US3035338A

US3035338A - Method of cladding molybdenum

Info

Publication number: US3035338A
Application number: US744352A
Authority: US
Inventors: Iii Harry E Mccune; Remus A Lula
Original assignee: Allegheny Ludlum Steel Corp
Current assignee: Allegheny Ludlum Steel Corp
Priority date: 1958-06-25
Filing date: 1958-06-25
Publication date: 1962-05-22
Anticipated expiration: 1979-05-22

Description

United States Patent Ofilice 3,035,338 Patented May 22, 1082 3,035,338 METHOD OF CLADDING MOLYBDENUM Harry E. McCune Ill, Breckenridge, and Remus A. Lula,

Tarentunl, Pa., asslgnors to Allegheny Ludlum Steel Corporation, Brackenridge, Pa., a corporation of Pennsylvania No Drawing. Filed June 25, 1958, Ser. No. 744,352

6 Claims. (Cl. 29-4715) This invention relates to an improved method of cladding molybdenum and particularly to a method of bonding oxidation resistant nickel and iron base cladding alloys to the surface of molybdenum and molybdenum base alloys.

Material requirements of military and industrial advancement, particularly in the metals field, are demanding metals and alloys with improved high temperature properties. An example of such demand is the necessity to acquire materials with high mechanical properties at temperatures of up to 2000 F. and greater, for uses such as turbine blades for jet aircraft. Molybdenum has been found to be an ideal metal for such applications from a mechanical standpoint. However, molybdenum is a highly reactive metal, the oxide of which is volatile at temperatures of about 900 F. and higher. The oxide ofmolybdenum forms rapidly at these temperatures. For this reason molybdenum may not be employed for such high temperature application except where provision is made to protect the metal against oxidation.

It has long been sought to devise a means to adequately coat molybdenum and alloys of molybdenum with a material that will withstand oxidation at the desired high temperature while permit-ting the molybdenum to provide the required mechanical properties. It is common practice to employ corrosion resistant stainless steels or iron base alloys and corrosion resistant nickel base alloys such as lnconel as cladding for molybdenum. The cladding is generally applied by abrasively cleaning the surfaces of the contacting metals and then forming a box-like structure by placing the cladding on either side of the molybdenum and welding side bars around the sides. he boxlike structure is then evacuated of air and the entire assembly is hot rolled.

Frequently a barrier metal such as chromium plate is applied to the molybdenum core before cladding. This is done to prevent penetration of nickel and iron into the molybdenum as such alloying ingredients tend to lower the recrystallization temperature of molybdenum. Such a barrier metal, however, does not enhance the bonding qualities of the cladding metal.

it has now been found that by employing the method of the present invention a superior bond may be obtained between the cladding metal and the molybdenum.

An object of the present invention is, therefore, to provide a clad molybdenum body that possesses a superior bond between the cladding and the core.

A further object of the present invention is to purposely provide an oxidized surface to the iron or nickel base cladding metal that is placed adjacent to the molybdenum before the ciadding operation is carried out.

Other objects and advantageous features of the present invention relate to the improvement in the bonding of nickel and iron base clad materials to molybdenum which comprises heating said clad materials in an oxidizing atmosphere in order to obtain an oxidized coating on the surface of said clad that is placed adjacent to the molybdenum core prior to hot rolling in order to secure a clad molybdenum structure.

In the practice of the present invention, iron and nickel alloys, and in particular the stainless steels and nickel base alloys, that possess high oxidation resistance at elevated temperatures are purposely provided With an oxide scale before being clad to a molybdenum core. The desired oxide film provided on the cladding metal is the tenacious dark blue or purple scale type in preference to a loose flaky scale. Such an oxide coating may be obtained by heat treatment in air or any oxidizing atmos phere at nearly any temperature above about 600 F., but preferably at a temperature not higher than about 2000 F. The reason such a wide range of temperatures is applicable is that a desired tightly adhering oxide film may be secured at the lower temperatures by merely holding the material at temperature for longer periods of time. However, for practical considerations it is desirable to perform this operation in a time of within one hour. Such metal scale or oxide film may be obtained at the higher temperatures in times as short as one minute. The preferred time and temperatures therefore are from about 600 F. to 2000 F. for from one hour to one minute, the higher temperatures requiring the shorter times and the lower temperature requiring the longer times. Optimum results have been obtained on AIS Type 310 stainless steel and Inco 702 alloy at temperatures of from about 1600 F. to 1650 F. for times of from about five to six minutes. Inco 702 alloy is the designation given by the International Nickel Company of New York, New York to an alloy of the following approximate analysis: carbon about 02%, manganese about 0.10%, iron about 0.35%, nickel about 80.00%, chromium about 15.00%, aluminum about 3.00% and titanium about 0.50%.

The clad surfaces to be bonded need not be abrasively cleaned, but preferably are cleaned of foreign material such as oils, etc., with a solvent such as trichloroethylene. The oxide coated cladding material is bonded to molybdenum or molybdenum alloy in the conventional manner, the cladding material being placed in sandwich fashion on either side of the molybdenum with the oxide film faced inwardly. Side bars are welded around the periphery of the molybdenum in order to form an airtight boxlike construction. A partial vacuum is created in the box before it is heated to a temperature usually of about 2200 F. to be hot rolled to finish gauge. After hot rolling the side bars are generally sheared off in order to provide the molybdenum clad material.

The general procedure for assembling and hot rolling clad materials is as follows:

(1) The core, cladding and side bars are cleaned.

(2) At least one surface of the cladding is heat treated to provide the desired oxide film.

(3) The core is placed in the center of one piece of cladding with the oxide film up and the side bars are placed around the core. The other piece of cladding is placed on top with the oxide film down. The assembly is clamped and welded. A space is retained between the side bars and the cladding for evacuation of air from the assembly. A metal tube is welded into the space to provide a convenient evacuation port.

(4) After welding the assembly is checked for leaks.

(5) The assembly is evacuated at some temperature between room temperature and the hot rolling temperature.

(6) After evacuation the evacuation tube is sealed.

(7) The assembly is hot rolled to gauge and stress relieved.

A good vacuum (less than 25 microns) must be obtained before the assembly is sealed. The evacuation. can

be done at any temperature between room temperature and about 2200 F. At the higher temperatures the time necessary to obtain the desired vacuum will result in ex- ..cessive surface oxidation and a poor hot rolled surface.

At room temperature the metal outgasses very slowly. The evacuation at a moderate temperature, such as 1000 PI, has been satisfactory.

The following specific examples are given to illustrate the present invention and in no way limit the invention to the exact procedure followed.

Molybdenum alloy plates (Moj.5% Ti), approximately .225 ga. x 1 /2" x 1 /2", were clad with Inco 702 alloy and AISI Type 310 stainless steel sheet in both the conventional manner and by the process of the present invention. In carrying out the process of the present invention the cladding metal was oxidized at 1600 F. to 1650 F. for five minutes. Oxide scale was cleaned off one side of the cladding metal.

Cladding was carried out essentially as set forth in steps (1) through (7) above, with the exception that in step (2) the clad metal was not oxidized where conventional practice was followed.

The molybdenum alloy plates were cross hatch ground using emery cloth before cladding. The inside surface of the clad metal employed for the conventional practice was also ground prior to cladding. The side bars employed were made of nickel, while the assembly was welded with a nickel electrode with a single pass all around. Welding was conducted in an argon atmosphere and the assembly was evacuated to create a partial vacuum in the manner described above. A vacuum less than ten microns was employed. Hot rolling to a final hot rolled gauge of .050 inch was accomplished at a temperature of from about 2100 F. to 2200 F. The samples so obtained were then subjected to a peel test. The peel test consists of peeling a small portion of the cladding on one side away from the core, bending the peeled cladding 180 and peeling the cladding away from the core with a tensile machine. The values are reported as the force necessary to separate the cladding from the core for a strip of the rolled product one inch wide. Results are given below in Tables I and II.

It can be seen in Tables I and II that the oxidized clad materials provide a far stronger bond between the cladding and the molybdenum or the cladding and the barrier metal.

We claim:

1. In the production of a clad molybdenum body wherein a first metal selected from the group consisting of molybdenum and molybdenum base alloys is enclosed in a second metal selected from the group consisting of nickel base alloys and iron base alloys, the space between said metals being partially evacuated of air and such structure being hot rolled, the improvement in combination therewith of subjecting the surface of said second metal that faces said first metal to heat treatment so as to produce a tightly adhering oxide film on said surface prior to hot rolling.

2. In the production of a clad molybdenum body wherein a first metal selected from the group consisting of molybdenum and molybdenum base alloys is enclosed in a second metal selected from the group consisting of nickel base alloys and iron base alloys, the space between said metals being partially evacuated of air and such structure being hot rolled, the improvement in combination therewith of subjecting the surface of said second metal that faces said first metal to a temperature of from about 600 F. to about 2000" F. in an oxidizing atmosphere for a time of from one hour to one minute so as to produce a tightly adhering oxide film on said surface prior to hot rolling.

3. In the production of a clad molybdenum body wherein a first metal selected from the group consisting of molybdenum and molybdenum base alloys is enclosed in a second metal selected from the group consisting of nickel base alloys and iron base alloys, the space between said metals being partially evacuated of air and such structure being hot rolled, the improvement in combination therewith of subjecting the surface of said second metal that faces said first metal to a temperature of from about 1600 F. to 1650 F. for a time of from five to six minutes so as to produce a tightly adhering oxide scale on said surface prior to hot rolling.

4. In the production of a clad molybdenum body wherein a first metal selected from the group consisting of molybdenum and molybdenum base alloys is sandwiched between two strips of a second metal selected from the group consisting of nickel base alloys and iron base alloys, side bars are welded to the ends and sides to form a box-shaped structure, a partial vacuum is drawn on the interior of said box-shaped structure and said box-shaped structure is hot rolled, the improvement in combination therewith of subjecting the surface of said second metal that faces said first metal to heat treatment so as to produce a tightly adhering oxide scale on said surface prior to hot rolling.

5 In the production of a clad molybdenum body where in a first metal selected from the group consisting of molybdenum and molybdenum base alloys is sandwiched between two strips of a second metal selected from the group consisting of nickel base alloys and iron base alloys, side bars are welded to the ends and sides to form a box-shaped structure, a vacuum of at least 25 microns is drawn on the interior of said box-shaped structure and said box-shaped structure is hot rolled, the improvement in combination therewith of subjecting the surface of said second metal that faces said first metal to a temperature of from about 600 F. to about 2000 F. in an oxidizing atmosphere for a time of from one hour to one minute so as to produce a tightly adhering oxide film on said surface prior to hot rolling.

6. In the production of a clad molybdenum body wherein a first metal selected from the group consisting of molybdenum and molybdenum base alloys is sandwiched between two strips of a second metal selected from the group consisting of nickel base alloys and iron base alloys, side bars are welded to the ends and'sides to form a box-shaped structure, a vacuum of at least 25 microns is drawn on the interior of said box-shaped structure and said box-shaped structure is hot rolled, the improvement in combination therewith of subjecting the surface of said second metal that faces said first metal to a temperature of from about 1600 F. to 1650 F. in an oxidizing atmosphere for a time of from five to six minutes so as to produce a tightly adhering oxide film on said surface prior to hot rolling.

References Cited in the file of this patent UNITED STATES PATENTS 1,827,297 Moore Oct. 13, 1931 2,707,821 Sowter May 10, 1955 2,763,057 Clair Sept. 18, 1956 2,786,265 Keay Mar. 26, 1957 2,861,327 Bechtold et al. Nov. 25, 1958 2,871,150 Fraser et al. Jan. 27, 1959 2,874,453 Losco et al. Feb. 24, 1959

Claims

1. IN THE PRODUCTION OF A CLAD MOLYBDENUM BODY WHEREIN A FIRST METAL SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM AND MOLYBDENUM BASE ALLOYS IS ENCOLSED IN A SECOND METAL SELECTED FROM TH E GROUP CONSISTING OF NICKEL BASE ALLOYS AND IRON BASE ALLOYS, THE SPACE BETWEEN SAID METALS BEING PARTIALLY EVACUATED OF AIR AND SUCH STRUCTURE BEING HOT ROLLED, THE IMPROVEMENT IN COMBINATION THEREWITH OF SUBJECTING THE SURFACE OF SAID SECOND METAL THAT FACES SAID FIRST METAL TO HEAT TREATEMENT SO AS TO PRODUCE A TIGHTLY ADHERING OXIDE FILM ON SAID SURFACE PRIOR TO HOL ROLLING.