US3166414A - Tantalum base alloys - Google Patents

Description

United States Patent Office 3,166,414 Patented Jan. 19, 1965 TANTALUM BASE ALLOYS Leonard L. France, Wilkinsburg, and Lee S. Richardson and Duane H. Feisel, Monroeville, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, 1a., a corporationof Pennsylvania Filed July 9, 1962,

No Drawing.

- v 4 Claims. (Cl; 75-174) a This is a continuation-in-partof our No. 20,709, filedApr'il 7, 1960, nova abandoned.

The present invention relates totantalum base alloys suitable for usein applications where high strengthut.

EXAMPLE 1 I 1] An alloy of the following composition was prepared by non-consumable arc melting: 92% tantalum, 4% tungsten,

and 4% hafnium. Samples of the resulting ingot gained an average of 101 milligrams per square centimeter of surface per hour upon being subjected to la blast of hot undried flowing'air for one'hour at a temperature of 2190 F. "Theisamples had an average hardness of 212 in the as-cast condition and 243 after annealing at 2000" C. for '16 hours .in a vacuum of approximately 5 'l0 millimeters. of, mercury. The samples were hot workable at 1200 C. to eifect 'a 60% reduction in thickness.

EXAMPLE II .-An alloy of the following composition was prepared by non-consumable arc melting: 84% tantalum, 8% tungsten, 8% hafnium. Samples of the resulting ingot' 1 had an average weight gain of 24 milligrams per square gas turbines is dependent uponthe availability of such" alloys.

In accordance With-this inveiltiomit has been found that workable alloys possw sing unusually high oxidation;

resistance and strength at temperatures above. 2000 can be produced by alloying tantalum, hafnium, and tungsten, and, if desired, rhenium in specified proportions.

Therefore, the object of this invention is to provide workable alloys which possess high oxidation resistance and strength at elevated temperatures, comprising predetermined proportions of hafnium, and tungsten, with or without rheniumfthe balance, over -50% by weight being tantalum, with'incidental amounts of'impurities.

Other objects of the'invention will, part, be obvious and will, in part, appear hereinafter. 1

In accordance with the present invention ternary tantalum base alloys have been produced comprising from 2 to 8% by weight of hafnium, from 2 to 10% by weight tungsten, and the balance being tantalum, with small amounts of incidental impurities and the alloy may include up to 10% rhenium; The alloys are characterized by high mechanical strength and good oxidation resistance at elevated temperatures, and the ability to be' easily wrought to shape by hot or warm working, or in certain alloy compositions, by cold working.- Inna. preferred embodiment, the alloys of this invention comprise from 2 to 4% by weight hafnium, from 7 to 9% by weight tungsten and v the balance being tantalum, with small amounts of incidental impurities.

The alloys may be melted by one of several procedures which will insure homogeneity and a minimum of contamination. For example, unalloyed, high purity, tantalum together with the proper amounts of pure tungsten and hafnium can be fed into a conventional non-consumable arc melting furnace containing an inert atmosphere, such as argon, or vacuum. The resulting ingot should be remelted several times, preferably bynonconsumably arc-melting it, to achieve homogeneity, then may be hot worked to the desired shaped. The alloy may also be prepared by levitation melting of a ball or rod of the alloy, using induction heating. Electron beam melting or consumable arc melting of the alloys is also satisfactory. Y e i The following examples are illustrative of the present centimeter of surface per-hour during exposure to a blast of hot undried flowing air for one hour at a temperature of 2190 F. The average hardness of these as-cast specimens was 289 and measured 353 after annealingforldhours at 2000" C. in a vacuum of approximately 5 10 millimetersof mercury; The samples also had a 53% reduction inarea after but working at 1200 C.

EXAMPLE in An alloy of the following composition was prepared by non-consumable arc melting: 90% tantalum, 8% tungsten and 2% hafnium. A number of samples of the resulting ingot were reduced 95% and stress relieved at 2000 F.

1 for one hour. The samples were tested for strength and ductility at various temperatures.

The results of these tests are shown in Table -I.

Anothergroup of samples were cold rolled to 90% reduction and each sample was annealed for one hour at a different temperature. The samples were tested for invention. In these examples, percentages given for the. composition are by weight'and' the'hardness values are diamond pyramid hardness (DPH) strength and ductility at room temperature. The results of these tests are shown in Table II.

Table II r Annealing 0.2% Yield mutilate Percent Temperature DPH Strength Tensile Elonga- (lr.s.i.) (k.s.i tion As Renee"- 373 159. e 167. 2 4. 4 2,000 F.- 306 125 131 12. 8 200 291 122 10.9 2,400 229 88. 9 s1. 3 2s. 1 2,700 232 90.4 91.9 30.8 3,00o 273 87. 3 as. s as. 4

In addition, the following alloys were prepared as in Example I and were tested for their strength and elonga- 'tio'n properties.

RT 2700 F.

Ta W Hf Ult. Ten. 0.2% Percent Ult. Ten. 0.2% Percent Strength Yield Elong. Strength Yield Elong.

' Strength Strength I The results indicate that tantalum base, alloys com prising less than 10% tungsten and 8% hafnium have:a

Combination of relatively high strength andihigh ductilityi at room and elevated temperatures and the alloys com prising greater proportions oftungsten and hafnium have relatively poor ductility at both room and elevated temperaturc's. A ductility of 2% to 4%elongation is very" low and renders the use of the alloys'for structunal members dangerous.

It should be understood that the above description is only exemplary and not in limitation of the invention. We Claim as our invention: a 1. A cast memberycomprisingaftantalurn base alloy 2. Atast member comprising 2 to 10% tungsten, up to 10% rhenium, andthe balance tantalum with incidental amounts of impurities.

a tantalum ba se alloy 7 consisting essentially of by weight 2 to 8% hafnium,

' 3. A cast member comprising a tantalum base alloy consisting essentially of by;weight 210 4% hafnium, 7

15 to 9% tungsten and the balance tantalum with incidental amounts of impurities.

4. A cast member comprising a'tantalum base alloy consisting essentially of by Weight-2% hafnium, 8% tungsten and thetbalance tantalum with incidental. amounts 20 of impurities.

12/58 Austria.

9 DAVID RECK, Primary Exulninerai A K; WINDHAM; ROGER L CAMPBE-LL, WIN- STON A. DOUGLAS, Examiners.

Claims (1)

1. A CAST MEMBER COMPRISING A TANTALUM BASE ALLOY CONSISTING ESSENTIALLY OF BY WEIGHT 2 TO 8% HAFNIUM, 2 TO 10% TUNGSTEN AND THE BALANCE TANTALUM WITH INCIDENTAL AMOUNTS OF IMPURITIES.