US3043683A

US3043683A - Niobium-titanium chromium alloy

Info

Publication number: US3043683A
Application number: US841683A
Authority: US
Inventors: Hugh B Hix
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1959-09-23
Filing date: 1959-09-23
Publication date: 1962-07-10
Anticipated expiration: 1979-07-10

Description

United States Patent 3,6435% NIQBEUM-TlTANlUM CHROMIUM ALLGY Hugh 3. Hix, Wiimingten, Deb, assignor to E. I. du Pont de Nemonrs and Company, Wilmington, Del., 2 corporation of Delaware No Drawing. Fiied Sept. 23, 1959, Ser. No. 841,68 7 Claims. (Cl. 75-174) This invention pertains to novel niobium base alloys, and more particularly to outstanding high temperature strength and oxidation resistant, ternary alloys containing niobium, titanium, and chromium.

In present-day industry there is an ever-increasing need for metals which are utilizable at very high temperatures. This need has taken on considerable importance as a result of developments in jet engine aircraft and the field of atomic power. high temperature metals are also employed in gas turbines of all types, dies for high temperature working of metals, high temperature reactors, and the like. For a metal to be suitable as a material of construction in high temperature equipment, it must possess, in addition to a high melting point, strength and oxidation resistance at the operating temperatures of the equipment. Furthermore, the metal must be ductile in order to permit its fabrication. It is, therefore, an object of this invention to provide improved, workable alloys which possess unusually high oxidation resistance and strength at elevated temperatures. It is a further object to provide a metal alloy suitable as a material of construction in high temperature equipment of all types.

It has now been found that workable alloys possessing unusually high corrosion resistance and strength at high temperatures can be produced by alloying titanium, chromium, niobium, and the specified optional elements in the amounts set forth herein. It is, therefore, an object of this invention to provide improved, workable alloys which possess unusually high oxidation resistance and strength at elevated temperatures. It is a further object to provide an alloy suitable as a material of construction in high temperature equipment of all types.

' The alloys of this invention comprise niobium base compositions containing about 30% by Weight of titanium, about 130% by weight of chromium, and the balance being essentially niobium in an amount of at least 50% by weight.

In addition to the above-named essential elements, the alloy may contain about 07% of aluminum, about 02% carbon, about 02% cobalt, about 07% iron, about 07% manganese, about 02% nickel, about 02% silicon, about 07% tantalum, about 07% tungsten, about 07% vanadium, about 0-7% zirconium, the sum total of the added elements Al, C, Co, Fe, Mn, Ni, Si, Ta, W, V, and Zr ranging from about 0-7% by Weight. In a more preferred embodiment, the above constituents are in the amounts stated except that the sum total of the optional elements Al, C, Co, Fe, Mn, Ni, Si, Ta, W, V, and Zr ranges fiom about 2-5%.

In another preferred embodiment, the alloys of this invention comprise about 10-25% titanium, about 30% chromium, and the balance being essentially niobium in an amount of at least 50% by weight. In addition, the alloy of this preferred embodiment may contain about 05% of aluminum, about 02% carbon, about 02% cobalt, about 05% iron, about 05% manganese, about O2% nickel, about 02% silicon, about -0-5% tantalum, about 05% tungsten, about 05% vanadium, about 05% zirconium, the sum total'of the added elements Al, C, Co, Fe, Mn, Ni, Si, Ta, W, V, and Zr ranging from about 05% by weight.

In a more preferred embodiment, the alloys of this invention comprise about 15-25% titanium, about In addition to these important uses,v

'ice

28% chromium, and the balance being essentially niobium in an amount-of at least by weight. In addition, the alloy of this embodiment may contain about 0- 5% of aluminum, about 0-2% carbon, about 02% cobalt, about O5% iron, about 0-5% manganese, about O2% nickel, about 0-2% silicon, about 0-5% tantalum, about 0-5% tungsten, about 05% vanadium, about 05% zirconium, the sum total of the added elements Al, C, Co, Fe, Mn, Ni, Si, Ta, W, V, and Zr ranging from about 05% by weight, the balance being niobium in an amount in excess of 50% by weight.

The alloys of this invention may be prepared by conventional metal melting and remelting techniques using inert conditions. The individual metals are melted together, solidified and remelted until homogeneity is obtained. The final melt is then allowed to cool and solidify into a desired shape. The case material thus obtained is of a workable metal with strength and oxidation resistance at high temperatures, and it is suitable as a material of construction in high temperature equipment designed to operate at temperatures beyond the limits of present equipment constructed of the best high temperature alloys.

These new alloys may be prepared in any of a number of types of melting furnaces. The one used in the working examples, 'Which follow, was an arc melting furnace of the type described by W. Kroll in Transactions of the Electrochemical Society, vol. 78, pp. 35-47, 1940. This furnace has an integral, Water-cooled copper crucible in which the charge may be melted and solidified. The charge of metal constitutents for this furnace may be in any convenient form; e.g., powder, shot, wire, sponge, etc. Another suitable melting apparatus is a compressed, consumable arc electrode furnace as described in US. Patent 2,640,860 to S. A. Herres. Also, one may use a combination of non-consumable and consumable electrodes in a double melt furnace such as is described in US. Patent 2,541,764 to the above-mentioned Mr. Herres. A continuous feed furnace such as is described in U.S.P.B. Report 111,083 may also be used. Furthermore, melting could be accomplished by inductively heating the charge in a suitable crucible. Regardless of the melting apparatus used, care should be exercised to protect the molten metals from the normal atmosphere since contamination of the alloy by oxygen, nitrogen, etc. is to be avoided. To prevent this contamination the melting should be carried out under inert conditions, such as an atmosphere of argon or a protective slag or a combination of a protective slag and a controlled atmosphere. The practice of using an inert atmosphere when melting metals is well known in the art.

The following examples are presented to illustrate the preparation of specific alloys of this invention and the outstanding properties of these alloys. These examples are illustrative only and are not to be construed as limiting the invention. All percents set forth in the ensuing examples refer to percents by weight.

EXAMPLE I An alloy of the following composition was prepared: 15 titanium, 23% chromium, 59% niobium, 1% tungsten, and 2% tantalum. The procedure for preparing this alloy was as follows: The individual metal constituents were melted together in a furnace having an integral, water-cooled copper crucible, as described by Kroll in the Transactions of the Electrochemical Society publication referred to above. A helium atmosphere was maintained, and the alloy composition was alternately remelted and solidified six times, whereupon a homogeneous ingot was obtained.

Table I below sets forth the oxidation resistance possessed by the alloy of this example. Oxidation resistance is determined by the following procedure: 7 Weighed samstres at 1200 c. and 1300" c. results or these tests ti -1200 c.

Table I 7 a =P'ercent weight gain Alloy of Example T 1.5 Unalloyed niobium 20 The Rockwell hardness of the alloy was 48.

The ultimate strength for the alloy of Example I is given below and for'purposes of comparison data on good, commercially available alloys are also given:

Psi. Ultimate strength at 200,000

. V V H room temp.

Example I {Ultimate strength at 100, 000 1,150 o. p Ultimate strength at 103,000 l *oom temp. af Alloy N1 20% Ulggianate'strength at 42, 000 Commercial Alloy c: 38% Co, 28% {Ultimate strength at 20,000

512072067 Cr, 7% W, 4% Ti, 2% Fe, 982 0. .ComIIlercialAll0yD:42% Oo,20.5% Ultimate strength at 150,000 Ni, 20% Cr, 4.2% W, 4% Nb, 4% room temp.

Mo, 3% Fe, 1.3% Mn, 0.0% si, Ultimate strength at 50,000 0.4% 0. 871 0.

V BXAMPLE'H An alloy of the following composition'was prepared according to Example I: 22% titanium, 24% chromium, 51% niobium, 1% cobalt, 0.3% silicon, 1.7% tantalum. p

In the oxidation test described in Example 1 this alloy willshow a 0.9% weight gain, as compared with.20% weight gain for unalloyed niobium. The Rockwell hard ness is 49. The'alloy exhibits an ultimate strength of 200,000 psi. at room temperature and 100,O00 p.s.i. at 1150 C. 1 a

. EXAMPLE III Using the procedure 0f Example. I and a charge consisting of 11.2% titanium, 19.2% chromium, and 69.6% niobium, an alloy was made and tested for ultimate strength at room and elevated temperatures.- The following data are the results of the tests and a comparison 1 of such data good,"com'mercially available alloys:

T able II Ultimate Alloy Composition Temperature Strength, p.s.1.

Alloy A (this 69.6% 10.2% Gr, {9 ttgggg invention). 11.2%11. 1601111195 165000 4110 13 80%N1, 20% Cr 421000 Alloy C 38% Go, 28% Ni, 20% 2.O ,000

7 Or, 7% W, 4% Ti, 2% a V Fe,0.2%C.'

Alloy D 42% 00, 20.5% Ni, 20%

. Cr, 4.2% W, 4 Nb, room temp 150,000 4%-Mo, 3% Fe 1.3% 871 0 50,000 M11, 0.6% Si, 0 C.

The room'temperature yield strength of applicants Alloy A at 0.2% offset is 180,000 p.s.i., thus, showing alloy; has useful ductility at room temperature. Ad-

- pare with a standard commercial alloy. at the same elevated temperature, Alloys A and C of Table Hwere formed intof /z cubes andsubjected to compressive Table III shows the 7 Table IV showsacompaxisonof results when Alloys 7 'A and C were subjected torstress at 1300 C.

Table IV Pressure Applied in Pounds/ -Sq. In. AlloyO j AlloyA (this invention) at 1,300" C.' V 7 100,000 p.s.i--...-;. sample crumbledbefore maximum stress was was applies. 110,000psi anvils crumbled 'but 7 there was no upsetin the alloy.

Alloy A in the as cast state was subjected to a force in excess of 300,000 lbs/sq. in. at 1200 C. as reported in Table III. Examination of the microstructure of Alloy A at 250 magnification before it was subjected to the above force showed that it was composed of two phases, the lighter phase being a continuous phase A scratch test made upon the metal by means of a diamond indenter drawn across the surface under constant load did not scratch thecontinuous phase, showing that this is the harder phase. The discontinuous, phase was, however,

scratched, showing it. to. be the softer phase; It is well known in the metallurgical art that fabricability or ductil-ity can be improved if working willconvert the'softerphase into a continuous phase; After subjecting Alloy .A

to the above force, the microstructure of the alloy was again examined at 750smagnification. The working of the .alloy' was found to have. caused the hard continuous phase to be broken into small discontinuous fragments;

It was observed that .the continuous phase the microstructure was the softer phase, thus indicating an improve: ment in the ductility of the metal.

V "EXAMPLE IV V g V A 155 gram ingot of the renewing composition-was prepared: 19.2%. chromium,,,11.2 titanium, and 69.6% niobium, by melting andremelting the metals together 7 ,times in a'water-cooledgcopper crucible of an' arc melting furnace of the type described; by Kroll in the.

. vantaneously, it also appears to exhibit a recrys'talliza:

Transactions of the Electrochemical Society publication referred ,to above. .An atmosphere of helium was used during theheating. When the charge was in the liquid state, the furnace was turned oifpand the melt was allowed" to cool inthe helium atmosphere, When. the ingot reached room temperature, it was removed from the water-cooled crucible and machined into a cube which has proved highly successful as a high temperature forging die.. This alloy has also been made into a high temperature extrusion die. 7 W

- EXAMPLE- V 26.38% by weight er chromium, 14.72% by weight'of 13.38% titanium, 33.11%

5 titanium, and 68.9% by weight of niobium were charged into the furnace of Example I. The metals were heated under an atmosphere of helium until they were liquid. The melt was then allowed to cool under the helium atmosphere; and after room temperature was reached, the ingot formed in the water-cooled crucible was removed. When this alloy was tested for high temperature oxidation resistance in the'manner described for Table I, it showed a 0.65% weight gain over the original as-cast weight of the alloy.

EXAMPLE VI Other outstanding alloys within the scope of this invention made according to the procedures of Example I are as follows:

22% titanium, 5% chromium, 71% niobium, 2% cobalt: After 16 hours exposure to air at 1000 C. in accordance with the procedure described in Example I, the gain in weight in the above alloy based on the as cast Weight of the ingot was 1.4%.

25% titanium, 2.5% chromium, 68% niobium, 2% nickel,

2.5 aluminum: The above alloy after 16 hours exposure to air at 1000 C. in the procedure described in Example I showed a gain in weight of 1.5% based on the as cast weight of the ingot prior to exposure.

10.86% titanium, 32.41% chromium, balance niobium: The above alloy after 16 hours exposure to air at 1000 C. in the procedure described in Example I showed a gainin weight of 0.24% based on the as cast weight of the ingot prior to exposure.

19% titanium, 3% chromium, 72% niobium, 2% nickel, 4% manganese: When this alloy was exposed to air for 16 hours at 100 C. in the manner described in Example I, it showed a 1.55% gain over the as cast Weight of the ingot prior to exposure.

12% titanium, 2.5 chromium, 83.5% niobium, 2%

nickel 25 titanium, 3% chromium, 70% niobium, 2% alumi- 22% titanium, 4% chromium, 70% niobium, 2% nickel,

2% aluminum 5% titanium, 2% chromium, 90% niobium, 0.5% aluminum, 2.5 zirconium 17.60% titanium, 7.23% chromium, balance niobium, R

hardness as cast 47 17.87% titanium, 12.19% R hardness as cast 45 17.79% titanium, 17.40% R hardness as cast 46 chromium, balance niobium,

chromium, balance niobium,

chromium, balance niobium, R hardness as cast 47 16.38% 'tanium, 32.56% R hardness as cast 5 8 12.01% titanium, 26.38% R hardness as cast 55 17.36% titanium, 22.20% R hardness as cast 48 9% titanium, 10% chromium, balance niobium, R hardness as cast 40 25% titanium, 23% chromium, balance niobium, R

hardness as cast 44 10.35% titanium, 33.11% chromium, balance niobium,

R hardness as cast .60

25 titanium, 25 chromium, balance niobium, R

hardness as cast 50 20% titanium, 28% chromium, balance niobium, R

hardness as cast 52 15% titanium, 30% chromium, balance niobium, R

hardness as cast 55 titanium, 7% chromium, balance niobium, R hardness as cast 47 chromium, balance niobium,

chromium, balance niobium,

Although it is preferable to use metals which are of a high purity, a fair amount of variance in purity can be tolerated before product quality suffers appreciably. The alloys of the working examples are made from commercially available metals containingless than 1% incidental impurities. Commercial niobium nearly always contains tantalum (usually in amounts up to 5%) which is hard to detect and very difficult to separate. Therefore, the niobium used to carry out the specific examples no doubt contained tantalum which is reported as niobium rather than as an incidental impurity. In addition to the tantalum which is present in commercial niobium, this invention contemplates the addition of tantalum to the alloy composition in amounts up to 7%. Those skilled in the art are readily aware of the presence of incidental impurities in commercial metals and of the presence of tantalum in commercial niobium, and these facts should be taken into consideration when practicing the invention and construing the claims.

The alloys of this invention may be used as a material of construction in any structure which requires a strong, corrosion-resistant metal. Particular stress has been laid upon the use of these alloys in high temperature equipment, such as jet engine parts, nuclear reactor and gas turbine parts because of their outstanding properties. However, it should be emphasized that use of the alloys of this invention is not limited to high temperature conditions or to any piece of equipment described herein.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited to said details except as set forth in the appended claims.

This application is a continuation-impart of my copending application Serial No. 592,7 05 filed June 4, 1956, now abandoned and also of Serial No. 593,054, filed June 22, 1956, now abandoned. These latter applications are in turn continuations in-part of Serial No. 550,764, filed December 2, 1955, now abandoned.

I claim:

1. A high-strength, corrosion-resistant alloy composed of about 530% by Weight of titanium, about 1-30% by weight of chromium, to which may be added, if desired, up to about 7% by weight of aluminum, up to about 2% by weight of carbon, up to about 2% by weight of cobalt, up to about 7% by Weight of iron, up to about 7% by weight of manganese, up to about 2% by weight of nickel,

up to about 2% by weight of silicon, up to about 7% by weight of tantalum, up to about 7% by weight of tungsten, up to about 7% by weight of vanadium, up to about 7% by weight of zirconium, the sum total of the added elements Al, C, Co, Fe, Mn, Ni, Si, Ta, W, V and Zr ranging up to about 7% by weight, the balance being niobium in an amount of at least 50% by weight.

2. The alloy of claim 1 in which the sum total of the added elements Al, C, Co, Fe, Mn, Ni, Si, Ta, W, V and Zr range from about 25% by weight.

3. The alloy of claim '1 in which the sum total of the added elements Al, C, Co, Fe, Mn, Ni, Si, Ta, W, V and Zr is about 2% by weight.

4. A high strength, corrosion-resistant alloy composed of about 530% by Weight of titanium, about 1-30% by weight of chromium, the balance being essentially niobium in an amount of at least 50% by weight.

5. A high strength, corrosion-resistant alloy composed of about 1025% by weight of titanium, about 1530% by weight of chromium, the balance being essentially niobium in an amount of at least 50% by Weight.

6. A high-strength, corrosion-resistant alloy composed of about 10-25% by Weight of titanium, about 1530% by weight of chromium, to which may be added, if desired, up to about 5% by weight of aluminum, up to about 2% by Weight of carbon, up to about 2% by weight of cobalt, up to about 5% by weight of iron, up to about 5% by weight of manganese, up to about 2% by'weight of nickel, up to about 2% .by weight of silicon, up to about 5% by weight of tantalum, up to about 5% by weight of tungsten, up to about 5% by weight of vanadium, up to about 5% by weight of zirconium, the sum I 7 total; of the added elementsAl, C, Co, Fe, Mn, Ni, Si, Ta, W, V and Zrranging up to about 5% by weight, the balance being niobium in an amount of at least 50% by Weight.

7. A high-strength,corrosion-resistant alloy composed of about 15-25% by weight oftitanium, about 20-28% by weight of chromium, to which may be added, if desired, up to about 5% by weight of aluminum, up to about 2% by weight of carbon, up to about 2% by weight of cobalt, up to about 5% by weight of iron, up to about 5% by weight of manganese, up to about 2% by Weight of nickel, up to about 2% by weight of silicon, up to about 5% by weight of tantalum, up to about 5%, by Weight of tungsten, up to about 5% by weight of vanadium, up to about 5% by weight'of'zirconium, the sum total of the 8 added elements Al, C, Co,'Fe, Mn, Ni, Si','Ta, W, V, and Zr ranging up to about 5% by weight, the balance being niobiumin an amount of at least 5Q% by weight. 1-

References Cited in the tile of this patent UNITED STATES PATENTS 1,588,518 Brace i v June 15, 1926 1,742,417 Schrobsdorfi Ian. 7, 1930 2,822,268 Hix Feb. 4, 1958 2,882,146 Rhodin Apr. 14, 1959 FOREIGN, PATENTS V 7 718,822 Germany Mar. 24,1942

Claims

1. A HIGH-STRENGTH, CORROSION-RESISTANT ALLOY COMPOSED OF ABOUT 5-30% BY WEIGHT OF TITANIUM, ABOUT 1-30% BY WEIGHT OF CHROMIUM, TO WHICH MAY BE ADDED, IF DESIRED, UP TO ABOUT 7% BY WEIGHT OF ALUMINUM, UP TO ABOUT 2% BY WEIGHT OF CARBON, UP TO ABOUT 2% BY WEIGHT OF COBALT, UP TO ABOUT 7% BY WEIGHT OF IRON, UP TO ABOUT 7% BY WEIGHT OF MANGANESE, UP TO ABOUT 2% BY WEIGHT OF NICKEL, UP TO ABOUT 2% WEIGHT OF SILICON, UP TO ABOUT 7% BY WEIGHT OF TANTALUM, UP TO ABOUT 7% BY WEIGHT OF TUNGSTEN, UP TO ABOUT 7% BY WEIGHT OF VANADIUM, UP TO ABOUT 7% BY WEIGHT OF ZIRCONIUM, THE SUM TOTAL OF THE ADDED ELEMENTS, AL, C, CO, FE, MN, NI, SI, TA, W, V, AND ZR RANGING UP TO ABOUT 7% BY WEIGHT, THE BALANCE BEING NIOBIUM IN AN AMOUNT OF AT LEAST 50% BY WEIGHT.