Electrical discharge coating method and green compact electrode used therein

Abstract

An electric discharge coating method comprises the steps of generating a pulse discharge between a green compact electrode (3) and a processing object surface (20) in working fluid (10), transferring a component of the green compact electrode (3) onto the processing object surface (20), and forming a coating (21). Using the green compact electrode (3) which is compression-molded with metallic powder as a major component and includes, on the surface thereof, an oxide layer thicker than an oxide coating normally obtained in air at normal temperature, a metallic component of the green compact electrode (3) is transferred onto the processing object surface (20) to form the coating (21) containing the metallic component as a major component. A thick coating mainly composed of high-hardness metal can be formed even for low-melting metal such as an aluminum material without depending on a carbide for lowering electric conductivity.

Description

technical field [0001] The present invention relates to a discharge coating method in which an object to be processed is pulse-discharged using a compact electrode such as metal powder to coat the surface of the object to be processed, and particularly relates to a discharge method capable of forming a hard thick-film coating on a low-melting-point metal such as aluminum. The powder electrode used in the coating method and the discharge coating method. Background technique [0002] Aluminum and aluminum alloys (hereinafter referred to as aluminum materials) are light in weight and excellent in workability, but they also have disadvantages of poor wear resistance and corrosion resistance. Therefore, conventionally, vapor deposition treatments such as anodizing, PVD, and CVD have been developed as surface treatment methods for coating the surface of an aluminum material with a harder coating. In addition, in order to shield aluminum materials with poor high-temperature streng...

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Problems solved by technology

[0007] However, in the discharge coating treatment of the green powder electrode mixed with the above-mentioned difficult-to-carbonize metal, for a low melting point metal such as aluminum, the segregation of the aluminum material is affected by the heat generated by the discharge compared with the segregation of the electrode material. More, it is difficult to migrate the electrode material and its carbides to the aluminum surface

[0008] If the applied voltage is lowered and the pulse width is increased to suppress the melting of aluminum, the reaction time with the dissociated carbon atoms from the machining fluid will be prolonged, so even for metals that are relatively difficult to carbonize, the ratio of carbonization will vary. Larger, based on the reasons mentioned above, can not achieve thick film

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