FR2969178A1 - Diamond coating of tungsten carbide tools by chemical vapor deposition without chemical preparation of carbide, comprises depositing intermediate layer of silicon carbide on tools, and microbead blasting tools with silicon carbide - Google Patents

Abstract

The process comprises depositing an intermediate layer of silicon carbide (SiC) on the tools using low temperature plasma at atmospheric pressure, microbead blasting the tools with SiC for etching and implanting SiC microparticles (5) between carbide grains (7), coating the tools with a layer (4) of CVD SiC produced by plasma of nitrogen and methane at low temperature and atmospheric pressure. The tools are made of tungsten carbide with cobalt binder. The layer of SiC is subjected, in an ultrasonic bath, a germination operation that implements diamond grains (6) on a surface of the SiC layer. The process comprises depositing an intermediate layer of silicon carbide (SiC) on the tools using low temperature plasma at atmospheric pressure, microbead blasting the tools with SiC for etching and implanting SiC microparticles (5) between carbide grains (7), coating the tools with a layer (4) of CVD SiC produced by plasma of nitrogen and methane at low temperature and atmospheric pressure. The tools are made of tungsten carbide with cobalt binder. The layer of SiC is subjected, in an ultrasonic bath, a germination operation that implements diamond grains (6) on a surface of the SiC layer. A CVD diamond layer (1) is deposited on the layer of SiC.

Description

The present invention relates to a method for producing CVD diamond layers (1) on an SiC intermediate layer (4) deposited on the carbide tools (2) by low temperature plasma and at atmospheric pressure. The traditional CVD diamond coating of tungsten carbide tools is generally performed after a chemical treatment which decreases the% of the cobalt binder at the surface on the part to be coated. This chemical operation weakens the mechanical properties of the carbide and rounds the cutting edges of the tools. (3) The method according to the invention overcomes these disadvantages by eliminating the chemical treatment, retaining after CVD diamond coating the mechanical properties of the carbide and the sharpness of the cutting edges (3) of the tools. According to particular embodiments, the tools are made of WcCo tungsten carbide with a percentage of cobalt which can vary from 3 to 12% The particle size of the tungsten grains is between 0.5 to 5 microns. Carbides should not have mixed carbide in their composition. The surface to be coated is microbilled with SiC grains 800, air pressure of the microbrilling 2 bars distance nozzle / piece 100 mm perpendicular to the surfaces to be coated for implantation of SiC grains (5) between the carbide grains (7) of the tool. The tools are then coated with a CVD (4) SiC layer by a plasma process at low temperature and at atmospheric pressure. Plasma with N2 + CH4 (14) Proportions N2 501 / min CH4 0.51 / min. Nozzle (10) at 40 mm from the tool, sweeping speed 30 m / min, 15 passes on the tool. At the base of the nozzle (10) in the plasma (11) introduction of a precursor (12) of the C6H18Si2 type. The flow rate of the precursor (12) of the order of 25 ml / min and the flow rate of the carrier gas (13) of 201 / min. for the creation of the SiC layer (4) on tungsten carbide. The plasma jet (11) is perpendicular to the surface to be treated (8). These parameters make it possible to produce SiC layers (4) with a thickness (9) of 0.5 to 1 micron. This thickness is sufficient to create an effective barrier against cobalt rising through the SiC layer. Before the CVD diamond coating, the tools are immersed in an ultrasonic bath with diamond grains in suspension to create germination zones by implantation of diamond grains (6) in the SiC layer (4). This operation engraves the surface of the layer of SiC (4) and promotes the grip of the diamond coating.

The 40HZ ultrasonic bath contains a mixture of 1L DI water with 2 carats of 0.5 micron diamond powder. The treatment time is about 10 minutes. The tools are then coated in a diamond CVD oven at about 800 ° C. After treatment, the coating thickness is typically 6 microns. The process according to the invention is intended to coat the tungsten carbide tools with a CVD diamond coating by removing their chemical preparation.

Claims (6)

CLAIMS1) Method for CVD diamond coating tungsten carbide tools without chemical preparation of carbide, characterized in that prior to the realization of the diamond coating by CVD, is deposited on the tools an intermediate layer of SiC by low temperature plasma and at atmospheric pressure. 2) Process according to claim 1, characterized in that the tools are made of 1 tungsten carbide with cobalt binder. 3) Process according to the preceding claims, characterized in that prior to the deposition of the SiC intermediate layer, the WC tools are microbilled with SiC to strip and implant SiC microparticles (5) between the carbide grains ( 7). 15 4) Process according to the preceding claims, characterized in that following microbilling, the tools are coated with a layer of SiC CVD (4) made by plasma (11) of nitrogen and methane, at low temperature and at atmospheric pressure. . 5) Method according to the preceding claims, characterized in that the SiC layer undergoes in an ultrasonic bath a germination operation which implements diamond grains (6) on the surface of the SiC layer (4). 6) Method according to the preceding claims, characterized in that the diamond CVD layer (1) is deposited on the SiC layer (4).