US2390805A

US2390805A - Method of making metallic articles

Info

Publication number: US2390805A
Application number: US478642A
Authority: US
Inventors: James A Merryman; Jr Edward M Wharff
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1943-03-10
Filing date: 1943-03-10
Publication date: 1945-12-11
Anticipated expiration: 1962-12-11

Description

1945- J. A. MERRYMAN ETAL 2,390,805

METHOD OF MAKING METALLIC ARTICLES Filed March 10, 1943 WITNESSESI- INVENTORS @"WC' (3 James A. Merry/71cm &

foward M Wharffiur.

0 ATTORNEY Patented Dec. 11, 1945 METHOD OF MAKING METALLIC ARTICLES James A. Merryman and Edward M. Wharif,-Jr., Wilkinsburg, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 10, 1943, Serial No. 478,642

2 Claims.

This invention relates to the method of producing metallic articles.

It is an object of this invention to provide a method of producing strong articles of spray metal.

Another object of this invention is to increase the strength of articles of spray metal without increasing the size of the article.

Other objects of this invention will become a parent from the following description when taken in conjunction with the accompanying drawing, in which:

Figure 1 is a view in elevation of a shaft having a worn end.

Fig. 2 is a view in elevation and partly in section of the shaft of Fig. 1 having spray metal applied thereto in accordance with the teachings of .this invention.

Fig. 3 is an end View in section of the shaft of Fig. 2 with the layers of spray metal carried thereon, V

Fig. 4 is an end view in section of the shaft carrying the spray metal after it has been subjected to a heat treatment in accordance with the teachings of this invention.

Fig. 5 is a view in section of apparatus illustrating the application of the teachings of this invention for the making of articles utilizing a removable form.

Fig. 6 is a photomicrograph at a magnification of 250 times of spray metal steel, and

Fig. 7 is a photomicrograph at a magnification of 250 times of the spray metal of Fig. 6 after having been treated in accordance with the teachings of this invention.

In accordance with this invention, metallic articles are produced by practicing the method of constructing the articles and heat treating them as explained more fully hereinafter. In industry, many metallic articles such as shafts or the like have worn surfaces which render 'such articles unsatisfactory for further service.

Likewise, many castings have pits or flaws therein which render the casting unsatisfactory but which, if filled with a strong bonding metal, can be used commercially.

Referring to Fig. 1 of the drawing, there is illustrated a shaft l0 having a worn end or surface l2. In accordance with this invention, the worn surface 12 is roughened as by knurling or otherwise abrading it after which metal similar to the metal of the shaft lll'is sprayed thereon to deposit a layer M of spray metal of predetermined thickness as illustrated in Figs. 2 and 3.

I2, the spray metal mechanically links or interlocks with the roughened surface and is retained thereon. The spray metal deposit 14 can be readily controlled as to thickness, shape and size, the resulting structure being porous and having an oxide coating'formed on the interlocking portions of the spray metal. When tested, such a deposit of spray metal is found to have only about half of the tensile strength of the solid metal before it is sprayed.

- After the layer Id of spray metal is deposited, the article carrying the spray metal is preferably heat treated in a reducing atmosphere of hydrogen or a mixture of hydrogen and nitrogen or other suitable reducing atmosphere to effect the reduction of the oxides formedduring the spraying of the deposit [4. The lengthof time of heat treating the deposit in the reducing atmosphere to remove the oxides therefrom will vary depending upon the amount of oxides which are present.

When thus heat treated, a suitable brazing metal such as copper, or the well known copper base brazing alloys, or the like, are applied to the oxide-free deposit of spray metal. A preferred method of applying the brazing metal is to spray a layer It of the brazing metal over the external surface of the treated layer I 4. The amount of brazing metal thus applied depends upon the thickness of the layer [4 as will be more apparent from the description given hereinafter.

After the layer I6 of brazing metal is applied to the layer l4, the shaftv l0 carrying the spray metal is admittedto a brazing furnace (not shown) and is heated to a temperature above the melting point of the brazing material but beto applying the layer l6.

low the melting point of the sprayed metal I and the shaft It) in a reducing atmosphere, and maintained at such temperature for a sufficient length of time to permit the brazing material to completely impregnate the layer l4 and bond to the surface I2 of the shaft In as illustrated in Fig. 4. Upon examination it is found that the impregnated layer It is the same as it was prior In other words, the brazing metal does not increase or otherwise change the size of the layer [4 when it fills the pores thereof.

By effecting-the impregnation in a reducing atmosphere, all oxides present in the layers of spray metal are effectively reduced and complete impregnation is obtained if the layer I6 of brazing metal is of a thickness sufficient for supplying enough of the brazing metal for such impregnation. Of course, an excess of brazing metal is a waste remaining on the surface of the layer M or flowing therefrom in the furnace. Any excess of the brazing metal remaining on the surface of the layer I4 can be readily machined Preferably the article is then cooled in the repound as sprayed.

When treated as described hereinbefore and, impregnated with copper, thepsteel has an en- 250 times.

difierent thicknesses of the layer M for obtaining the complete impregnation of the layer l4 and the bonding to the surface I! of the shaft 10.

In another embodiment of this invention, the layer i4 oi spray metal is applied to a' removable form is as illustrated in Fig. 5 ofthe drawing. In this embodiment the form I8 is of graphite or other suitable refractory material, and is designed to have the predetermined shape and size of the article which is to be produced. The layer i4 is readily sprayed onto the form It to any predeterminedthickness and is thereafter treated in a reducing atmosphere to effect the reduction of any oxides. In this embodiment the brazing metal may be applied to thelayer H as by spraying as de'scribed with respect to the embodiment shown in Figs. 1 through 4, or the brazing metallin the form of the pellets 20 or 'thelike may be positioned on the layer ll as illustrated in Fig. 5., The pellets 20 mayv thus be positioned while the coated form is. in the req ducing atmosphere, the temperature of the furnace then being increased to a temperature above the melting point of the brazing metal and maintained at such temperature to insure the complete impregnation of the porous metal layer H.

ducing atmosphere to below 200 C. to prevent the formation of oxides. When thus formed, the impregnated layer ll is readily stripped from the therefrom. By the optimum and minimum thickness of the layer it can be determined for where the sprayed steel is not completely impregnated, a remarkable improvement in strength is obtained, for, in another article in which insumcient copper was employed for-impregnating the sprayed metal, the strength of the'brazed-spray metal increased from one foot-pound to ifootpounds when impregnated even though the article had a porous structure.

form "to give a strong article of required shape and size.

In actual practice, it may be preien'ed to apply a thicker layer-l4 -of the spray metal than is actually required, and after impregnating the layer M with the-brazing metal to machine the impregnatedv layer to the exact. size of the required article. This can readily be' accomplished as the impregnated layer can be as readily ma- I chined as the base metal. Referring to Figs."6 and lot the drawin there is illustrated photomicrographs of sprayed steelof the type 01' the layer l4 and of the same steel after having been impregnated with copper.

Fig.6 in particular is a photomicrograph at a magnification of 250 times of sprayed SAE steel #1010, and clearlyillustrates the eiiect of spraying the steel in that'inipurities are included and the steel is deposited substantially in layers.

Such sprayed steel, when subjected to the Izod impact test, had a strength of only one footutilized as the brazing material completely im- 7 'pregnates the porous structure of the sprayed steel. The impregnated sprayed steel illustrated in Fig. 7 has an Izod impact strength 0150 footthe impregnated sprayed steel over the steelas. sprayed-isremarkable and clearly illustrates the pounda Such improvement in the strength of value of the present invention, similar results being obtained in other sprayed articles.

In general, the impregnation of the sprayed metal layer can b efficiently effected by subjecting the sprayed metal to a temperature of between 1900 and 2100" F. in a reducing atmosphere for a period of time of from 1 to 2 hours to insure the removal of oxides,.'and, after the copper or other brazing material is applied to the oxidefree sprayed metal, subjectingthe article to a temperature of between 2000 and 2300 F. in the reducing atmosphere for a period of time of from 10 minutes to 1% hours, depending upon the size of the article.. I

This invention is particularly applicable to the reclaiming of shafts, tools or-the like which have been damaged in service, or to castings which have pits and flaws or chips therein. The portions of the article which have been rebuilt by applying the spray metal and treated in accordance with this invention have unusual strength and makes it possible to utilize the articles in industry where otherwise they would be normally discarded.

Although this invention has been described with reference to a particular embodiment thereof, it is, of course, not to be limited thereto except in so far as is-necessitated by the scope of the appended claims.

We claim as our invention:

1. The method of making metallic articles comprising, in combination, spraying low carbon steel to deposit and form a. spray metal article having a porous structure, heating the sprayed steel to a temperature of between1900 F. and 2100" F/in a reducing atmosphere for a period of time ranging from one to two hours to reduce anyqoxides present thereon, applying a brazingmetal selected from the group consisting of copper and copper base alloys to the heat treated article, and subjecting the article to a temperature of between 2000' F. and 2300? F. in a reducing atmosphere for a period of time sumcient to permit the brazing metal to penetrate and substantially fill the pores of the sprayed steel.

2. The. method of. making metallic articles comprising, in combination, spraying low carbon steel to deposit and form aspray metal article having a porous structure, heating the sprayed steel to'a temperature of between 1900 F. and 2100 F. in a reducing atmosphere for a period oi. time rangin from one to two hours to reduce any oxides presentthereon, spraying a brazing metal selected from the group consisting of cop per and copper base alloys onto the heat treated sprayed steel, and subjecting the sprayed composite metal to a temperature of between-2000 F.

to penetrate and substantially fill the pores oithe sprayed steel. Y y JAMES A.,MER.RYMAN.

EDWARD M. Jr...