BG66595B1 - A method for receiving multicomponent multylayer coatings - Google Patents

Abstract

The invention is related to a method for applying multicomponent coatings upon diamond and the ultrahard boron nitride modifications by mixing the abrasive, depending on its application, with a nickel-based alloy (chromium 5-5 %, boron 2-3 %, silicon 3-4 %, and the remaining – nickel), or with titanium powders (8-16 %, tin 10-20 %, the remaining – copper), and at that, depending on the size of the diamond and boron grains, the mixing is 1:1 for the big fractions, and 2:1 volumetric parts of abrasive to the nickel, or copper-titanium alloy. The mixtures are frit, without being pressed, at temperatures 780 to 900 °C, in vacuum 1.3 or 0.013 Pa, depending on the composition of the multicomponent coating. In cases of different use of the ultrahard diamond and boron nitride grains in abrasive tools, by chemical reduction of solutions of copper, nickel, or cobalt ions, upon the multicomponent coatings is additionally applied a coating with thickness 0.008 to 0.010 mm, what alleviates the incorporation of the coated particles in a metal matrix, plastics, or caoutchouc.

Description

The invention relates to a method for producing multi-component, multilayer coatings on diamond or over-rigid modifications of boron nitride (cubic and hexagonal). Multilayer, multicomponent coatings improve the adhesive or chemical interaction of diamond and boron nitride abrasive grains when incorporated into a metal or plastic matrix when tool abrasives are made from them. The instruments produced have increased performance.

The invention relates to methods of powder metallurgy, as well as to the processes of chemical deposition of coatings by reduction in aqueous medium of solutions containing ions of various metals, most commonly nickel, copper, cobalt.

BACKGROUND OF THE INVENTION

Methods are known for the combined chemical and electrochemical deposition of copper, nickel or cobalt, as well as combinations thereof on diamond with particle sizes of 0.1 to 0.6 mm. In order to ensure good mechanical or chemical interaction of the coated diamond particles with the matrix in which they are embedded, the coating must be at least 55% by weight relative to the weight of the diamond or one carat of 0.2 g must be processed to 0 , 3 g. Only in this case, metallized diamond beads are difficult to scrape off from the metal or plastic matrix of the abrasive tool, resulting in increased performance [1].

Methods for titanium or nickel plating of diamond beads are known, using a salt bath of sodium and potassium chloride and calcium carbonate for the purpose of metallizing at 850-900 ° C. The coatings are up to 1 mm thick [2].

Methods for metallizing a diamond by vacuum evaporation of metals are known, most commonly the coatings being nickel, cobalt, titanium, silicon. Excessive modifications of boron nitride are coated with titanium, which helps to moisten grains of other metals [3].

A method has been developed to cover cubic boron nitride with titanium by evaporation in high vacuum using an electron beam of a titanium target. The method is also applicable to cover both boron nitride and diamond grains. Other metals can also be deposited in this way.

There are chemical methods for metallizing diamond grains and excessively rigid modifications of boron nitride. The process is carried out using volatile halogen compounds of titanium, silicon, aluminum, tungsten and other compounds which are introduced into a pre-vacuum chamber in which the metallized grains are heated by means of a gas carrier which is simultaneously a reducing agent such as hydrogen. to 920 + 940 ° C. This method produces thick coatings in comparison with the physical methods of evaporation in vacuum [4].

[5] describes a method for depositing a metallic coating on diamond particles or cubic boron nitride. Metals that are capable of forming a chemical bond with diamond particles and cubic boron nitride are mixed in a powder state and heated to a temperature close to the melting point of the metals. Heating is carried out in an atmosphere that is not oxidizing and does not cause to form bonds between the diamond particles and cubic boron nitride and the coating.

The disadvantages of the listed methods are the following:

- the need to combine chemical and electrochemical deposition of nickel, cobalt or copper to obtain coatings of considerable thickness, providing up to 55% increase in the mass of roofing grains from excess solid materials;

- the use of salt baths is a laborious, unprofitable energy and economic process, the result of the duration of heating and then the removal of salts accumulated on the treated grains;

- Evaporation of metals, such as titanium, nickel, cobalt, copper, silicon and other metals, in vacuum involves the use of expensive equipment in which a device has to be incorporated.

66595 Bl interfering grains of coated superhard materials diamond and boron nitride. The same applies to electron beam evaporation of a metal target. The processes are low-yielding, typically producing thin layers of grain-coated metal;

- The chemical methods for depositing gas phase metal coatings on diamond grains and ultra-rigid modifications of boron carbide are more productive, and thick coatings are obtained. Complex apparatus, a vacuum chemically resistant chamber and pumps are required to carry out the process, since hydrogen chloride is released in the process;

- the above methods do not produce multicomponent coatings, the use of which can be combined with the matrix in which the abrasive beads are incorporated.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for producing multicomponent coatings on superhard materials such as diamond or modifications of boron nitride while avoiding the disadvantages of the above methods under conditions whereby the process of depositing multicomponent coatings is carried out under conditions close to those which produce the bulk of the abrasive products, which makes the process technologically flexible, easily carried out on a case-by-case basis.

The object of the invention is solved by mixing diamond grains or ultra-rigid modifications of boron nitride with fine powders, the particle sizes of which are at least four to ten times finer in grain. In the granularity of superhard diamond particles and those of boron nitride 0.1 to 0.6 mm, the powders with which they are mixed must have a grain size of 0.06 mm.

Powders contain carbide-forming elements (chromium, titanium, etc.) when handling diamond grains. When handling ultra-rigid modifications of boron nitride, the powder contains titanium. The powders used for applying multicomponent compositions to diamond contain, in addition to the carbide-forming element, also nickel, boron, silicon and iron. In cases where titanium is used, the powders contain copper and tin.

Well homogenized mixtures of diamond or boron nitride particles are sintered without pre-pressing in a vacuum of 1.3 to 0.013 Pa or in an atmosphere of hydrogen, argon or a mixture of hydrogen and nitrogen. The sintering, depending on the powder composition, is carried out at 780 ^ 820 ° C using a copper composition or at 880 ^ -900 ° C when the powder contains nickel. As a result of diamond or boron nitride particle sintering, a layer of alloy from the starting powder composition used is formed on these multicomponent layers, further depending on the purpose of the fabricated tools, thin-layer up to 0.008 mm coatings obtained by chemical deposition. nickel, cobalt, copper or combined of the three metal layers.

The invention, the essence of which is described above, has the following advantages:

- The use of abrasive materials such as diamond and the ultra-rigid modifications of boron nitride grains which are coated with multicomponent layers increase the performance (wear resistance, hardness, reduced abrasive content) of the instruments in which they are embedded;

- The need to use sophisticated coating equipment on superhard materials incorporated in the working part of abrasive tools has been eliminated;

- The powders used for the application of the multilayer coatings are the same as the treated abrasives. The same facilities in which the tools are made are used;

- The additional thin film, chemically deposited coating on the abrasive grains facilitates the processing of the tool at the initial stage of the abrasive process of removing material from the workpiece.

Examples illustrating the invention

The invention finds application in the practice of manufacturing abrasive tools.

When tools are made by hot pressing at 2.5.10 ³ to 3.5.10 ³ Pa and 750-850 ° C.

Depending on the production method of the abrasive tool and the matrix in which

66595 Bl will be incorporated coated with a multicomponent layer of abrasive grains to select and composition of the coating.

To the first group of production methods:

Example 1. For the manufacture of abrasive diamond tools, diamond beads with a size of 0.6 to 0.1 mm are mixed with powder with a particle size of less than 0.06 mm from a nickel-chromium alloy (for example chromium 12%; boron 2- 3%, silicon 3-4%, the rest is nickel). The mixing is in a ratio of 1: 1 parts by volume of the powder of the alloy to the particles of the superhard material. The mixture was homogenized well and baked at 880 + 900 ° C in a vacuum of 1.3 Pa for 15 min. After cooling, the sintered mixture is crushed, sieved through a sieve according to the size of the alloy coated solids and subjected to chemical coupling to give a copper layer of 0.005 to 0.008 mm thick. The decayed grains are embedded in copper-based segments produced by hot pressing at 750 + 800 ° C and 3.1O ³ Pa pressure.

Example 2. In the case where articles (segments, abrasive discs, etc.) of compositions predominantly containing cobalt, nickel or iron are manufactured, a multicomponent coating is applied to the diamond abrasive grains by grinding the diamond with a powder containing 8 ^ -12% titanium, 12 + 20% tin, the rest is copper. As in Example 1, the particle size of the titanium powder, copper and tin should be less than 0.063 mm. The sintering was carried out in a vacuum of 0.013 Pa or in a protective argon medium for 15 min at 780 + 820 ° C. The crushed specks are sifted. Diamond grains coated with a titanium-copper-tin alloy are cobalted or nickel-plated chemically, with an additional coating layer of not more than 0.010 mm. The multilayer coated diamond is mixed with the main metal matrix from which the corresponding article is made and sintered by hot pressing at 850 ° C in a graphite matrix at a pressure of 3.1 Ο ³ Pa.

EXAMPLE 3 Ultra-rigid modifications of boron nitride are difficult to wet with metallic compositions based on copper or on metals of the iron group. To incorporate cubic boron nitride grains into the matrix of these metal compositions, the particles must be treated with a titanium-copper tin-based alloy with a titanium content of not less than 8%. As in Examples 1 and 2, boron nitride particles were mixed with a powder of size less than 0.063 mm with a composition of 8-4% titanium, tin 10 + 20%, the rest copper. The well-homogeneous mixture of boron nitride and the powders of the metal composition is sanded in a vacuum of 0.013 Pa at 780 + 800 ° C. The sintered powder mixture is crushed and sieved through a sieve corresponding to the size of the multilayered coated boron nitride particles.

In cases where the boron nitride particles are incorporated into a metal matrix containing copper, no further coating on them of a thin film coating obtained by chemical metallization is used.

When the metal matrix from which segments or other articles are made is based or predominantly containing metals of the group of iron, a further coating of cobalt or nickel with a thickness of 0.008 + 0.010 mm is applied by chemical reduction in solution.

Hot pressing of products containing abrasive boron nitride coated with a multilayer coating containing titanium is carried out in specialized hot presses, which operate in a vacuum up to 0.013 Pa at a temperature up to 900 ° C and a pressure of 3.10 ³ Pa.

Claims (3)

Claims 1. A method for producing multi-component, multi-layer coatings on diamond grains and, grains of ultra-rigid modifications of boron nitride, which is accomplished by mixing abrasive grains with nickel-based alloy powders (chromium 5 + 15%, boron 2 + 3 %, silicon 3 + 4%, the remaining nickel), or with titanium powders 8 + 15%, tin 10 + 20%, the remaining copper, characterized in that the well-homogenized mixtures, without being compressed, are crushed at 880+ 900 ° C when the powder is nickel-based or at 780 + 820 ° C when copper-based, the firing being carried out in in vacuo 1.3 to 0.013 Pa or in a protective hydrogen, argon or hydrazoic atmosphere, the filter composite is crushed and screened and individual grains of abrasive-coated multi-component coating additionally by chemical means is coppering, nickel or cobalting. 66595 Bl Method according to claim 1, characterized in that the diamond beads of dimensions 0.6 to 0.1 mm are mixed with a nickel base powder, with the nickel alloy particles having a size less than 0.063 mm and a ratio of $ abrasive and the alloy powder is 1: 1 by volume, the resulting multi-component dust particles being further chemically reduced. A method according to claim 1, characterized in that the diamond abrasive grains or the superhard boron nitride modifications are coated with a multicomponent titanium-copper alloy coating, the coating being applied by mixing 15 powders. such as size abrasive particles 0.6 to 0.1 mm are mixed with copper-titanium tin powders with a particle size less than 0.063 mm at an abrasive-to-metal powder ratio of 1: 1, with a nickel or cobalt chemical coating applied to the particles. way.