CVD Diamond Coated Carbide Cutting Tool Pretreatment—Plasma Etching

Plasma etching is one of processing that can be applied in most of matrix, which including plasma cleaning, plasma activation, plasma coating for some complicate structure. It can not only remove cobalt (Co), but also has decarburization when it used in CVD diamond coated carbide cutting tool, which uses H, O, Ar atom or ion and CO in H₂, O₂-H₂, H₂O-H₂, CO-H₂, Ar-H₂ to react with tungsten carbide (WC) and binder phase cobalt (Co) forms CO₂, CH₄, Co(CO)₄, Co(OH)₄ and other compounds and Co hydrates with highly volatile. So pure tungsten carbide surface to form a layer of a certain thickness, beginning after the deposition of the diamond layer is carbonized again produce a chemical bond and form new tungsten carbide WC particle.

As a result, in the early stage of diamond deposition, CVD diamond coating between the substrate and the formation of carbide cutting tools tungsten carbide （WC）intermediate layer. It not only can effectively reduce the residual stresses present in the film, but also to some extent, but the barrier of Matrix diamond growth had spread to the deep cobalt heavy surface, and the diamond crystals embedded into the WC grain boundaries, so that the diamond the contact area between the film and the cemented carbide substrate is improved, resulting in "pinning" effect, effectively improving the inter-layer film with the adhesion between the film and the substrate. Plasma etching is a form of dry etching, the principle is exposed to the gas to form a plasma electron region, electricity gas and the resulting release of gas energy electrons to form a plasma or ion, electricity gas when atoms accelerated by an electric field, it will release sufficient strength and surface forces expelled only adhesive material or etched surface. In addition, plasma etching can be specifically divided into reactive plasma (RIE), downstream plasma, direct plasma and so on.

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