US3131059A

US3131059A - Chromium-titanium base alloys resistant to high temperatures

Info

Publication number: US3131059A
Application number: US137723A
Authority: US
Inventors: William T Kaarlela
Original assignee: General Dynamics Corp
Current assignee: General Dynamics Corp
Priority date: 1961-09-13
Filing date: 1961-09-13
Publication date: 1964-04-28
Anticipated expiration: 1981-04-28

Description

United States Patent 3,131,059 CHRUll/HUM-THANIUM BASE ALLGYS RESETANT T0 HEGH TEMPERATWS William T. Ka'arieia, Fort Worth, Tern, assignor to General Dynamics Corporation, San Diego, Calif a corporation of Delaware No Drawing. Filed Sept. 13, 1961, Ser. No. 137,723 17 Claims. (Cl. 75-134) This invention relates in general to alloys capable of resisting high temperatures and more particularly, to alloys of such character well suited for the brazing of columbium and columbium base alloys and having additional utility as high temperature protective coatings and as casting alloys.

It has become increasingly important, particularly in aircraft applications, to use materials which are capable of withstanding extremely high temperatures. One such material is columbium, which is a refractory metal possessing a melting point in the vicinity of 4400 F. From a design standpoint, it is an excellent material because of its high strength to weight ratio in the 2000 to 2500 F. range of service temperatures. It does not strain-harden rapidly, allowing cold working up to 99% without anneal ing, and it is therefore particularly suitable for the forming of parts of complex shape. Columbium is also characterized by moderate density (comparable to iron and nickel), and a high melting point, with good strength retention above the useful range of currently available alloys.

Useful though it is in high temperature areas, joinder of the metal and its alloys presents problems. Thus, although it may be welded, nitrogen contamination is an obstacle since it causes an increase in the tendency for crater cracking, serious loss of ductility and an increase in the transition temperature. Welding also presents the problem of loss of strength due to recrystallization. In the handling of high strength columbium alloys, recrystallization occurs between 2200 and 2800 F., depending upon the alloy makeup. Welding involves these high temperatures and where recrystallization as a result occurs, a loss of approximately 50% in tensile strength may be anticipated.

However, it has been found that by using the alloys of this invention, excellent joinder of the metals is effected and a high temperature resistant joint is produced which is compatible with the strength characteristics of the joined materials. Argon gas is utilized to prevent oxidation of the columbium and its alloys during the brazing, only moderate efforts being necessary for purification of the gas preparatory to brazing.

The alloys of this invention are additionally useful as coatings for columbium and for other materials characterized by low oxidation resistance at elevated temperatures, i.e., of approximately 2000 F.

Further utility for these alloys is found in casting applications and in other areas of metal forming where adequate oxidation resistance at elevated temperatures is difiicult to achieve and maintain and where both structural and non-structural provisions are a requirement.

Accordingly, it is an object of this invention to provide alloys well suited for the brazing of columbium and columbium base alloys, which alloys are capable of providing excellent joint strength at elevated temperatures.

It is another object of this invention to provide alloys of the character described which do not require excessively high temperatures for brazing and which possess adequate ductility.

A further object is to provide alloys, as described, which do not cause excessive erosion of columbium and columbium base alloys when applied thereto in brazing applications.

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Yet a further object is to provide alloys suitable as protective coatings for preventing oxidation of materials having a high susceptibility thereto at elevated temperatures.

Another object is theprovision of alloys adapted to cast- .ing applications which call formaterials possessing adequate oxidation resistance at elevated temperatures.

These and other objects and advantages of this invention will become apparent from the following description of the alloys and their characteristics and the claims directed thereto.

In general the alloys of this invention include as matrix elements chromium and either or both titanium and palladium in the percentage-by-weight ranges indicated. Each of these matrix elements is characterized by its com patibility with columbium and the alloys thereof. An alloying element selected from the group consisting of germanium, vanadium, and gold and proportioned as set forth, is added to the matrix elements. The resulting alloys have produced brazed joints possessing excellent joint strength at high temperatures. This brazing has been effected without the use of extremely high temperatures. Ability of the alloys to withstand high temperatures with a minimum of deterioration has contributed to their further utilization as coatings, protecting against oxidation of materials susceptible thereto. Formability at practicable temperatures and the aforementioned excellent high temperature characteristics further dictate use of the alloys in the area of metal forming, particularly in casting applications. It is to be understood that percentages used herein in the specification and claims to describe ingredient proportions are percentages by Weight unless stated to be otherwise.

Chromium, as an elemental constituent common to each of the alloys has been found to be quite compatible with columbium, forming a diffusion layer which is much like that formed by titanium, but which shows more interaction at the interface with the brazing alloy. As used herein, the general range of chromium is from about 25 to about 65% by weight of the alloy. A preferred range has been found to be from about '35 to about 45%. Superior alloy compositions have been established incorporating the specific proportions of chromium tabulated below.

Titanium has also been found to be a highly satisfactory loy matrix element, being highly compatible with columbium and promoting formation of a narrow diffusion layer at the interface with the columbium. Its general range is from about 10% to about 67% by weight of the alloy. A preferred range is from about 35 to about 45%. Superior alloy compositions have been formulated incorporating titanium in the specific proportions indicated.

Palladium, like chromium and titanium, serves as a matrix element. Like chromium, it has been found to be quite compatible with columbium and forms a narrow alloy layer. It enters into the alloys of this invention in the general range of from about 5 to about 25%. Its preferred range is from about 10 to about 20%. Superior alloy compositions include palladium in the quantities set forth below.

Germanium and vanadium are major alloy elements the general ranges for which are respectively from about 1 to about 20% and from about 5 to about 20%. The preferred proportion for each is about 10%. Germanium shows no obvious harmful effects upon the alloy, its ef fects any in this respect, being masked by other alloy elements. Vanadium shows a distinct inter-granular penetration which is, however, minor. Some solutioning of columbium occurs above 2600 F.

Gold enters into the alloy as an element which pro-, mo c i ter a i t wh h is use nly a a minor element. It has been found to be quite compatible with columbium, forming an alloy layer and causing some solutioning of columbium above 2500 F. when present in a quantity in excess of 10% by weight of the alloy composition. It is helpful in promoting ductility of cera similar phenomenon would be found to exist for each of them.

Numerous high temperature oxidation studies of the above alloys have been conducted. Visual and microtain of the alloys. The range of gold entering into the 5 structural studies indicate the usefulness of these alloys alloys of this invention is from about 1 to about 20%. A as protective coatings for materials having low resistance preferred alloy composition includes about gold. to oxidation at elevated temperatures. Application of Although the process for alloy formulation is subject the alloys may be accomplished by painting or spraying to variation, the alloys of this invention have for test the alloy in powdered form on the surface of the metal purposes been formulated by mixing the elemental in- 10 to be protected and then heating the coated assembly gredients together in the desired proportions in powder until the powdered alloy melts to form a continuous form. The mixture is subsequently br iquetted into a surface coating. Alloys numbers 1, 2, 3, 5, and 6 tabucompact and arc melted in a cold hearth copper crucible. lated above each showed percent weight changes of less If ductile, the alloy is then rolled to form a foil, or than five percent after 100 hours in 2000 F. air, indicatin the alternative, broken into a powder to be used in ing their quality as protective coatings. such form. It is the above qualities of the alloys of this invention As formulated herein, the alloys of this invention have which adapt them for use in metal forming applications. taken the powder form. Application is effected by mix- Quite obviously superior corrosion resistance is offered ing the powder alloy with polyvinyl alcohol in a slurry, at elevated temperatures and with melting points as inwhich is then painted on the joint to be brazed. The alloy dicated, forming is not a problem. The alloys can be is then heated to a temperature above its melting point, made up in the manner indicated above or in other using argon gas for protection against oxidation. As has conventional fashion and then formed. been earlier mentioned, moderate efforts should be made What I claim is: to purify the argon gas. Herein this has been accom- 1. An alloy characterized by' its ability to withstand pl shed satisfactorily by passing the argon through a glasshigh temperatures consisting of by weight from about 35 activated alumina dryer, a -100 F. Dry Ice-acetone to about 65% chromium, from about 20 to about 64% cold trap, and a closed zirconia tube filled with titanium titanium, and from about 6 to about 15% gold. strips and operating at 1750 F. The protection olfered 2. An alloy characterized by its ability to withstand by the argon gas is important. Should atmospheric conhigh temperatures consisting of by weight about 45% tamination occur it will be reflected in reduced flow and chromium, about 45 titanium, and about 10% gold. wetting of the brazing alloy. 3. An alloy characterized by its ability to Withstand For purposes of the tests the results of which are rchigh temperatures consisting of by weight from about fiected in the tabulations below, brazed lap shear test to about 65% chromium, from about 20 to about 64% specimens were made up using for the members to be titanium, and from about 1 to about 15% germanium. joined a columbium alloy incorporating by weight 10% 35 4. An alloy characterized by its ability to withstand titanium and 10% molybdenum. Time at temperature high temperatures consisting of by Weight about 45% prior to testing was 1 minute. Using an A-frarne type of chromium, about 45 titanium, and about 10% gerlap-shear tension test setup, failure was made to occur maniurn. within 1 minute by steadily increasing the mechanical 5. An alloy characterized by its ability to withstand stress upon the specimen by means of a floating screw. high temperatures consisting of by weight from about 35 Stress was measured by means of a load link in conjuncto about 65% chromium, from about 20 to about 60% tion with a strain recorder. Specimens were confined titanium, and from about 5 to about 25% palladium. under a protective argon atmosphere during heating, test- 6, An alloy characterized by its ability to withstand ing, and cooling. high temperatures consisting of by weight from about Each of the alloys of this invention is set out in the 40 to about 45% chromium, from about 40 to about 45% table below with an indication both as to the general titanium, and from about 10 to about 20% palladium. range of its ingredients and as to the specific composition 7. An alloy characterized by its ability to withstand of the particular alloy or alloys tested. Also shown are high temperatures consisting of by weight from about the alloy melting temperatures and the results of shear 25 to'about 40% chromium, from about 20 to about tests conducted at elevated temperatures with regard to titanium, from about 5 to about 20% palladium, each brazed joint. and from about 5 to about 20% vanadium.

Alloy-Gen- Composition, Percent by Weight Melting It. Shear No. eral Range Temp, Strength,

or Specific F. p.s.i. Composition Or Ti Pd Ge V Gold 2,0U0 F 1 {sGcneral 35-65 pec1fic 45 General 35-05 2 lSpeoific 45 Genera 35-65 3 {Specifiann 40 Spec1fie.. 45 4 {grenerahuu 25-49 epee1fic 3o 5 {generaLnn 25-40 pecific 35 G [General 25-40 [Spec1fic 3a During these tests, a remelt temperature rise phenomenon was observed in connection with that alloy designated number 2 in the above tabulation of test results. That is to say the melting temperature of this particular brazing alloy by itself is 2540 F. However, in tests after brazing of the columbium lap shear specimen, it was found that the alloy did not remelt at 3000 F. Al though similar tests were not conducted with respect to the other of the enumerated specimens, it is believed that 8. An alloy characterized by its ability to withstand high temperatures consisting of by Weight about 55% chromium, about 35% titanium, about 20% palladium, and about 10% vanadium.

9. An alloy characterized by its ability to withstand high temperatures consisting of by Weight from about 25 to about 40% chromium, from about 20 to about 65% titanium, from about 5 to about 20% palladium, and from about 5 to about 20% germanium.

10. An alloy characterized by its ability to withstand high temperatures consisting of by Weight about 35% chromium, about 35% titanium, about 20% palladium, and about germanium.

11. An alloy characterized by its ability to withstand high temperatures consisting of by weight from about 25 to about 40% chromium, from about to about 67% titanium, from about 5 to about 25% palladium, and from about 3 to about gold.

12. An alloy characterized by its ability to withstand high temperatures consisting of by Weight about 35% chromium, about 35% titanium, about 20% palladium, and about 10% gold.

13. An alloy characterized by its ability to withstand high temperatures consisting of by weight from about to about 65% chromium, from about 20 to about 67% titanium, and at least one ingredient in the range specified selected from the group consisting of germanium about 1 to about 20%, vanadium about 5 to about 20%, and gold about 6 to about 20%.

14. An alloy characterized by its ability to withstand high temperatures consisting of by weight from about 25 to about 65% chromium, from about to about titanium, and at least one ingredient in the range specified selected from the group consisting of germanium about 1 to about 20%, vanadium about 5 to about 20%, and gold about 6 to about 20%.

15. An alloy characterized by its ability to Withstand high temperatures consisting of by weight from about 35 to about 45 chromium, from about 35 to about 45 titanium, and at least one ingredient in the range specified selected from the group consisting of germanium about 1 to about 20%, vanadium about 5 to about 20%, and gold about 5 to about 20%.

16. An alloy characterized by its ability to withstand high temperatures consisting of by Weight from about 25 to about chromium, at least one ingredient in the range specified selected from the group consisting of titanium about 20 to about 65% and palladium about 20 to about 25%, and at least one ingredient in the range specified selected from the group consisting of germanium about 1 to about 20%, vanadium about 5 to about 20%, and gold from 5 to about 20% 17. An alloy characterized by its ability to withstand high temperatures consisting of by Weight from about 25 to about 65% chromium, from 10 to about 67% titanium, and from about 10 to about 20% palladium.

References Cited in the file of this patent UNITED STATES PATENTS 1,471,326 Copland Oct. 23, 1923 2,169,193 Cornstock Aug. 8, 1939 3,063,835 Stern Nov. 13, 1962 FOREIGN PATENTS 373,725 Germany Apr. 14, 1923 714,820 Germany Dec. 8, 1941

Claims

1. AN ALLOY CHARACTERIZED BY ITS ABILITY TO WITHSTAND HIGH TEMPERATURES CONSISTING OF BY WEIGHT FROM ABOUT 35 TO ABOUT 65% CHROMIUM, FROM ABOUT 20 TO ABOUT 64% TITANIUM, AND FROM ABOUT 6 TO ABOUT 15% GOLD.