DE2124637A1 - Abrasive particles - Google Patents

Description

OR-INQ. DIPL.-ΙΝβ. M. TC. riPU.-FHYS. OT OIPU.-PHVS.

HÖGER -STELLRECHT-GRIESSBACH - HAECKER

PATENT LAWYERS IN STUTTGART

38 862 ra 2124637

May 18, 1971
a - 133

De Beers Industrial Diamond Division Limited
45, Main Street

Johannesburg, Transvaal
South African Republic

Abrasive particles

The invention relates to an abrasive particle on which a Coating is applied. It is known to have abrasive particles to be provided with a metallic coating. Such coated Abrasive particles find an application in the work surfaces of grinding tools, with the coating of the particle makes it less sensitive, insofar as it emerges from the matrix or from the storage point in the grinding surface can be lifted out or torn away during the grinding process.

The present invention is based on the object of providing a coating for an abrasive particle which thickened compared to known coatings of this type

109849/1260

38 862 m

May 18, 1971

a - 133 j

Has properties.

To solve this problem, the invention is based on and consists of an abrasive particle of the type described above in that a composite coating is provided with a first layer of a suitable metal and a second layer of a suitable different from the first Metal, and that the metal of each layer constitutes between 20 to 80 percent by weight of the abrasive particle. Preferably the composite coating amounts to 50 to 150 percent by weight of the abrasive particle. Suitable metals are, for example, nickel, copper, iron, cobalt, chromium and alloys made from these metals.

According to one embodiment of the invention, a composite coating for an abrasive particle consists of a first nickel layer and a second copper layer, the nickel layer preferably being 43 percent by weight of the diamond used as the abrasive particle and the copper layer preferably makes up about 57 percent by weight of the diamond.

In another embodiment of the present invention, the composite coating is for an abrasive particle of a first layer of an alloy, preferably a nickel-iron alloy, and a second layer Copper, with the alloy preferably between 50 to 80 percent by weight of the particle and the copper preferably makes up between 20 to 50 percent by weight of the particle. If the alloy is a nickel-iron alloy, then the alloy preferably contains between 36 to 43% nickel.

3 -

10984S / 1260

38 862 m
May 18, 1971
a - 133

212Λ637

In both embodiments, the outer layer is preferably a copper coating.

Furthermore, a (thin) coating of bronze with a high copper content can be applied over the outer surface of the outermost layer If a bronze coating is provided, this preferably comprises two percent by weight of the coated one Particle on.

The abrasive particles can be diamonds, cubic " Boron nitride, silicon carbide, tungsten carbide or similar materials Act.

The two metal layers can be applied to the particle by means of methods known per se, either electrolytically or without using the electric current. An example of a suitable method for electroless nickel plating can be found in British Patent 1,198,479. Examples of electrolytic plating can be found in the Union Patent 66/5310, the publication "Electroplating Engineering Handbook" by A. K-. Graham 1955, Rheinhold and the publication "Electrodeposition of Alloys Principles and Practice," Volume II Abner Eren- i ner, Academic Press New York and London, 1963, page 265 to known.

In the case of a nickel layer, the nickel is preferably electrolytically plated onto the particle, namely under Use of nickel sulfamate as a source for the nickel ions in the plating solution. Such a method is described in the German patent application.

Diamonds that are coated with the coatings described above are for both wet and dry Schreifvorgee suitable.

109849/126 0

38 862 m '.

May 18, 1971

a - 133 _k y

"212Λ637

Experiments were carried out using RD diamond grit, with a composite coating such as described earlier, had been applied. Standard dry grinding conditions were used (with an infeed of 0.025 mm; one mil). The results of these tests are given in Table 1 below:

Tabel Coating G ratio

Copper plating according to the usual

Art (100 %) 54.1

one made from 43 % nickel-57 % copper
composite coating 58.4

one made of 50 % Ni-Fe alloy
(43 % nickel content) -50 % copper
composite coating 63.8

The G-ratio is the ratio of the proportion of metal that is removed from the workpiece during the grinding process is to the proportion of the grinding tool used. The larger the G-ratio, the more suitable the coated one Diamond for grinding operations. As can be clearly seen from the test results given above, the diamonds coated according to the invention have i «i ratio to diamonds coated in the usual way on outstanding properties.

In the comparative tests, plastic-bound, Cup-shaped grinding wheels (Schmirgeibassen) used, whereby the concentration of diamonds in the abrasive matrix in each case was 100 carats, i.e. 72 carats per cubic inch.

10S8A9 / 1260 - 5 -

Claims (13)

862 m
May 18, 1971
a - Claims Abrasive particles to which a coating is applied, characterized in that a composite coating is provided with a first layer of a suitable metal and a second layer of a suitable metal different from the first, and that the metal of each layer is between 20 to 80 percent by weight de _s abrasive particle matters. 2. Abrasive particles according to claim 1, characterized in that g e k indicates that the composite layer is between 50 to 150 percent by weight of the particle amounts to. 3. Abrasive particles according to claim 1 or 2, characterized characterized that the metal is made up of the nickel, copper, cobalt, iron, chromium and these alloys Metals comprehensive group is selected. 4. S chTe if particles according to claim 1 or 2, characterized characterized in that the metal of the first layer is nickel and the metal of the second layer is copper is. 5. Abrasive particles according to claim 4, characterized that the copper layer is the outer of the two layers., 6. Abrasive particles according to claim 4 or 5, characterized characterized in that the nickel layer is about 43 percent by weight of the particle and the copper layer is about 57 percent by weight. - 6 10 9 8 4 9/1 260 862 m
May 18, 1971
a - 133 7. Abrasive particles according to claim 1 or 2, characterized marked that the metal of the first layer is a nickel-iron alloy and the metal of the second layer is copper, 8. Abrasive particles according to claim 7, characterized that the copper layer is the outer of the two layers. 9. Abrasive particles according to claim 7 or 8, characterized characterized that the alloy is about 50 up to 80 percent by weight of the particle and the copper makes up about 20 to 50 percent by weight of the particle by weight. 10. Abrasive particles according to one of claims J to 9 »characterized in that the alloy contains between 36 and * 13 % nickel. 11. Abrasive particles according to one or more of the claims 1 to 10, characterized in that that on the outer surface of the outermost layer a bronze coating with a high copper content is applied. 12. Abrasive particles according to one of claims 1 to 11, d a through characterized in that the particles of diamonds, cubic boron nitride, silicon carbide, Consists of tungsten carbide or similar material. 13. Grinding tool, characterized in that that it contains abrasive particles according to one or more of Claims 1 to 12 in the abrasive surface. 109849/1260