US2513468A - Alloy articles for high temperature service - Google Patents

Description

Patented July 4, 1950 ALLOY ARTICLES FOR HIGHTEWERATURE SERVICE Russell Franks and WilIiam QIBinQer, Niagara Falls, N. Y., assignors, byfln'iesne assignments, "-to Union Carbide and Carbon Corporation, a

' corporation of New York No Drawing. Application Mays, 194s,

Serial No. 668,328

This inventionrelates to alloy articles designed particularly for use in applications where great strength "at very high temperatures is required.

The .contjinueddevelopment of such devices as superchargers, gas'turbine s, jet propulsion apparatus and thelikedepends upon the production of workable metals-andpalloys that are strong at the high temper'aturesat which such devices operate. Although several alloys have been proposed foruse in high temperature applications, the utility of such alloys has be'enlimited either because they are (not hot-workable or machinable or because theybecomefbrittle upon continued exposure to elevated temperatures. One characteristic of highly alloyed ferrous metals which complicates the problem considerably is that as the ferrous solid solution is more heavily loaded with alloying materials to increase the high-temperature strength, thehighetemperature stability tends to decrease so that upon rolonged heating-the material. .becomes unduly brittle.

There. .is accordingly, a. need for hot-workable, machinable alloy articles having great strength and stability at highly elevated temperatures, and it is the principal object of this invention to satisfy this need.

This object is achieved by the present invention which comprises a ferrous alloy containing chromium, nickel, cobalt, tungsten, and at least one ;metal from the group consisting of columbi-um, tantalum,titanium, and vanadium, together with minor quantities of manganese, silicon, molybdenum, carbon, nitrogen. and impurities commonly-present in steels ofgood quality.

Specifically, the alloy of .theflpre'sent invention contains by weight 15% to 25% chromium; 15% to 25% nickel; more than 25% but not more than 45% cobalt; more than 7.5%,- preferably more than 10%-,'but .notmore than 15% tungsteman aggregate of..0-5.%..t o 3% of one or. more of the elements columbium, tantalum, titanium, and vanadium; and u ,,.to.2% manganese, up to 1% si1icon,.up. to 0.35% carbon, 0.05 %,t 0.25% nitro gen; and theremaindersubstantially all iron and mc'identaljimpurities. Up toa'bout 3.5% molybdenum may bepresent, but addition molybdenum imparts no substantial benefit. The content of any single element of the columbium, tantalum. titanium, vanadium group should be less than 2%, and the titanium content should not exceed 1.5%. Somewhat more of the minor constituents than the upper limits just specified may on occasion be used. For instance, if excellent forgeability is not essential, the carbon content may be above 0.35%, up to say 1%. Iron is present in '3 Claims. (Cl. 75-422) asubstantialproportion, the iron content being at 'least 5 Alloys within the foregoing composition ranges arereadily forged,'welcled, and machined 'and', as has been demonstratedby test, have remarkably great strength and stability 'athigh temperatures, for example 1'200'F;"an'd upwards. Machine parts of the alloys may be designed "toioperate at high stress 'for'long periods of "time at 15001. and at lower stress for moderate periods at somewhat higher "temperatures. The invention includes" cast or hot-worked articles andwelded articles for use at elevated temperatures "and composed of such alloys.

A useful test for'determining the suitabilityof meta-Is and alloys for high temperature applications is the so-"called stress-rupture test; In this test, each 'ofseveral samples of atgiven material is' subjectedto a'measured tensile stress at a particular elevated temperature, and the time r'equired'for thesampleto' fail underthese. conditions of'temperaturefand stress is'-'noted. The data obtained are then plotted, using time and stress as abscissa and-ordinate respectively. A curve is thus established 'for the material: tested, showing for the selected temperature the time requiredt'o causefailure of 'the' material when a particular stress is applied. Usually curves are established for several different temperatures, and fromthese curves can be predicted quite accurately the length of time the material can Withstand failure at a givenstres's applied'at a given temperature. This 'info'rmati'on'is valuable for design purposes, especially if the'material selected may be subjected to overheating, overloading, or both.

The alloy of theinven'tionhas beenshown'by stress-rupture tests to have excellent strength at high temperatures and the ability to withstand large stresses for prolonged periods'of time at high temperature. Forexample, in'one test a specimen of an alloy containing about 20% chromium; 20% nickel; 40% cobalt;'3% molybdenum; 12% tungsten; 1% columbium; 0.16% carbon; and 0;09% nitrogen, remaindersubstantially all iron withstood a stress of 20,000 pounds per square inch at a temperature of 1500 F. for 1485 hours before failure. This specimen had been hot forged and then heated one hour at about v 2300" F. and quenched in water before testing.

The alloy of the invention may be forged or otherwise hot-worked without difficulty in the range of 2100 F. to 1600 F. In some cases working should be continued to a temperature somewhat below the recrystallization temperature this invention is that it may be welded by ordinary Welding methods including the various electric arc and oxyacetylene fusion-deposition methods, submerged-melt electric methods and solid-phase pressure welding methods-thewelds produced being sound, tough, and ductile both in" the weld zone itself and in areasadjacent to'and remote from the weld zone.

To ensure the attainment of the desirable characteristics of the alloy of the invention it is most- 4 or more of the elements of the group consisting of columbium, tantalum, titanium and vanadium, the amount of any single element of the lastnamed group being less than 2% of the alloy except the titanium content being not in excess of 1.5%; up to 2% manganese; up to 1% silicon; up to 0.35% carbon; 0.05% to 0.25% nitrogen;

' and the remainder iron and incidental impurities, the iron content being at least 5%.

2. A heat resistant alloy article which in normal use is exposed to elevated temperatures of 1200 ments can not satisfactorily be ofiset by increasing the proportions of cobalt and nickel in the alloy. Accordingly, care should be taken that the-composition limits described be observed in making the alloy.

If the alloy isintended for uses in which it will be exposed to temperatures not in excess of about 1350 F. compositions near the lower limits of the ranges given may be used, but if the alloy will be used where exposure to temperatures above.

1350 Fjis probable, compositions near the upper limits of the ranges given should be employed. If the alloy is to be used where temperatures not in excess of 1200" F.wil1 be encountered, it may be used in the cold hot-worked condition, but where exposure to temperatures above 1200 F. is expected, the'alloy should be annealed'at a temperature of about2200 F. to 2320 F. before use for best service.

Typical of articles for which the alloy of the invention 'is well suited are blades; wheels and other parts of turbines. Such articles may be either cast or wrought.

Although particular'emphasishas been laid on the hot working properties of the alloy of the invention and the use of the alloy for wrought articles, castings of the alloy also possess very useful properties at high temperatures.

'We claim: Y

1. A heat resistant alloy article which innormal'use is exposed to elevated temperatures of 1200 F. and upwards and has great strength and stability when subjected to high'stresses at such elevated temperatures, said article being com- 3 posed of a machinable, weldable, hot-workable al- F. and upwards and has great strength when subjected tohighstresses at such elevated temperatures, said article being composed of a hot-workable alloy consisting of 15% to 25% chromium; 15% to 25% nickel; more than 25% but not more than 45% cobalt; at least 10% but not more than 15% tungsten; up to 3.5% molybdenum; 0.5% to 3% in the aggregate of one or more of the elements columbium, tantalum, titanium and vanadium, theamount of anysingle element of the last named group beingless than 2% of the alloy except the titanium content not exceeding 1.5%; manganese in an effective proportion up to 2%; silicon in an effective proportion up to 1%; carbon in an effective-proportion not exceeding 0.35%; 0.05% to 0.25% nitrogen; the remainder .ironand incidental impurities, the iron contentbeing atleast 5%.

3. A heat resistantalloy article which inner mal use may be exposed for a prolongedv period oftime to an elevated temperature ofthe order of 1500 F. while subjected to high stressof the order of 20,000 ps. i. at such temperature for such period of time, said article having great strength under such conditions and composed of a hot-workable alloy consisting substantially of 20% chromium; 20% nickel; 40%, cobalt; 3% molybdenum 12% tungsten; [1% columbium; 0.16% carbon; 0.09%,nitrogen; remainder iron.

vR SELL FRANKS.

WILLIAM 0. BINDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- OTHER REFERENCES Kinzel and Franks: Alloys of Ironand Chromium, vol. II, 1940, pages 87, 88, 180,192, 194, 455', published by McGraw-Hill Book Co.,. N. Y.

Progress Report on NDRL Research Project, NRC8, P. B. 39, 578, October 7, 1942, pages 1-21 inclusive (particularly page 5); Declassified to open January 28, 1946.

Claims (1)

1. A HEAT RESISTANT ALLOY ARTICLE WHICH IN NORMAL USE IS EXPOSED TO ELEVAQTED TEMPERATURES OF 1200*F. AND UPWARDS AND HAS GREAT STRENGTH AND STABILITY WHEN SUBJECTED TO HIGH STRESSES AT SUCH ELEVATED TEMPERATURES, SAID ARTICLE BEING COMPOSED OF A MACHINABLE, WELDAVLE, HOT-WORKABLE ALLOY CONTAINING: 15% TO 25% CHROMIUM; 15% TO 25% NICKEL; MORE THAN 25% BUT NOT MORE THAN 45% COBALT; AT LEAST 10% BUT NOT MORE THAN 15% TUNGSTEN; AN AGGREGATE OF 0.5% TO 3% OF ONE OR MORE OF THE ELEMENTSL OF THE GROUP CONSISTING OF COLUMBIUM, TANTALUM, TITANIUM AND VANADIUM, THE AMOUNT OF ANY SINGLE ELEMENT OF THE LASTNAMED GROUP BEING LESS THAN 2% OF THE ALLOY EXCEPT THE TITANIUM CONTENT BEING NOT IN EXCESS OF 1.5%; UP TO 2% MAGNESE; UP TO 1% SILICON; UP TO 0.35% CARBON; 0.05% TO 0.25% NITROGEN; AND THE REMAINDER IRON AND INCIDENTAL IMPURITIES, THE IRON CONTENT BEING AT LEAST 5%.