US2373352A - Method of making bearings - Google Patents

Description

April 10, 1945. Q 5 SMART 2,373,352

' METHOD OF MAKING BEARINGS Original Filed Dec. 31, 1957 Cd 'Ni IND/UM 3maentor 62mm aff Patented Apr. 10, 1945 UNITED STATES PATENT OFFICE METHOD OF MAKING BEARINGS Original application December 31, 1937, Serial No.

182,642. Divided and this application September 27, 1941, Serial No. 412,610.

In Great Britain and Canada December 17, 1937 11 Claims.

This application is a division of my copending application Serial No. 182,642 filed December 31, 1937, now Patent No. 2,288,656, dated July '7, 1942. Patent No. 2,288,656 is a continuation-in-part of Paligrit Nos. 2,288,654 and 2,288,655 granted July 7, 2.

The invention herein relates to processes of making bearings and particularly to those which contain cadmium and lead with the purpose of making bearings of these types which are characterized by their resistance to corrosion caused sium and various other alloys of two or more metals including cadmium or lead in the absence of tin. In general, the additional metals added to the cadmium and lead act as hardening and strengthening agents.

I have found, for example, alloys of cadmium and silver to be highly satisfactory for friction surfaces, particularly in the presence of small percentages of additional metals, such as nickel, copper or antimony, which form relatively hard inclusions or particles within the ground mass of the alloy.

The proportion of the ingredients of the cadmium-silver alloy is preferably within the limits of .5-5% silver, .25-1% of a hardening metal or metals and the balance cadmium. More specifically I prefer the composition silver HIS-2.50%, copper, nickel or antimony, separately or in mixtures, .25-.5%, cadmium 97-98%.

One cadmium-copper alloy employed for bearings includes 95-97% cadmium and from 35% of copper. Magnesium u to .5% may be added to this alloy. Another known cadmium-coppermagnesium bearing alloy contains copper .2-1.5%, magnesium .1-.75%, balance cadmium.

The cadmium-nickel bearing alloy ordinarily contains .25-7% nickel and the balance substantially cadmium. Magnesium, zinc, copper, anti mony and aluminum up to 3% may be added to this alloy. It has also been proposed to employ an alloy for bearings composed of cadlmum and magnesium without copper. In this case the magnesium may be present in amount up to 5%. with the balance cadmium.

The cadmium-cobalt bearing alloys consist oi cobalt 15-10% and the balance cadmium.

The alloy known as plastic bronze is an alloy containing a large percentage of lead with the balance approximately all copper, for example, from 30% lead and 70% copper to 50% lead and 50% copper. One analysis of a copper-lead alloy found especially suitable for bearings in accordance with the invention contains approximately 45% lead and copper. Alloys containing other ratios of lead and copper, also may be used as bearing materials,

Cadmium and lead andthe above described alloys thereof, as well as other alloys containing a substantial amount of cadmium or lead, are subject to attack by various acids and other corrosive media. The commercial uses of the copper-lead and cadmium base alloys for bearings, for example, have been retarded due to the corrosive action of acids present in, or formed during the use of certain lubricants. Some lubricants or ingredients thereof, such as lard oil, contain organic acids that tend to corrode cadmium and lead. Other lubricants, for example, some mineral oil lubricants, when subjected to high temperatures, as 275 F. or higher, in the presence of air tend to oxidize to produce acids which have a similar effect. Long life of bearings containing a substantial amount of cadmium or lead may, therefore, be seriously afiected by the presence of such acids, particularly under hard service conditions, such as those that occur in automobile engines.

I have found that corrosion by such organic acids may be substantially prevented by the presence in the alloy or upon its surface of small quantities of, indium. I contemplate the use of the indium either as a constituent in a substantially homogeneous Ialloy with the other constituent or constituents of the bearing or by applying indium to the surface, for example by electrolytic processes. When applied electrolytically it may be desirable to subject the bearing to heat treatment after deposition of the indium thereon to diffuse the indium into the metal or alloy to some extent. Such heat treatment may be carried out, by merely maintaining the hearing, which has been preliminarily coated with metallic indium, at, a temperature below the melting point of the bearing metal or alloybut sufliciently high, e. g., 340500 F. for suflicient time to cause the indium to alloy with the other constituent or constituents to the desired extent. Inthe case of the cadmium or cadmium base alloys the indium is apparently alloyed after a heat treatment the indium is introduced into the hearing by formation of a homogeneous alloy including cadmium from one-tenth of one percent to one percent is found to be sufficient, the amount varying, of course, with the degree of inhibition desired or -the extentto which corrosive acids are present or produced in the lubricant. Larger amounts might, of course, be used but the cost of indium renders it desirable to restrict the content to the amount necessary to eflect the desired inertness to attack by acid products in lubricating oil. In many instances indium within the range .2-.4% has proven sufficient to substantially retard corrosion of cadmium and cadmium base alloys when subjected to corrosive media. such as the acids present in lubricating oils. However, where conditions are quite severe a higher content of indium is preferred. For example, indium within the range .4-.8% substantially prevents corrosion even when the bearing alloy is tested in prepared oils having a much greater corrosive effect than average lubricating'oils after high temperature service.

If, however, the indium is applied to the surface portion only of the cadmium or alloy thereof, the amount required obviously will depend upon the extent of absorption of the indium or the depth of penetration in the cadmium or cadmium alloy. In cases in which it is desired to substantially uniformly diffuse the indium throughout the cadmium or alloy thereof the amount necessary will be comparable with that in which the bearing is originally made from a homogeneous alloy.

When the indium is employed as'a constituent of a homogeneous alloy including cadmium its presence has effects similar in some respects to those produced by silver. It is therefore possible to reduce the silver content of cadmium-silver alloys to some extent while still retaining the desirable hardness and toughness imparted otherwise by a larger silver content. The following may be given as an example of a composition which has been found to have satisfactory properties as a bearing alloy and suitable resistance to corrosion of acids resulting from oxidation of mineral oils:

The remainder substantially cadmium.

The alloy given in this example compares favorably in properties with a similar alloy omitting indium and having 2% or more of silver with the advantage forthe indium containing alloy of greatlyv increased resistance to acid.

Bearing alloys containing a substantial amount of lead ordinarily require a somewhat greater amount of indium than the cadmium base alloys in order to be protected from the eflect of corrosive lubricating oils. For example, with the copper-lead alloys the amount of indium nece's sary may be I within the range .5-8. of the weight of the copper and lead combined. 'Even reater amounts may be used without detrimental effect on the other properties of the alloy, but the is able to use the minimum amount necessary .to

effect the desired result as regards resistance to corrosion.

With the copper-lead alloys it is desirable that the indium be applied first to the surface of the copper-lead, for example by electrodeposition, and then difl'used therein, as by being heated to 340-500" F. for a time interval sufncient to effect the desired diffusion. As an example, a copperlead allo having an electrodeposited coating of indium may be heated to about 340 F. for eighteen hours. The heat treatment is such that a portion atleast of the indium remains on the surface of the copper-lead alloy and forms the bearing surface.

For most purposes a copper-lead alloy facing of approximately -.0l6"-.020" thickness having an electrodeposited coating of indium of from .0001"-.00l" in thickness and heat treated roduces an excellent bearing surface that is highly resistant to the effect of the acids present in or produced during use of certain lubricating oils. In some instances thicknesses of indium slightly less may be employed. considerably greater thicknesses may be used also, but the cost of the indium is such that it is desirable to use the least possible amount necessary to obtain the desired result.

Alloys containing material amounts of tin, as

the usual Babbitt metals, are not liable to attack by the acids occurring in mineral lubricating oils as the tin serves to protect the lead usually present in such alloys. Tin, however, is not used in the so-called "plastic bronze" copper-lead alloys due to the low melting point of the tin-lead eutectic formed, and I have found that tin when added to cadmium in sumcient quantity to exercise the desired protective effect renders the alloy to'o brittle for use in bearings.

As an illustration of the application of my invention to bearings, I have shown in the accompanying drawing a sectional view of a connecting rod bearing comprising a connecting rod 5, a-

sleeve or backing O of relatively hard and strong metal such as steel, or other ferrous metal or alloy, or bronze and a facing I of an alloy of cadmium and silver, with or without a small amount of one or more additional metals, bonded to the surface of the sleeve by an alloy layer 8 containing cadmium and nickel or cadmium and zinc, the facing 1 having at least at the surface a content or coating of indium I. The cadmiumnickel bonding alloy may be composed of nickel from .75-2% with the balance substantially all cadmium. Preferably, the nickel is used in a percentage of around 1%. The cadmium-zinc bonding alloy may contain zinc from 5-20% and cadmium from -95%.

Some difficulty is experienced in satisfactorily bonding a homogeneous cadmium base alloy containing indium to a steel backing. For this reason it is highly desirable to bond the cadmium or cadmium alloy to the steel backing and thereafter apply the indium to. the bearing surface, as by electrodeposition. Thereupon the indium may be diffused into the bearingby heat treatment at a temperature of 3403-1". or higher; In this way the alloy'may be 'readilybonded'to the steel backing.

The cadmium-nickel bondingalloy is greatly preferred since with this alloyfthe bond is not weakened during the subsequent stepOf diffusing the indium into the bearing. For example, I have found that a bearing alloy composed of silver 2.25%, 0.25%. copper and the'balance cadmium may be readily bonded to a steel backing by the use of a cadmium-nickel bonding alloy. Thereupon the bearing surface may be electroplated with the desired amount of indium and heated to a temperature of 340 F. Tests show that strength of the bond apparently is not affected even after holding at this temperature for sixty hours.

In cases in which a copper-lead alloy is used the backing may be of steel or other ferrous metal, or bronze as in the example given with the cadmium base alloy.

In this case the facing I will be of copper-lead having a coating of indiumv thereon as disclosed.

The copper-lead facing may be integrally bonded to the steel backing by being heated to & brazing temperature in a hydrogen atmosphere furnace. Hence, the bonding layer 8 employed with the cadmium base alloys may be dispensed with.

It will be understood that the structure illustrated is merely an example of one use of the invention and is not intended as any limitation on the scope of the invention.

While I have set forth herein specific examples of bearing materials protected against acid attack by the presence of indium, it is not intended to restrict the invention to methods of making bearings of any specific alloy nor any particular amount of indium. I believe that I am the first to have discovered the protecting or inhibiting effect of indium in preventing corrosion due to the organic acids in lubricating oils and particularly those resulting from oxidation of mineral oils at high temperatures, and it is therefore desired to cover such discovery in broad terms.

I claim:

1. The process of making a bearing resistant to attack by acid products in lubricants which comprises forming a backing member of relatively hard and strong metal, securing to said backing member a relatively soft layer of metallic bearing material normally subject to corrosion by acid products in lubricants, electrodepositing a thin coating of indium not greater than about .001" in thickness on said softer metallic bearing material, the amount of the indium being at least .l% of the relatively soft bearing layer, and heat treating the indium and softer metallic bearing material at a temperature of at least 340 F. and below the melting point of the relatively soft layer of metallic bearing material to cause the indium to become diffused into the softer bearing layer to the desired extent thereby producing a bearing in which the said softer metallic bearing material is protected from acid products in lubricants.

2. The process of making a bearing resistant to attack by acid products in lubricants which comprises first forming a bearing backing member of relatively hard and strong metal, and thereafter providing said backing member with a layer of softer metallic bearing material having good anti-frictional properties but corrodible by said acid products and incorporating a small amount of indium in said relatively soft and corrodible metallic bearing material sufllcient to substantially prevent corrosion by said acid products.

3. The process of making a bearing resistant to attack by acid products in lubricants which comprises forming a backing member of relatively hard and strong metal, providing said backing member with a layer of a softer metallic bearing material having good anti-frictional properties but normally subject to corrosion by acid products in lubricants, electrodepositing a thin coating of indium on said layer of softermetallic bearing material, and heat treating the metals under conditions to cause the indium to diffuse into the said layer of softer bearing material to thereby form a bearing in which said softer bearing material is protected from corrosion caused by acid products in lubricants.

4. The process of forming a bearing, the surface portion of which contains a metal of the class consisting of lead and cadmium normally subject to corrosion by acid products in lubricants, which comprises applyin a small amount of indium to the surface of the bearing sufficient to substantially prevent corrosion caused by acid products of oxidation of mineral oils, and thereafter heat treating the metals under conditions to cause the indium to diffuse into the surface portion of the bearing.

5. The process of making a bearing which comprises forming a first layer of relatively hard and strong metal, providing said first layer with a layer containing lead, and thereafter incorporating a small amount of indium in said layer containing lead suflicient to substantially prevent corrosion caused by acid products in lubricants.

6. The process of making a bearing which comprises forming a bearing element having. a facing portion containing lead subject to attack by acid products in lubricants, electrodepositing a thin coating of indium onto the surface of said facing, and thereafter diffusing the coating of indium into said facing to thereby produce a bearing element resistant to corrosion of the lead caused by acid products in lubricants.

'7. The process of making a bearing resistant to corrosion caused by corrosive products in lubricants which comprises forming a backing member of relatively hard and strong metal, providing said backing member with a relatively soft layer of a. metallic bearing material of good anti-frictional characteristics but normally subject to corrosion caused by corrosive products in lubricants, electrodepositing a thin coating of indium onto the relatively soft layer of bearing material, the amount of indium being at least .1% of the relatively soft layer 'of bearing material, and thereafter heat treating the indium coating and relatively soft layer of bearing material at a temperature of about 340-500 F. for a time sufllcient to cause a substantial diffusion of the indium onto the relatively soft layer of bearing material thereby producing a bearing resistant to corrosion caused by corrosive lubricants,

8. The process of making a bearing which in- Q cludes forming a backing member of relatively hard and strong metal, providing said backing member with a layer of softer metallic bearing material having good antifrictional properties but normally subject to attack by corrosive lubricants, electrodepositing onto said softer layer of bearing material a thin layer of indium not greater than about .001" in thickness and at least .1% of the softer layer by weight, and heat treating the indium-coated softer layer at a temperature of about 340-500 F.

9. The process of making a bearing which includes forming a backing member of relatively hard and strong metal, providing said backing member with a layer of soft metallic bearing material having good anti-frictional properties but normally subject to attack by acid lubricants, and electrodepositing onto said soft layer a thin layer of indium not greater than about .001" in thickness and at least .1% of the soft layer by weight.

10. The process 0! iorminz a bearing, the surface portion of which is at least partially formed are metal or the class consisting or lead and cadmium normally subject to corrosion by acid products in lubricants, which comprises electrodepositing a thin layer of indium onto said sur-' face portion, said thin layer being or a thickness not greaterthan about .001" and being at least providing said steel backing member with a relatively soit layer of bearin: material composed essentially of a metal of the class of metals consistim; of cadmium and lead, electrodepositin: a

about .l% of the. weight of the metal of said class thin coating of indium not greater than .001" in thickness on said relatively soft layer, the amount of the indium being at least .1% of the bearing material, and heat treating the indium and said bearing material at a temperature or at least 840 F. and below the meltins point of the said bearing material to cause the indium to become diflused into the bearing material to the desired extent, thereby producing a bearing in which the bearing material is protected from acid products in lubricants.

CLARENCE 1''. SMART.

Images