US3389981A - Method of bonding diamond and metal - Google Patents

Description

June 1968 H. L. STRAUSS, JR

METHOD OF BONDING DIAMOND AND METAL Filed Oct. 8, 1963 FIG.

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United States Patent Ofice 3,339,981 Patented June 25, 1968 3,389,981 METHOD OF BONDING DIAMOND AND METAL Harry L. Strauss, Jr., 183 Sterling Road, Harrison, N.Y. 10528 Filed Oct. 8, 1963, Ser. No. 314,720 Claims. ((31. 51293) This invention relates to the bonding of diamond and metal, and more particularly to the manufacture of abrasive tools using diamond grit or pieces.

In some tools diamond grit may be distributed through a body of matrix material, and in other cases using somewhat larger pieces, the diamonds may be localized at the surface of the tool. One example is a dressing tool having diamond grit for dressing abrasive wheels using silicon carbide, aluminum oxide or other such abrasive. The dressing tool may be a rod or a wheel. A wheel having diamond grit may itself be used as an abrasive wheel. Another example would be a core bit for drilling for earth exploration, in which a tubular matrix with diamonds embedded in its lower edge is used.

Ditferent processes have been used, including casting metal around the diamonds, which is bad because of oxide between the metal and diamond which is injurious to the bond. Souventional brazing has been used, but this needs flux to wet both metal and diamond, and the flux detracts from the bond. Hydrogen brazing is better than in air, but is very expensive because of equipment needed, and it is difiicult to obtain uniform results. There is also danger of hydrogen explosion.

Sintered metal powder has been used. In one system the sintering is done in a hydrogen atmosphere, but this raises all of the hydrogen problems already mentioned. In another system there is sintering in air, using a hot press, but this again forms oxides. Sintering with a hot press in a vacuum, or in hydrogen, has been suggested, but again complex equipment is needed and difiiculties arise.

The primary object of the present invention is to overcome the foregoing difficulties, and to generally improve the manufacture of diamond tools of the described class. Another object is to provide a process which results in a greatly improved diamond tool by achieving a true metal to diamond bond, which holds the diamond with maximum strength. There is also a better metal to metal bond. In both cases there is probably a better wetting action.

To accomplish the foregoing general objects, and other more specific objects which will hereinafter appear, my invention resides in the process steps, and their relation one to another, as are hereinafter more particularly described in the following specification. The specification is accompanied by drawings in which:

FIG. 1 is a front elevation of a dressing or abrasive wheel;

FIG. 2 is a section through the same;

FIG. 3 is a schematic transverse section through a treatment chamber used in practicing the invention; and

FIG. 4 is a schematic perspective view showing the treatment chamber connected to high vacuum apparatus.

Referring to the drawing, and more particularly to FIGS. 1 and 2, the particular tool here being made is a small dressing orabrasive wheel 12, using diamond grit in a matrix of sintered metal. However, as explained above, the tool may take a variety of forms depending on the purpose for which it is intended.

In accordance with known practice, the mixture preliminarily is compressed under sufiicient pressure to give it some green strength, so that the embryo product may be more conveniently handled.

Referring now to FIG. 4 of the drawing, there is ahigh vacuum chamber 14, which in this case is cylindrical and has a hinged door 16 at one end. Appropriate gaskets are provided to permit exhaustion to a high vacuum. The vacuum may be produced by any known controlled high vacuum apparatus, indicated in somewhat simplified or schematic form at 18 and 20, the connection tochamber 14 being through a relativelylarge diameter pipe 22. Aram 24 projects downwardly through the wall of the vacuum chamber, and is actuated by a press which is not shown. The use ofram 24 is optional, and when it is employed, it passes through elaborate seals of known character so as not to prevent high vacuum in the chamber.

Referring now to FIG. 3 of the drawing, thechamber 14 andram 24 correspond to those previously mentioned. The chamber rests on abase 26, which in turn rests on the bed of the press (not shown) which actuates theram 24. Thechamber 14 includes a table 28 having a pedestal 34) on which the embryo product may be carried, this being indicated at 12. The product includes a metal hydride, for release of hydrogen during the process. Thechamber 14 has means to heat the product to a high temperature, and in the present case the heat is provided by aninduction heating coil 32 which may be of conventional character. Usually it has turns of copper tubing which carry water for cooling. The coil could be movable, but more simply may be fixed in location but so dimensioned as to afford easy access to the product being treated. Thevacuum chamber 14 is further arranged for very rapid cooling by refrigeration, and for this purpose, the chamber is lined with refrigerator coils indicated at 36. It will be understood that theinduction heating coil 32 is connected through suitable leads or pipes to a source of electrical power, not shown, and thecoils 36 are connected through pipes 38 to suitable refrigerating equipment, not shown.

While not essential, it is preferred to treat theproduct 12 under direct mechanical pressure at the same time that it is being subjected to environmental vacuum, and for this purpose the product may be placed in a bottom mold 411, and enclosed by atop mold 42, the latter receiving the force ofram 24 when the ram is lowered. The ram is retractable for a substantial distance to facilitate insertion or removal of the mold, and/or the product being treated.

The chamber preferably has a temperature-sensitive device 44 which leads throughconnection 46 to a temperature indicator, and a pressure-sensitive device 48 which leads throughconnection 50 to a vacuum indicator.

The vacuum chamber is further provided with a small crucible 52 in which a suitable getter is placed. For the particular procedure hereinafter described, the getter is preferably small chips of titanium, or small pieces of titanium wire, indicated at 54. The amount of titanium getter may be about two percent of the matrix material being treated.

The metal powder mixture in the matrix, 32 may contain some or all of iron, copper, tin. nickel, cobalt, chromium boride, tungsten carbide, and titanium hydride. The constituents may vary, and also the proportions used may vary.

Titanium hydride or some metal hydride is highly important in the mixture because it releases hydrogen. which is valuable as a reducing agent and to help the vacuum remove contaminants. In one theory, the pure titanium getter in the crucible adsorbs hydrogen and then exchanges it for other contaminants at an elevated temperature. Most of the contaminants and hydrogen are removed by the vacuum, and the getter improves the operation of the apparatus.

The present invention may be considered to be empirical, and I do not wish to be limited to or to be bound by this or other theoretical observations in this description.

The process of manufacture includes subjecting the product to heat and to environmental vacuum until the temperature has risen high enough and the treatment is continued long enough for the release and removal of hydrogen and impurities, and for bonding of the metal, whereupon the heating is replaced by abrupt cooling by actual refrigeration until the product is cooled to room temperature. It is possible that this form of quench action produces a precipitation hardening of the metal. In any case the result is an improved product. During this cooling the environmental vacuum is maintained. The temperature to which the product is raised is preferably in a range of from 1800 to 2400. The vacuum is preferably carried down to about 10- or microns of mercury. The treatment is continued for a period of about six to ten minutes, but preferably in several stages, as is described later.

In preferred method, the product is subjected to direct mechanical pressure during the treatment described above. When this is to be done it is not essential to previously cold compress the material for green strength as mentioned above. However it is still convenient and desirable to do so.

As mentioned, the treatment is preferably divided into stages, and in the first stage the temperature may be raised to above 800 F., and the product is treated at that temperature for several minutes, say three to five minutes. Hydrogen is released from titanium hydride at about 700 F., and it is desired to safely reach that temperature. Then the heating may be resumed to raise the temperature to a range of from 1800 to 2400 F, and

the product then is treated at the said elevated temperature for several minutes, say three to five minutes.

Considering the preferred process in greater detail, the vacuum apparatus and the heater may be operated and the temperature raised to a range of 400 to 500 F. Active evacuation is then interrupted, while continuing heating to a temperature of say 800 F., at which point the existing conditions are maintained for several minutes, say three to five minutes, as mentioned above. The operation of the heater is resumed to raise the temperature to a range of 1800 to 2300 F. During this time active evacuation is resumed down to a vacuum of about 10- or 10- microns of mercury, but the restart of the vacuum apparatus may be delayed, but if delayed it should be started at latest when the temperature has reached 1600 F.

The final temperature selected depends on whether the metal matrix is made of a soft or hard metal, the lower temperature (say 1800 F.) being used for softer metals, and the higher temperature (say 2300 F.) being used for harder metals. By hard metal is meant metals such as tungsten carbide, or chromium bon'de or other borides with suitable cementing metals. By soft metal is meant nickel bearing brasses, or copper alloys.

The elevated temperature is maintained for a period of several minutes, say three to five minutes, this being the second treatment stage. During this time the vacuum apparatus may be stopped or not, depending on the alloy being treated, and the getter being used. The temperature then may be momentarily raised a little, say F. higher, but this is not essential.

The energization of the induction coil then is stopped, and refrigeration is applied to the refrigerating coils for abrupt cooling. Here again there is preferably a difference in procedure as between hard and soft metals. In the case of hard metals, the vacuum apparatus, if stopped during the second stage dwell, now is started and operates throughout the refrigeration or rapid cooling period. In the case of soft metals the starting of the vacuum apparatus is delayed until the temperature has dropped to about 900 F. and is then started. In either case (hard or soft metals) the active evacuation is applied during the continued rapid cooling or refrigeration below 900 F. and on down to room temperature.

Both the vacuum apparatus and the refrigerator are stopped before opening the vacuum chamber door, and the ram is raised for removal of the finished product.

When mechanical pressure is applied by means of a ram during treatment, as here shown, the mold parts are designed to withstand the high temperature, and also the abrupt drop in temperature caused by refrigeration. The mold 40 andring 42 constituting the mold are preferably made of carbon, but may be made of a refractory material, or of stainless steel. Carbon is preferably used when the sintered metal is one which is rather nonresponsive to induction heating. The carbon then heats up and transfers heat to the product being treated. If the matrix material is responsive to induction heating the product itself is heated, and the mold may be made of refractory material, or of stainless steel. The ram is also made of refractory material or of stainless steel.

When mechanical pressure is not used in the vacuum chamber the wheel is preliminarly compressed cold, and simply rests onpedestal 30 within the induction coil. The wheel is directly heated by the induction coil.

It is believed that my improved method of bonding diamond and metal, as well as the advantages of the same, will be apparent from the foregoing detailed description. It will also be understood that while I have described the invention in a preferred form, changes may be made without departing from the scope of the invention, as sought to be defined in the following claims.

I claim:

1. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide and compressing the same to form an embryo abrasive product having some green strength, subjecting the product to direct mechanical pressure and to heat and to environmental vacuum in the presence of a titanium getter until the temperature has risen to a range of 1800 to 2400 F. and the treatment has continued for about six to ten minutes, and thereupon terminating the heating and abruptly cooling by refrigeration while maintaining the direct mechanical pressure and the environmental vacuum until the product is cooled to approximately room temperature.

2. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide and compressing the same, subjectng the product to heat and to environmental vacuum until the temperature reaches about 800 F., treating the product at that temperature for several minutes, continuing evacuation down to a vacuum of about 10- to 10- microns of mercury and at the same time resuming heating to raise the temperature to a range of from 1800" to 2400 F., treating the product at the said elevated temperature for several minutes, and terminating the heating and very abruptly cooling the product by refrigeration down to approximately room temperature.

3. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide, and including also a metal hydride, and compressing the same, subjecting the product to heat and to environmental vacuum until the temperature reaches about 800 F., terminating active evacuation and treating the product at that temperature for about three to five minutes, resuming active evacuation down to a vacuum of about 10- to 10 microns of mercury and at the same time resuming heating to raise the temperature to a range of from 1800 to 2400 F., terminating active evacuation and treating the product at the said elevated temperature for a period of about three to five minutes, and thereupon resuming evacuation and very abruptly cooling the product by refrigeration down to approximately room temperature.

4. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide and compressing the same, subjecting the product to heat and to environmental vacuum until the temperature reaches a range of 400 to 500 F., terminating active evacuation and continuing heating to a temperature of about 800 F., treating the product at that temperature for several minutes, resuming active evacuation down to a vacuum of about l to microns of mercury and at the same time resuming heating to raise the temperature to a range of from 1800 to 2400" F., depending on whether the metal is soft or hard respectively, treating the product at the said elevated temperature for several minutes, and very abruptly cooling the product *by refrigeration down to approximately room temperature.

5. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide tin, nickel, cobalt, chromium boride, and tungsten carbide, and including also a metal hydride, and compressing the same, subjecting the product to heat and to environmental vacuum until the temperature reaches a range of 400 to 500 F., terminating active evacuation and continuing heating to a temperature of about 800 F., treating the product at that temperature for about three to five minutes, resuming active evacuation down to a vacuum of about 10- to 10- microns of mercury and at the same time resuming heating to raise the temperature to a range of from 1800 to 2400 F., depending on whether the metal is soft or hard respectively, terminating active evacuation and treating the product at the said elevated temperature for a period of about three to five minutes, thereupon resuming evacuation for hard metals but not for soft metals and at the same time and in either case terminating the heating and very abruptly cooling the product by refrigeration down to a temperature of about 900 F., and continuing the evacuation for hard metals or resuming evacuation for soft metals while continuing the abrupt cooling down to approximately room temperature.

6. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide and compressing the same to form an embryo abrasive,

product having some green strength, subjecting the prodnot to direct mechanical pressure and to heat and to ening to raise the temperature to a range of from 1800 to 2400 F., treating the product at the said elevated temperature for several minutes, and terminating the heating.

and very abruptly cooling the product by refrigeration down to approximately room temperature.

7. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide, and including also a metal hydride, and compressing the same to form an embryo abrasive product having some green strength, subjecting the product to direct mechanical pressure and to heat and to environ-mental vacuum in the presence of a titanium getter until the temperature reaches about 800 F., treating the pnoduct at that temperature for about three to five minutes, continuing down to a vacuum of about 10- to 10- microns of mercury and at the same time resuming heating to raise the temperature to a range of from 1800 to 2400 F., terminating active evacuation and treating the product at the said elevated temperature for a period of about three to five minutes, and thereupon resuming evacuation and very abruptly cooling the product by refrigeration down to approximately room temperature.

8. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide and compressing the same to form an embryo abrasive product having some green strength, subjecting the product to direct mechanical pressure and to heat and to environmental vacuum in the presence of a titanium getter until the temperature reaches a range of 400 to 500 F., terminating active evacuation and continuing heating to a temperature of about 800 F., treating the product at that temperature for several minutes, resuming active evacuation down to a vacuum of about 10- to 10 microns of mercury and at the same time resuming heating to raise the temperature to a range of from l800 to '2400 F., depending on whether the metal is soft or hard respectively, treating the Product at the said elevated temperature for several minutes, and very abruptly cooling the product by refrigeration down to approximately room temperature.

9. The method of bonding diamond pieces and metal which includes embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten carbide, and including also a metal hydride, and compressing the same to form an embryo abrasive product having some green strength, subjecting the product to direct mechanical pressure and to heat and to environmental vacuum in the presence of a titanium getter until the temperature reaches a range of 400 to 500 F., terminating active evacuation and continuing heating to a temperature of about 800 F., treating the product at that temperature for about three to five minutes, resuming active evacuation down to a vacuum of about 10 to 10* microns of mercury and at the same time resuming heating to raise the temperature to a range of from 1800 to 2400 F., depending on whether the metal is soft or hard respectively, terminating active evacuation and treating the product at the said elevated temperature for a period of about three to five minutes, thereupon resuming evacuation for hard metals but not for soft metals and at the same time and in either case terminating the heating and very abruptly cooling the product by refrigeration down to a temperature of about 900 F., and continuing the evacuation for hard metals or resuming evacuation for soft metals while continuing the abrupt cooling down to approximately room temperature.

10. The method of bonding diamond pieces and metal which includes preliminarily embedding the diamond pieces in a metal powder selected from the group consisting of iron, copper, tin, nickel, cobalt, chromium boride, and tungsten canbide, and including also a metal hydride,

7 and compressing the same to form an embryo article hav- References Cited ing some green strength," subjecting the product to heat UNITED STATES PATENTS and vacuum until the temperature reaches a range or 400 to 500 F., shutting off the evacuation without ad- 2,240,329 5/1941 Bevlufll'd 51309 mitting air and heating to a temperature of about 800 5 2,396,015 3/1946 Lidefl et 51309 F., treating the product at that temperature for several 2, l /1955 Hall 51309 minutes, resuming heating and evacuation to raise the tem 2,737,454 3/ 1956 Danec 51309 perature to a range of from 1800 to 2400 F, and ter- 3,178,273 4/1965 Libal 51309 minating the heating and very abruptly cooling by refrigeration down to approximately room temperature. DONALD ARNOLD, P rimaly Examine"-

Claims (1)

1. THE METHOD OF BONDING DIAMOND PIECES AND METAL WHICH INCLUDES EMBEDDING THE DIAMOND PIECES IN A METAL POWDER SELECTED FROM THE GROUP CONSISTING OF IRON, COPPER, TIN, NICKEL, COBALT, CHROMIUM BORIDE, AND TUNGSTEN CARBIDE AND COMPRESSING THE SAME TO FORM AN EMBRYO ABRASIVE PRODUCT HAVING SOME "GREEN STRENGTH," SUBJECTING THE PRODUCT TO DIRECT MECHANICAL PRESSURE AND TO HEAT AND TO ENVIRONMENTAL VACUUM IN THE PRESENCE OF A TITANIUM GETTER UNTIL THE TEMPERATURE HAS RISEN TO A RANGE OF 1800* TO 2400*F. AND THE TREATMENT HAS CONTINUED FOR ABOUT SIX TO TEN MINUTES, AND THEREUPON TERMINATING THE HEATING AND ABRUPTLY COOLING BY REFRIGERATIN WHILE MAINTAINING THE DIRECT MECHANICAL PRESSURE AND THE ENVIRONMENTAL VACUUM UNTIL THE PRODUCT IS COOLED TO APPROXIMATELY ROOM TEMPERATURE.

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