0.04 0.05 0.05 tained on alloy No. 1. The various heat treat- ,2: 2:2 2; 2:2 2:2 8:3 2:: ments employed in obtaining the data for these 13.50 10.51 13.30 13.04 11.50 01110 1212 5 curves were as follows:

Alloy Composition am" I Heat Treatment Element, per cent v 1,000.1". 4 11 4 a aigm 13011- cooled, 24 hrs. at 1,550 F., 20 hrs.

8 4 3% 3'32 6 &2: 3?: 3-3 1. 4 hrs. at 2,100 F., 24 hrs. at 1,550 F. to 1,050 F., 20

2.42 2.11 253 as? 0.20 2.26 $811,300 none none L 18 none 4 none 2. 24 hrs. at 2 100 1 10 1114. 5: 1,300" 1. one one one 0.05 0'02 1,500..." 4 hrs. at 2,100 F., air cooled, 20 hrs. at 1,00! F.

010 011 7.82 000 1.21 0.40 25 5 0. 52 0. 52 0.51 0.51 0.50 052 1%: :3}; f} :f'fi 3% $5; The improvement obtained by the triple treat- 0.13 0.53 0.55 0.11 0.40 041 ment of the invention is well illustrated by the 23,-, ,;;g,- 3:25 1; 1? two curves at 1350? F. comparing the'same alloy after a triple treatment (1) and a double treats. a.'-usmi small amount, included as .:-'Alloys Nos. 1 to '7 inclusive, have compositions iii-accordance with the invention. and alloys Nos.- 1 to 6 contain amounts of chromium and iron within the preferred ranges for these elemerits. Alloys Nos. 8 to 13, inclusive, have compositions outside the scope of the invention and are included tor-comparison purposes. Alloys Nos. 8 to 12 can be ccmparedwith alloys Nos. 1 to 6 while alloy No. 13 canbe compared with alloy No. 1. All the alloys were heat treated within the temperature ranges set forth here- 'inbetore and were then subjected to tracture or rupture tests. The results of the tests are summarized in the following schedule and illustrate the improved properties obtained with the alloy compositions of the invention which contain eolumbium and zirconium in addition to at least about 2% of titanium plus aluminum:

Alloy Temper- Load, Life to Rup- No. ature, F. p. a. i. ture, Hours 2 1,350 35,(D0 over 1 1,878 1 1,350 45100 832 1 1,360 50,111) M l 1, 350 v 515,11!) 146 5 l, 500 15,000 2,110 '1 1, HI) 20,1110 848 4 1, 500 20.000 401 6 1, 500 20.000 582 l 1, 25,000 21]) l 1,5(1) 30,011) 112 Tut discontinued at 1,878 hours.

ment (2).

The present invention provides alloys, and articles made thereof, which exhibit low second stage creep rates. The following are illustrative of the creep rates obtained by the invention:

r emperar0011 ate,

M107 p. 11.1. ture, F. Per Cent Pcr Hour Alloy No. 14 contained about 16.1% chromium, 0.7% aluminum, 2.5% titanium, 1% columbium, 0.045% zirconium, 1.3% iron, 0.4% silicon, 0.05% carbon, 0.6% manganese and 71.2% nickel. In comparison, heat treated alloys having compositions devoid of colu mbium and/or zirconium or containing insuillcient amounts of titanium plus aluminum exhibited the following second stage creep rat l I Load '1 6??? emperatee a Alloy No. i' ture, F. Per ent Per Hour The creep curve of alloy No. 5 under a load of 15,000 pounds per square inch at 1500 F. is shown in Fig. 7. The alloy was heat treated for 24 hours at 2100 F. and then for eight hours at 1500 F.. In Fig. 8 the creep curve for alloy No. 3 under a load of 60,000 pounds per square inch at 1200 F. is compared under the same conditions with the curve for an alloy (No. 8) out- 15 side the scopeoi this invention.

The high load-carrying'capacity of the alloys and articles provided by the invention is indicated in the following schedule:

smss' for- .'Im 1,000 hr. 100 hr.

' Life Life As pointed out hereinbeiore, for service at temperatures 01 about 1000 F. or lower, the alloys may simply be aged without previous treatment at higher temperatures. For many purposes, such a treatment is preferred as it produces higher properties. Thealloys of the invention do not require a high temperature treatment or even a conventional solution treatment prior to the aging treatment to develop age hardening and can be aged without prior heat'treat- The wire in the "as drawn condition was capable of wrapping around its own diameter indefinitely without breaking. This is the highest tensile strength we are aware oi! in a nickel-base alloy which is. capable of withstanding this test. These high properties render the alloy suitable tor various applications, including armature binding wire, bicycle spoke wire, etc., where such an optimum combination of high properties is required. The high properties at room temperature exhibited by the alloys of the invention make them useful for numerous room temperature and atmospheric temperature applications. The alloys attain a higher level oi. hardness after aging than similar alloys devoid of zirconium and columbium. The hardenability of alloy No. 1 made in accordance with the invention is compared with the hardenability of a similar alloy (No. 16) devoid of zirconium and columbium in the following schedule after aging hot rolled rods made thereof for various periods 01' time at 1300 F.:

ment. This is illustrated by the data in the 101- Views Ham lowing schedules showing the high mechanical g ness Number properties obtained by the invention in shortx x' e 300 time tests at 900 1''. and also at room tempera- Alloy Alloy ture. Thedata at 900 F. were obtained on al- Na loy No. 15 containing about 15.74% chromium, 0.66% aluminum, 2.40% titanium, 1.00% colum- ;h',f gggbium, 0.045% zirconium, 7.22% iron, 0.45% silig a a con, 0.04%carbon, 0.59% manganese and 71.74% 17 398 360 32 nickel. 4o hm g2 33;

Condition 35 Alloy No. 16 containedabout 14.45% chromium, gilisfitidufilfiot tfilifififi'ia 1,aon F. for a ummua ma 6.20% iron, scon,. car ,.8umanganese n m h u8$$fi$fi3fii3iii2$fi2fu321,510 1 .101 and 7 i kel. I 40 Other physical properties of the alloys provided E3? t?" 33:" '1'. s., p. 5.1. Y. S.,p.s.i. gg? gt IVHN 15 000 A 176,800 11.0 45.2 10 000 B 143,100 25.0 31.0 1 room 0 100,000 130,000 25.1 43.1 m 1 room 1) 100,000 100,000 11.0 20.0 404 'r.s.- I Y. a xl smu gth (0.2% 0am). EL-elongation in 2 inches. R. A -rednction in area VHN- Vickers hardnessnumber.

The alloys provided by the present invention have exhibited good fracture lives at 900 F. under heavy loads Thus, a hot rolled and aged alloy having a composition similar to thoseoi alloys No. 1 to No. 3 was loaded to 130,000 pounds per square inch at 900 F. and was still under test after 1200 hours without showing any indications oi fracture.

In addition to their exceptional high temperature properties, the alloys of the invention also possess exceptionally high physical properties at room temperature. For example, some wire (0.070 inch in diameter) made or an alloy similar to alloys No. 1 to No. 3 exhibited the following properties after being cold drawn 75% and then subsequently aged at 1250 F. for four hours:

by the invention which are useful in designing articles made of the alloys are as follows:

Modulus of Elasticity (p. 0.1.) in tension in torsion at F 31x10 11x10 at 300 F 1 29. 8X10 10.6)(10 Coeificient of Ex ion instanta- (inch/inchl noon! 1 1 Coeflicient at indicated temperature. I Mean eoeificient from room to indicated temperature;

loys at high temperatures are notable.

The alloys contemplated by the invention combine high properties, as indicated hereinbefore, with the high corrosion and oxidation resistance which characterize nickel-base" alloys 01 nickel and chromium, with 01" without iron. Thus, the

alloys exhibit outstanding resistance to oxidation at the service temperatures as well as resistance foatmospheric corrosion or tarnishing. The latter Property combined with the ability to take alh igh' polish makes the alloys suitable as metallicmirrors and reflectors in marine atmospheres' and the like, for example, as reflectors in large s'earchlights, etc., which operate at rather high temperatures. Thus, large searchlight reflectors have to withstand the heat which accompanies the generation of millions of candle power and become quite hot in service. The high room temperature and elevated temperature strength properties make the alloys well suited for springs operating at atmospheric temperatures and/or elevated temperatures. I

The alloys of the invention may be employed as cast alloys or castings but are especia ly useful as wrought products, having suitable hot and cold workability when maintained within the ranges of composition and in the proportions described hereinbefore. In forging or otherwise hot working the alloys, they should be worked within the range of about 2225 F. down'to about 1800" F., preferably not below about 1900 F.

The combination of high properties obtainable by the invention makes the alloys suitable for a wide variety of articles subjected in use to load at elevated temperatures and/or at atmospheric temperatures. Such articles include plates, sheets, strips, rods, wires, bars, tubing, forgings, stampings, extrusions, castings, etc., and products manufactured therefrom. Specific examples of such manufactured products include parts of steam turbines, gas turbines (including superchargers), jet propulsion engines, etc., such as moving or stationary turbine blades, buckets and nozzles (including precision cast buckets, etc), turbine rotors, turbine wheels, turbine bolts, combustion chambers or flame tubes, shrouding, bellows, etc.: parts of internal combustion engines, such as valves, valve seats, valve springs, etc; parts of machines and a paratus operating at elevated temperatures, such as springs, extrusion dies, mandrels, piercer points, dummies (for extrusion presses), dies and anvils for forging and drop forging, cutters for hot metal, furnace parts. large searchlight reflectors, etc su ports and elements in radio tubes, incandescent lamps, electronic tubes, etc.; springs operating at elevated temperatures and/or atmospheric temperatures, including valve springs, springs in automatic rifles, springs in torpedoes, springs in measuring and indicating instruments, etc.; bolts; music wire, armature binding wire, bicycle spokes and other wire products; metallic mirrors and reflectors; etc.

- Although the presentinvention has been de-' scribed ill-conjunction withpreferred embodiments, it is to be understood that modifications and variations may be resorted to withouLdeparting from the spirit and scope of the invention, as those skilled in the art will readily understand. Such variations and modifications are considered to be within the purview and scope of the invention and the appended claims.

We claim:

1. An article subjected in use to stress at elevated temperatures made of an age hardened alloy containing 10% to 25% chromium, 0.2% to 1.5% aluminum, 1.5% to 3% titanium, up to 0.25% carbon, 0.1% to 3% columbium with the columbium content being at least ten times the carbon content, a small but eilective amount up to 0.2% zirconium, 0.1% to 20% iron, 0.05% to 0.8% silicon, and the balance essentially nickel, the sum of the aluminum, titanium and silicon contents be ng to 4.5% of the alloy.

2. An age hardenable alloy containing 14% to 16% chromium, 0.4% to 0.8% aluminum, 2.25% to 2.65% titanium, up to 0.1% carbon, 0.4% to 1.2% columbium with the columbium content being at least ten times the carbon content, 0.01% to 0.8% zirconium, 6% to 8% iron, 0.2% to 0.5% silicon, 0.002% to 0.03% magnesium and the balance essentially nickel.

3. An age hardenable alloy containing 14% to 16% chromium, 0.4% to 0.8% aluminum, 2.25% to 2.65% titanium, up to 0.1% carbon, 0.4% to 1.2% columbium with the columbium content being at least ten times the carbon content, 0.01% to 0.08% zirconium, 6% to 8% iron, 0.2% to 0.5% silicon and the balance essentially nickel.

4. An age hardenable alloy containing 13% to 16% chromium, 0.4% to 0.8% aluminum, 2.25% to 2.65% titanium, up to 0.1% carbon, 0.4% to 1.2% columbium with the columbium content being at least ten times the carbon content, a small but efiective amount up to 0.08% zirconium, 4%. to 15% iron, 0.2% to 0.5% silicon and the balance essentially nickel.

5. An age hardenable alloy containing 12% to 18% chromium, 0.2% to 1.5% aluminum, 1.5% to 3% titanium, up to 0.25% carbon, 0.25% to 3% columbium with the columbium content being at least ten times the carbon content, 0.002% to 0.2% zirconium, 4% to 20% iron, 0.05% to 0.8% silicon, the sum of the aluminum, titanium and silicon contents being 2% to 4.5% of the alloy, a small but effective amount up to 0.15% magnesium and the balance essentially nickel.

6. An age hardenable alloy containing 10% to 25% chromium, 0.2 to 15% aluminum, 1.5%

to 3% titanium, up to 0.25% carbon, 0.25% to 3% columbium with the columbium content being at least ten times the carbon content, 0.002% to 0.2% zirconium, 4% to 20% iron, 0.05% to 0.8% silicon, up'to 0.15% magnesium, and the balance essentially nickel, the sum of the aluminum, titanium and silicon contents being 2% to 4.5% of the alloy.

'7. An age hardenable alloy containing 10% to 35% chromium, 0.1% to 5% aluminum, 0.1% to 5% titanium, 0.05% to 8% silicon, 0.002% to 2% zirconium, up to 0.25% carbon, 0.25% to 3% columbium with the columbium content being at least ten times the carbon content, 0.1% to 25% iron, up to 0.5% magnesium, and the balance essentially nickel, the sum of the aluminum, titanium and silicon being 2% to 10 of the alloy and the nickel content being at least 40% of the alloy.

arm es 8. An age hardenable alloy containing 10% to 35% chromium. up to 25% iron, 0.1% to 8% aluminum, 0.1% to 8% titanium, up to 8% silicon, a small but eil'ective amount up to 2% zirconium, up to 0.25% carbon, 0.1% to 5% columbium with the columbium content being at least ten times the carbon content, up to 5% molybdenum, up to 2.5% manganese, up to 2% copper, up to. 25% cobalt, and the balance essentially nickel, the

sum of the aluminum, titanium and silicon being 2% to 10% of the alloy and the nickel content being at least 40% of the alloy.

9. The alloy specified in claim 8 in which magnesium is present in a small amount up to 0.5% of the alloy.

l0."An age hardenable alloy containing 10% to 25% chromium, up to 25% cobalt, 1.5% to 3% titanium, 0.1% to 1.5% aluminum, up to 0.25% carbon, 0.1 to 3% columbium with the columbium content being at least ten times the carbon content, up to 0.8% silicon, 0.002% to 0.2% zirconium, up to 20% iron, up to 2.5% manganese, up to 1% molybdenum, up to 0.03% of metal from the group consisting of magnesium and calciuln, and the balance essentially nickel, the sum of titanium, aluminum and silicon being at least 2% of the alloy and the nickel content being at least 40% o! the alloy.

' CLARENCE GEORGE BE'BER.

WALTER FRANKLIN BUMPIER.

a nmmcns man The following references are of record in the tile 0! this patent:

UNITED STATE PATENTS Number Name Date 1,674,959 Dean June 26,- 1928 1,910,309 Smith et al May 23, 1933 1,920,432 Pilling et a1 Aug. 1, 1933 1,924,245 Koster Aug. 29, 1933 2,018,520 Halliwell Oct. 22, 1935 2,044,165 Halllwell June 16, 1936 2,048,167 Pilling et a1 July 21, 1936 2,048,847 Feussner et a1. July 21, 1936v 2,246,078 Rohn et al June 17, 1941 2,373,490 Mohling Apr. 10, 1945 2,397,034 Mohling Mar. 19, 1946 2,398,678 Thielemann Apr. 16, 1846 2,423,738 Thielemann July 8, 1947 2,489,718 Edlund et al. 1 May 10, 1949 2,481,976 Cape Sept. 13, 1949 FOREIGN PATENTS Number Country Date 371,334 Great Britain Apr. 13-, 1932 510,154 Great Britain July 24, 1939 540,795 Great Britain Oct. 30, 1941 572.779

Great Britain Oct. 25, 1945

Claims

1. AN ARTICLE SUBJECTED IN USE TO STRESS AT ELEVATED TEMPERATURES MADE OF AN AGE HARDENED ALLOY CONTAINING 10% TO 25% CHROMIUM, 0.2% TO 1.5% ALUMINUM, 1.5% TO 3% TITANIUM, UP TO 0.25% CARBON, 0.1% TO 3% COLUMBIUM WITH THE COLUMBIUM CONTENT BEING AT LEAST TEN TIMES THE CARBON CONTENT, A SMALL BUT EFFECTIVE AMOUNT UP TO 0.2% ZIRCONIUM, 0.1% TO 20% IRON, 0.05% TO 0.8% SILICON, AND THE BALANCE ESSENTIALLY NICKEL, THE SUM OF THE ALUMINUM, TITANIUM AND SILICON CONTENTS BEING 2% TO 4.5% OF THE ALLOY.