GB1602785A

GB1602785A - Drill bushing pump seal or similar articles and method of making same

Info

Publication number: GB1602785A
Application number: GB6859/78A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-01-24
Filing date: 1978-02-21
Publication date: 1981-11-18
Also published as: NL7801978A; AU3362778A; BE866585R; SE7802211L; FR2414977A1; CA1070744A; BE864419A; IT1113163B; DE2808680A1; IT7820620A0; JPS54102244A; AU517117B2; CH630154A5

Abstract

This machine element, e.g. a drill bush (121), has a hardened main body (180) made of steel and an approximately 0.1 mm-thick lining (189). The lining (189) is composed of hard particles, such as tungsten carbide particles, which are distributed in a softer matrix, in particular chromium nickel, and bonded to the main body by the latter. The lining (189) is compact or has interspaces for lubricant between the tungsten carbide particles. A base coating of wet binder, which contains chromium nickel powder, and tungsten carbide particles is first of all dried onto the main body (180), the tungsten carbide particles in the wet binder being compacted by rotation or vibration of the workpiece. Binder and a measured quantity of chromium nickel powder are then applied and all the chromium nickel powder is melted at 1050-1110 DEG C with the workpiece rotating or vibrating. In the case of bushes with a small inside diameter, the longitudinal opening (181) of the main body is filled with lining composition and the opening (187) then pierced, by means of an electrode (188) for example. It is advantageous that the wear resistance of the lining corresponds to that of solid tungsten carbide whereas the coefficient of expansion of the machine element itself corresponds to that of steel. <IMAGE>

Description

(54) DRILL BUSHING, PUMP SEAL OR SIMILAR ARTICLES AND METHOD OF MAKING SAME (71) I, EDWARD JOSEPH VOITAS, of 59 De Grav Terrace, Mahwah, New Jersey 07401, United States of America, a citizen of the United States of America, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to articles of manufacture such as drill bushings which are used throughout industry and are commonly incorporated into drill jigs and to the method of manufacturing such articles.

While the principal thrust of the invention is directed toward providing devices which are commonly referred to as drill bushings, it is also within the scope of the invention to provide pump seals, bearings, guide bush ings, spray nozzles and similar articles.

Drin jigs are used to insure the accurate location of a hole, which is to be drilled into a work piece with respect to a fixed reference point or with respect to another hole or pattern of holes. This reference point is used to maintain accurate location of a pattern of holes in the work piece or part which is accurately reproducible over a long production run of such parts. In order to maintain this accurate, small tolerance condition, it is necessary to guide the drills to very close tolerances and to maintain these tolerances throughout the production. This is accomplished by using articles of the invention as drill jig bushings.

The prior art drill jig bushings have been and generally are made of high carbon or alloyed tool steel which have been heat treated to improve hardness. Such bushings provide reasonable drill guidance over their life. The life is relatively short because it is limited by the wear resistance characteristics of the metal. Attempts have been made to improve wear life by using high speed steel of various specialized alloys. These drill jig bushings are much more expensive and leave much to be desired in terms of wear life when they are used, for example, in the drilling of material containing asbestos or other abrasives such as encountered in cast iron.

Alternatively, when log wear life has been the critical element in a production problem, industry has turned to solid tungsten carbide drill bushings. These bushings which are usually solid throughout their crosssection, have several disadvantages. First and foremost, the cost is about 10 to 20 times that of high speed steel. Second, these parts are brittle and are often damaged during installation in the drill jig or are chipped by the tool itself. Various attempts, having limited commercial success, have been made to fabricate a tungsten carbide liner adapted to be pressed or brazed into a steel or other metal body. These units, too, are quite expensive being about 10 to 20 times the cost of tool steel bushings. Moreover, these units which use tungsten carbide fullyinserted bushings or rings brazed, welded or mechanically held in place in a tool or alloy steel body, have sufficient mass of tungsten carbide so that the coefficient of expansion characteristics of tungsten carbide control the expansion of the bushing. Thus, when tool steel tools are used with these bushings, the difference betweeen the coefficient of expansion of the bushing and the coefficent of expansion of the tool, may produce tool seizure. Tool seizure results from the fact that as the tool heats up, its coefficient of expansion is such that it expands at twice the rate of the solid carbide bushing or the one with large inserted masses of tungsten carbide in the form of sleeves or rings. Therefore, initial clearance must be sufficient to avoid this with close tolerance being sacrificed at least during the early period of operation until the tool expands sufficiently to close the excess tolerance. When there are very accurate tool guiding requirements, the tool may be seized and bound after it has been operated for a while.

The production cost of solid tungsten carbide bushings is high because, among other things, the part must be pressed to shape and sintered and then must be ground with a diamond grinding wheel in order to complete the finishing process. Another important disadvantage, which results from the use of solid tungsten carbide is the inability to manufacture drill bushings with a variety of outside shapes. This is inherent in the material characteristics since solid tungsten carbide is difficult to grind and is brittle.

There is thus a need for a method of producing an article, such as a drill bushing or a pump seal, which will maintain its accuracy and possets a longer life than the presently used articles.

Accordingly the present invention provides a method of forming a hollow bushing or similar article which comprises; forming a blank having the desired outer and inner configurations and a central longitudinal axis; cleaning the blank so that it is free of contaminants; forming an adhesive of boric acid dissolved in distilled water and powder of a first material having a hardness in the range of from 59 to 67 Rockwell C; applying the wet adhesive to the inner surface of the blank; adding articles of a second material having a hardness in the range of from 84 to 93 Rockwell C to the wet adhesive so that the wetted surface captures the second material particles; drying the blank at a temperature in the range of from 350" to 400 F for a time sufficient to remove the water and moisture from the blank; adding further wet adhesive to the coated inner surface of the blank; adding first material powder to the wet adhesive on the coated inner surface so that the wetted surface captures the first material powder; drying the blank at a temperature in the range of from 350" to 400"F for a time sufficient to remove the water and moisture from the blank; rotating the blank about the central longitudinal axis after adding the second material particles to the wet adhesive and before drying the blank prior to adding further wet adhesive to the coated inner surface of the blank to induce an outwardly directed force in the range of from 50 to 75 gravities in the second material particles and wet adhesives; raising the temperature of the blank to a temperature in the range of from 1925 to 2025"F; tempering the blank for a time and at a temperature appropriate for treating the body of the blank; and finishing the blank to the desired size and smoothness.

Preferably the first material is nickel chrome and preferably the second material is tungsten carbide.

Such an article will maintain the design clearance between complementary moving parts because the body is steel and the coating whose thickness ranges from .003 to .005 is composed of tungsten carbide particles distributed throughout a matrix of nickel chrome. This allows the coating to have substantially the same coefficient of expan sion as the tool steel body.

Such an article produced according to the method of the invention has a surface with the abrasion and wear resistance of similar articles formed of solid tungsten carbide, is economical to produce and can sell for a fraction of the cost of tungsten carbide drill bushings.

A bushing can be provided which has exposed tool steel at the entering end to thereby avoid tool damage that could occur in the event of an off-center tool came in contact with tungsten carbide of conventional solid tungsten carbide or inserted sleeve or ring type bushings. Beyond the bellmouth or tapered entry side of the drill bushing the thin layer of tungsten carbide provides the highly wear resistant surface.

An article can be produced by a method of the invention whose body is formed of alloy or tool steel and which is provided with a thin coating of tungsten carbide particles which are metallurgically bonded in a matrix of nickel chrome to the body.

In such an article the tungsten carbide particles of controlled micron size may be contained in a matrix of nickel chrome so that the matrix has about the same coefficient of thermal expansion as the body and the drill or rotating shaft inserted in the bushing.

Such an article can have as good or better wear characteristics when compared to solid tungsten carbide articles and also can be less likely to chip or crack in use or during installation.

An article such as a bushing can be provided which has improved lubrication properties because there is produced within the bushing a surface which is unlike a thin solid surface and which has the interstices between the micron size particles of tungsten carbide filled with matrix material. This is accomplished by controlling the amounts of matrix materials sufficient to insure metallurgical bonding to the bushing proper and avoiding filling all the voids or interstices between the particles. Thus, interstices are left for the passage of oil or lubricants between the tungsten carbide particles even while a solid shaft or tool having a close fit is rotated within the bushing.

An article can be provided wherein the inside diameter is lined with a thin coating of tungsten carbide and a controlled amount of matrix which when finished to the proper inside diameter dimension leaves a multipl icity of tool bearing points which are gener ated by the partial cutting of the particles to a condition wherein each particle, so exposed, provides a bearing point while, at the same time, leaving the interstices bet ween particles free to allow lubricant to flow freely.

In such an article the coating of tungsten a carbide . particles can be distributed throughout a matrix of nickel chrome and is dense and relatively void free.

Moreover in such an article the coating of tungsten carbide particles distributed throughout a matrix of nickel chrome can be compacted so as to eliminate entrapped gases or other lightweight foreign material which will be driven from the coating during centrifugal or vibratory compaction.

Additionally in such an article the coating can be placed upon a flat surface to provide a flat, wear-resistant surface on the article.

Broadly, one article produced according to the method of the invention comprises a hollow steel body with various configurations having a coating of a matrix of a material such as nickel chrome added to the inside diameter thereof. Micron size particles of tungsten carbide are uniformly distributed throughout the matrix which provides a metallurgical bond to the steel bod and a metallic bond to each such article. The coating, as applied, has a thickness of the order of between .006" and .008". Final finishing reduces the thickness to the order of approximately .003".

While tungsten carbide particles are preferred, particles of other materials having a hardness in the range of from 84 to 93 Rockwell C may also be used. Similarly, a matrix of material having a hardness in the range of from 59 to 67 Rockwell C may be used in place of the preferred nickel chrome material.

The body and the matrix have about the same coefficients of thermal expansion so that there is little internal strain introduced as the articles heat up from friction during use. Moreover, the article has almost the same coefficient of thermal expansion as that of the drill or shaft which rotates in the hollow opening so that more accurate fitting is initially possible and there is no binding as the temperature rises during use. The term which is normally used to describe the condition, which occurs when the tool expands at a much faster rate than the bushing, is "seized" or "frozen" which indicates metal-to-metal interference. It is also within the contemplation of the invention to provide an article having a surface which has interstices and voids between the particles of tungsten carbide to allow oil, lubricants or coolants to flow freely or be pumped between the inside wall of the bushing and the shaft or tool. Articles made according to the method of the invention avoid freezing or seizing while still maintaining close clearance between tool and bushing.

The method of the invention for producing bushings of .140" diameter or larger broadly comprises applying a thin coating of selected mesh particles of tungsten carbide to the inner longitudinal opening of the body, adhering the particles in place with a suitable adhesive and then applying successive layers of nickel chrome matrix or other suitable alloy and fusing it metallurgically in a vacuum or hydrogen controlled atmosphere or salt bath furnace to allow the matrix material in its liquidus state to fill the interstices between the tungsten carbide particles and also diffusion bonding itself to the inner longitudinal wall or face, as well as providing a bond to the tungsten carbide particles. The body is quenched for heating directly from the fusion stage and annealed.

The body is rotated about its longitudinal axis after applying the tungsten carbide par ticles and again during fusion to compact the tungsten carbide particles and to aid in filling all the voids in the coating.

The inside of the body is rough honed, or ground, then finish honed or lapped to its proper inside diameter. Then the outside of the body is ground to its proper diameter and configuration.

The method of the invention for producing small size bushings differs slightly from that for large bushing. A bushing with a blind hole has adhesive applied to its inner wall, the hole is fully filled with micron size tungsten carbide particles which have been pretreated with a solution of adhesive material which has nickel chrome powder suspended in solution throughout, this insures proper fluxing and bonding to the bushing and of the tungsten carbide to the matrix to be added to the next step. At this step, the cup shaDed portion of the bushing is filled withnicel chrome or other suitable alloy and is treated with adhesive, the article is placed in a vacuum furnace, hydrogen controlled atmosphere furnace or salt bath furnace and when the temperature is brought up to the liquidous state of the matrix material, the excess of matrix material fills the voids and interstices to form a solid plug of tungsten carbide particles, fully bonded to the inner longitudinal wall and to itself. The article is rotated while the matrix is in the liquidus state to induce forces which will aid in filling all the voids in the coating. The body's outside diameter is ground after heat treating and the hole is pierced to an accurate diameter with an electrochemical machine, an electro-discharge machine or a laser beam and is then honed or lapped to its final accurate diameter and surface finish. In the industry, surface finish is designated in units of rms.

The method of the invention for producing pump seals or like articles with flat wear-resistant surfaces is similar to the above-described methods, with the exception that the article is vibrated, rather than rotated, during fusion of the coating to induce forces tending to eliminate voids in the coating.

In the accompanying drawings, forming a part of this application and in which like numerals are employed to designate like parts throughout the same: FIG. 1 is a block diagram showing the steps in a method of forming articles of the invention; FIG. 2 is an elevational view of a simple rotating apparatus employed in the method of FIG. 1, with portions broken away to illustrate component parts; FIG. 3 is an elevational view of a rotating and fusing apparatus employed in the method of FIG. 1, with portions broken away to illustrate component parts; FIG. 4 is a longitudinal cross-sectional view of a flanged blank employed in making an article of the invention; FIG. 5 is a longitudinal cross-sectional view of a straight blank employed in making an article of the invention; HG. 6 is an elevational view of a furnace employed in a method of the invention; FIG. 7 is an enlarged plan view of a fixture employed in connection with the fur nace of FIG. 6; FIG. 8 is a cross-sectional view taken along line 27-27 of FIG. 7; FIG. 9 is a plan view similar to FIG. 7, but showing an alternate use of the fixture; FIG. 10 is a longitudinal cross-sectional view of another article of the invention, in the form of a pump seal; FIG. 11 is an elevational, cross-sectional view of a modified machine; FIG. 12 is an elevational view of a vibrating and fusing apparatus employed in an alternate method of the invention, with portions broken away to illustrate component parts.

FIG. 13 is an enlarged fragmentary elevational view of a portion of G. 12 showing the article being processed; and FIG. 14 is a view similar to FIG. 13, but with the article in an alternate position.

In the drawings, wherein, for the purpose of illustration, are shown various embodiments of the invention, the numeral 230 (Fig. 1) designates the step of forming and cleaning the blank. Step 230 is preferably carried out by machining the part on conventional machine tools. The part must be chemically clean and free of oil, dirt or other contaminants. A preferred method of cleaning is to batch clean the articles in a hydrogen atmosphere furnace. This results in metallurgical cleansing of the articles preparatory to the next step.

After the foregoing procedure has been carried out, boric acid dissolved in distilled water (step 232) and micron size powder of nickel chrome (step 234) are combined to form an adhesive. The adhesive has the consistency of heavy oil. The consistency can be controlled by varying the amount of nickel chrome powder and can be reproduced by accurate control of the ratio of fluid measure to weight of the nickel chrome. Such control insures repetitive consistency of the amount of nickel chrome in suspension. The adhesive so formed is added to the inner surface of the piece (step 236). Next (at step 238), the tungsten carbide particles are supplied to the wet adhesive coated surface.

The tungsten carbide particles are added while the adhesive is still wet so that they are caught in a manner similar to the result obtained when sugar comes in contact with a wet finger. The amount of such adherence will depend on the mesh size of the particles.

Additional steps are provided to increase the density and decrease the porosity of the inner coating of tungsten carbide distributed throughout the matrix of nickel chrome.

After the tungsten carbide particles are applied to the wet adhesive coated surface (step 238) the blank is rotated about its central longitudinal axis to induce about 50 to 75 gravities of force radially outwardly in the coating for about 5 to 7 seconds (step 239). Such centrifugal setting of the tungsten carbide particles while the adhesive is still wet will compact or densify the arti- cles. The piece is now dried (step 2405 at a temperature in the range of from 3500-4000F for a period of time required to bring the part up to uniform temperature and sustained for such time as is required to evaporate all the water and moisture out of the adhesive. To dry articles of the invention on a production basis, the drying (step 240) is done in a conveyor type oven at a temperature in the range of from 3500-4000F. The heating time depends on the mass of the part but the heating time and temperature must be sufficient to insure that all water and moisture is evaporated and removed from the part. Now, the part is cooled to room temperature and the adhesive formed in step 235 is applied over the tungsten carbide layer (step 42). It may be necessary to use one or more coats of adhesive because some of it may be soaked up by the tungsten carbide particles.

At step 244, nickel chrome particles of 140-250 mesh are applied over the wet adhesive. The number of particles which adhere is determined by the amount of adhesive and the mesh size of nickel chrome as the major parameters. The smaller the mesh size, the more solid the coating, so that if a solid coating, free of voids and with filled interstices, is desired, a small mesh size is used. On the other hand, if it is desirable to leave voids and open interstices for lubrication or other operating functions, larger mesh sizes should be used.

The article is now oven dried (step 246) at temperatures in the range of from 350d tc 400"F for the amount of time required : bring the piece up to a predetermined temperature which temperature is sustained until all the water is evaporated out of the adhe sive. Here, again, the drying is carried out in a conveyor type oven at a temperature in the range of from 350C to 400"F for a time which depends on the mass of the article.

The cycle should be sufficient to insure that all water and moisture is evaporated from the part. The part is cooled to room temperature (step 247). When cool it is inspected and any excess particles of tungsten carbide and/or adhesive on the surfaces may be removed with a knife or similar instrument.

Next (step 248) the coating is metallurgically fused to the blank by placing the article in a vacuum furnace, hydrogen atmosphere controlled furnace or in a salt bath furnace.

The coating is metallurgically fused to the blank while the blank again is rotated about its central longitudinal axis to induce about 180 to 200 gravities of force in radially outward direction in the coating (step 248). In this manner, the fused nickel chrome will be urged to fill the interstices between the tungsten carbide particles, thereby tending to eliminate entrapped air, gas, solid particles or boric acid or any other lightweight foreign material and evening out the coating. In the instant method, a positive force is induced within the coating in a direction generally perpendicular to the coated surface to effectively eliminate possible voids.

The temperature of the part is raised to a temperature in the range of from 1925C to 2025"F and the part is held at that temperature, while being rotated, in an appropriate atmosphere. Since rotation increases the speed with which the interstices are filled, the part need to be held at the elevated temperature and simultaneously rotated only for about 30 to 40 seconds.

Subsequently, the part is quenched and tempered (step 249), and then finished by honing or grinding the inside diameter (step 250), grinding the outside diameter (step 251) and finishing the end faces (step 252).

FIG. 2 illustrates a simple rotating fixture for carrying out the centrifugal setting of the tungsten carbide particles (step 239). As seen in FIG. 2, machine 260 includes a frame 262 upon which there is mounted an electric motor 264 having a vertical drive shaft 266. A chuck 268 is carried by the drive shaft 266 for rotation therewith and receives a blank 270 to be processed. A speed control 272 is calibrated to read in terms of the inside diameter of the blank and selects the appropriate speed of rotation of motor 264 to induce the desired 50 to 75 gravities in the coating, for the particular inside diameter of the blank 270 being processed. An automatic start and stop control 274 operates in connection with a brake 276 to activate motor 264 for the prescribed amount of time.

FIG. 3 shows an apparatus for carrying out the step of centrifugal fusing of the coating in blank 270 (step 248). As seen in FIG.

3, apparatus 280 has a frame 282 upon which is mounted an electric motor 284 coupled to a drive shaft 286 through a coupling 288. Drive shaft 286 is journaled for rotation in a bearing block 290 and carries a fitting 292 having a lower mandrel 294 projecting upwardly therefrom. An upper mandrel 296 is carried by a vertical rod 298 and is journaled for rotation relative to rod 298 by means of a bearing arrangement 300.

Rod 298 is a part of a fluid actuator 302 which is mounted on frame 282 and which includes a cylinder 304, and a piston 306 affixed to the rod 298 and movable within the cylinder 304. Fluid, such as air, supplied at passage 308 will raise piston 306 and rod 298 to raise upper mandrel 296 relative to lower mandrel 294. When the upper mandrel 296 is in the raised position, blank 270 can be placed upon the lower mandrel 294. Fluid supplied at passage 310 will then lower the upper mandrel 296 to clamp the blank between the mandrels 294 and z96.

An induction coil 312 is supported by arms 314 movable by an actuator 316 betweeen upper and lower positions. In the upper position of arms 314, as illustrated, induction coil 312 is in position to surround the blank 270 and heat the blank to the desired temperature. In the lower position of arm 314, induction coil 312 is retracted to permit access for loading and unloading blanks 270 between the mandrels 294 and 296.

Actuation of fluid actuator 302 is controlled by control button 320 for enabling loading and unloading of blanks 270. A cycle start control 322 initiates a controlled cycle which places the induction coil 312 in position for heating, activates the induction coil and actuates motor 284 to rotate the blank 270 for a prescribed timed duration. A speed control 324 is calibrated in terms of inside diameter of the blank 270 to enable selection of an appropriate speed of rotation to induce 180 to 200 gravities of force in the coating in the blank. While the blank is rotated and heated, a suitable gaseous mixture such as a mixture of about 95% argon and 5% hydrogen is supplied to a chamber 326 through a solenoid operated control valve 328. The gaseous mixture flows from chamber 326 through a conduit 400 in rod 298 to an upper passage 402 through upper mandrel 296 and into the blank 270. The gaseous mixture fills the blank 270 and proceeds through a lower passage 404 to exhaust ducts 406 in fitting 292. Exhaust ducts 406 direct the gaseous mixture upwardly toward the blank 270 along the exterior of the blank. Thus, the appropriate inert atmosphere is provided during rotation of the blank and fusing of the coating within the blank. A further control 408 is provided for any emergency stop of the cycle of operation.

FIG. 4 illustrates a blank 270 having a construction suited to the method depicted in FIG. 1. Blank 270 has a body 410, a head 412 and a coating 413 made up of a matrix of nickel chrome throughout which are distributed particles of tungsten carbide to be fused to the inner surface of the body 410 and a portion of the inner surface of the head 4 412. Blank 270 is employed in making a drill bushing and has a longitudinal length greater than the finished drill bushing by an added head portion 414, which extends axially outwardly beyond line 416 and an added body Portion 418, which extends axially outwardly beyond line 420. Portions 414 and 418 extend radially inwardly beyond the coating 413 and provide dams at 422 and 424 to contain the materials of the coating 413 during rotation of the blank 270 about longitudinal axis L while the coating 413 is fused. A chamfer 426 at each end of the blank 270 enables proper seating of the upper and lower mandrels 294 and 296 of the apparatus 280.

In order to finish the blank 270 to construct a drill bushing, the portions 414 and 418 are removed, as by grinding the ends of the blank 270 down to the lines 416 and 420 and providing a radius at edge 428 (step 252), leaving a finished drill bushing. When bushings of this type are used, there is virtually no wear on the steel forming the head or top of the bushing, the body proper being contained in the drill jig, fixture, etc., but it is recognised that the bell mouth being coated with wear resistant tungsten carbide can damage the cuttting edge of a tool formed of high speed steel if the tool enters off centre. Consequently, in some operations this coating of the bell mouth is undesirable.

Figure 5 illustrates another blank 430 for constructing a straight drill bushing. Blank 430 has a body 432 and a coating 434 along an inner surface of the body. Portions 436 and 438 extend outwardly beyond lines 440 and 442, respectively, and establish dams at 444 and 446 for containing the fused coating during rotation of the blank about longitudinal axis LL. Portions 436 and 438 are removed, subsequently, down to lines 440 and 442, and a radius is provided at edge 448 to complete the straight drill bushing.

The matrix is of tungsten carbide and nickel chrome fused to the inner surface and to a portion of the upper surface. This type of bushing, in general, is a headless type and is used where the working surface must be flat and clear of projections and the bushing must present a flat unobstructed surface, Here again, it may be desirable to utilize an uncoated bell mouth to reduce tool wear.

Figure 6 illustrates a furnace 450 for carrying out the step of fusing while rotating (step 248) either larger blanks such as those used for drill bushings having an inside diameter of 1 3/4" or over, or batches of small b small blanks used for small bushings having a blind hole, cylindrical insert 502 is removed and is replaced by two or more opposed wedge-shaped inserts 504, also constructed of ceramic, graphite or another refractory material, as seen in FIG. 9.

Inserts 504 are supported and captured between adjacent ribs 506 of the fixture 460 and each includes a plurality of horizontally oriented openings 508 for receiving small blanks 510 which are then rotated with fixture 460, while being heated, to induce forces urging the fused mixture within the blanks 510 toward the bottom of the blind hole in each blank, thereby compacting the tungsten carbide particles within the matrix of nickel chrome and eliminating all voids while expelling entrapped gas and lightweight foreign materials.

FIG. 10 shows a pump seal 520 constructed in accordance with the invention.

Pump seal 520 includes a steel body 522 having a generally cylindrical configuration including a flange 524 at one end thereof.

The end faces 526 and 528 each have a respective annular recess 530 and 532 and each recess is filled respectively with a coating 534 and 536 of tungsten carbide particles distributed throughout a matrix of nickel chrome, the coatings providing wearresistant liners and resembling the coatings described in connection with the bushings illustrated above. The liners provided by coatings 534 and 536 enable maintenance of the accurate location of an abutting, relatively moving element as the surfaces of the moving element and the liners continue to move relative to one another.

The basic method for making the pump seal 520 resembles the above-described methods for making bushings insofar as concerns the formation of a pump seal blank 538 (see FIG. 11) and the placing of the adhesive and tungsten carbide particles within the recesses of the blank. However, in order to eliminate voids within the coatings 534 and 536 an alternative is employed in place of the application of centrifugal force during fusion of the coatings. Instead, each coating is fused while being vibrated preferably in directions parallel to the central longitudinal axis P of the blank 538.

Thus, in the method for making pump seal 520, the initial steps are very much the same as steps 232 through 247 shown in FIG. 1, and apparatus similar to that of FIG.

3 can be employed to fill each recess 530 and 532, one at a time. The apparatus of FIG. 11 has a sleeve 540 with inside dimensions suited to the support of the blank 538 for pump seal 520, all as shown in FIG. 11.

The apparatus is re-oriented so that the blank 538 is supported with its central longitudinal axis P extending in a vertical direction, as seen in FIG. 11. Sleeve 540 has a larger bore 542 with an inside diameter complementary to the diameter of flange 524 and a smaller bore 544 with an inside diameter complementary to the diameter of the other end of body 522. Hence, pump seal blank 538 may be seated in sleeve 540 with either recess 530 or 532 facing upwardly to receive a deposit of particles and adhesive.

Once one recess 530 is filled with the appropriate coating with all of steps 232 through 247 having been performed to fill recess 530, pump seal blank 538 is placed in a vibrating apparatus for simultaneous fusion of the coating within recess 530 and vibration of the blank 538 preferably in vertical directions, parallel to the central longitudinal axis P of the blank 538 and generally perpendicular to the recess 530. As seen in FIG. 12, blank 538 is placed in apparatus 550 which includes a stationary frame 552 supporting a hood 554 seated within a sand sea 556 to establish a closed chamber 558.

Hood 554 may be lifted from frame 552 to gain access to chamber 558. As in the earlier-described arrangements, an inert gaseous mixture such as a mixture of argon and hydrogen is supplied through a supply line 560 to establish an appropriate atmosphere within closed chamber 558, while purging the chamber through purge line 561.

As best seen in FIG. 13, as well as in mG.

12, blank 538 is placed within a support ring 562 secured to a platform 564 carried by a sub-frame 566 having posts 568 passing through dynamic seals 570 in frame 552. A suspension system 572 supports the subframe 566 on the stationary frame 522 and includes opposed helical springs 574 which permit upward and downward movement of the sub-frame 566 relative to the stationary frame 522. An air-driven vibrator 576 is coupled to the sub-frame 566 for vibrating the sub-frame in a vertical direction through a typical amplitude of about 0.0005 to 0.001 inch at a rate of about 16,000 to 20,000 cycles per minutes.

When sub-frame 566 is vibrated, blank 538 will be vibrated with the sub-frame. At the same time, an induction coil 578, located immediately above the coating in recess 530 of blank 538 is activated to heat the blank 538 locally and fuse the coating in recess 530. Power is provided to induction coil 578 through a first fitting 580, while cooling water is provided for coil 578 through further fitting 582. Vibration and heating are continued simultaneously for about 30 to 90 seconds to attain complete fusion, the filling of voids and expulsion of gases and other lightweight foreign materials.

The entire procedure is repeated for establishing the fused coating 536 in recess 532; that is, the blank 538 is again placed in sleeve 540 in a modified machine of Figure 11, but with recess 532 facing upwardly.

Once recess 532 is filled, blank 538 is transferred to ring 562 of apparatus 550, but with ring 562 inverted and recess 532 facing upwardly as seen in FIG. 14. The blank again is subjected to vibration while the coating 536 is fused in recess 532. It is noted that since the induction coil 578 effects only local heating, fusion of coating 536 will not cause coating 534 to be fused again. Upon completion of the step of fusing while vibrating to complete coating 536, the blank 538 is removed from apparatus 550 to be quenched, tempered and finished to establish pump seal 520. Thus, the step of vibrating while fusing serves to establish improved wear-resistant coatings having flat surfaces for component parts in which such flat surfaces are desired.

Having regard to Section 9 of the Patents Act 1949 reference is directed to the claims of Specification No. 35684/79 (No.

1 602 786).

WHAT I CLAIM IS: 1. A method of forming a hollow bushing or similar article which comprises; forming a blank having the desired outer and inner configurations and a central longitudinal axis; cleaning the blank so that it is free of contaminants; forming an adhesive of boric acid dissolved in distilled water and powder of a first material having a hardness in the range of from 59 to 67 Rockwell C; applying the wet adhesive to the inner surface of the blank; adding particles of a second material having a hardness in the range of from 84 to 93 Rockwell C to the wet adhesive so that the wetted surface captures the second material particules; drying the blank at a temperature in the range of from 3500 to 4000F for a time sufficient to remove the water and moisture from the blank; adding further wet adhesive to the coated inner surface of the blank; adding first material powder to the wet adhesive on the coated inner surface so that the wetted surface captures the first material powder; drying the blank at a temperature in the range of from 350 350" to 400 F for a time sufficient sufficient to remove the water and moisture from the blank; rotating the blank about the central longitudinal axis after adding the second material particles to the wet adhesive and before drying the blank prior to adding further wet adhesive to the coated inner surface of the blank to induce an outwardly directed force in the range of from 50 to 75 gravities in the second material particles and wet adhesive; raising the temperature of the blank to a temperature in the range of from 1925C to 20250F; tempering the blank for a time and at a temperature appropriate for treating the body of the blank; and finishing the blank to the desired size and smoothness.

2. A method according to claim 1, including rotating the blank about the central longitudinal axis while the blank is held at the temperature in the range of from 19250 to 20250F for a period of 30 to 40 seconds to induce an outwardly directed force in the range of from 1 0 to 200 gravities in the first and second material coated on the inner surface.

3. A method of forming a hollow drill bushing or similar article which comprises; forming a blank having the desired outer configuration; cleaning the blank so that it is free of contaminants; drilling a blind longitudinal opening in the blank; forming an adhesive of boric acid dissolved in distilled water and powder of a first material having a hardness in the range of from 59 to 67 Rockwell C; applying the adhesive to the surface of the longitudinal opening; precoating particles of a second material having a hardness in the range of from 84 to 93 Rockwell C with the adhesive; filling the longitudinal opening with the precoated second material particles; drying the blank at a temperature in the range of from 350" to 4000F for a time sufficient to remove the water and moisture from the blank; adding adhesive to the longitudinal opening; adding a measured amount of first material particles at the top of the longitudinal opening; drying the bLank at a temperature in the range of from 350" to 4000F for a time sufficient to remove the water and moisture from the blank; raising the temperature of the blank to a temperature in the range of from 19250 to 20250F; rotating the blank while the blank is held at the temperature in the range of from 1925 to 20250F for a period of 30 to 40 seconds to induce a force in the range of from 180 to 200 gravities in the first and second material in the opening, tempering the blank for a time and at a temperature appropriate for treating the body of the blank; removing the top and bottom of the blank to thereby expose the ends of the filled longitudinal opening; piercing an opening through the filling longitudinal opening; finishing the blank to the desired size and smoothness.

4. A method of forming a wear-resistant liner on a bushing, a seal or a similar article, including; forming a blank having a surface which will receive the wear-resistant liner; cleaning at least said surface of the blank so that the surface is free of contaminants; forming a wet adhesive which includes powder of a first material having a hardness in the range of from 59 to 67 Rockwell C applying the wet adhesive to said surface r1 the blank; adding particles of a second rnaterial having a hardness in the range of from 84 to 93 Rockwell C to the adhesive; com

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 532; that is, the blank 538 is again placed in sleeve 540 in a modified machine of Figure 11, but with recess 532 facing upwardly. Once recess 532 is filled, blank 538 is transferred to ring 562 of apparatus 550, but with ring 562 inverted and recess 532 facing upwardly as seen in FIG. 14. The blank again is subjected to vibration while the coating 536 is fused in recess 532. It is noted that since the induction coil 578 effects only local heating, fusion of coating 536 will not cause coating 534 to be fused again. Upon completion of the step of fusing while vibrating to complete coating 536, the blank 538 is removed from apparatus 550 to be quenched, tempered and finished to establish pump seal 520. Thus, the step of vibrating while fusing serves to establish improved wear-resistant coatings having flat surfaces for component parts in which such flat surfaces are desired. Having regard to Section 9 of the Patents Act 1949 reference is directed to the claims of Specification No. 35684/79 (No.

1 602 786).

pacting the second material particles; drying the adhesive and the second material particles added thereto to establish an initial coating on said surface; adding further wet adhesive to the initially coated surface; adding first material powder to the further wet adhesive; drying the further wet adhesive and the first material powder added thereto to establish a complete coating on said surface; raising the temperature of the blank at said surface to a temperature in the range of from 1925C to 202SF, holding the blank at said temperature to fuse the first material and bond the second material particles in a liner adhered to said surface, and inducing a force in the complete coating while holding the blank at said temperature, the force being induced by rotating or vib- rating the blank and tending to eliminate voids in the coating and expel unwanted foreign material.

5. A method according to claim 4, - wherein said force extends from the complete coating toward said surface and is generally perpendicular to said surface.

6. A method according to any one of claims 1 to 5, wherein the first material is nickel chrome.

7. A method according to any one of claims 1 to 6, wherein the second material is tungsten carbide.

8. An article of manufacture for accurately locating abutting relatively moving surfaces, one of which surfaces is on the article of manufacture and the other of which surfaces is on an abutting element, produced according to the method of claim 1, claim 3 or claim 4, said article comprising; a body formed of a relatively rigid material, such as steel, and having a recess therein; a liner of particles having a hardness in the range of from 84 to 93 Rockwell C in a matrix of material having a hardness in the range of from 59 to 67 Rockwell C bonded to at least a portion of said recess in the body and having said one of the surfaces thereon to receive the abutting moving surface of the abutting element; the liner being such that the liner and the body together have a coefficient of thermal expansion substantially equal to that of the abutting element to thereby accurately maintain the abutting location of the moving surfaces.

9. An article according to claim 8, wherein the particles of material having a hardness in the range of from 84 to 93 Rockwell C are tungsten carbide.

10. An article according to claim 8, wherein the matrix of material having a hardness in the range of from 59 to 67 Rockwell C is nickel chrome.

11. An article according to any one of claims 8 to 10, wherein the moving surfaces are substantially flat.

12. A method of forming a hollow bushing or a wear resistant liner on a bushing, according to claim 1, claim 3 or claim 4, substantially as hereinbefore described with reference to the accompanying drawings.

13. An article produced according to the method of claim 1, claim 3 or claim 4, substantially as herein before described with reference to the accompanying drawings.