Applicability of MSCoating to titanium aluminide substrate - new coating and cladding technology using electro-discharge energy

摘要

Titanium aluminide of light weight heat-resistant alloy comes into various applications such as an impeller in turbocharger, as an aeration and evacuation valve in gasoline engine, as a rotor blade in jet engine, and so on, instead of nickel-based alloy parts with heavy weight. However, titanium aluminide provides so poor wear resistance, that it is necessary to build-up coating material with wear resistance. But, it is impossible to coat the surface by welding, because of the heat shrink crack due to lower ductility of titanium aluminide. Therefore, a wear-resistant coating on titanium aluminide substrate has been made by plasma spraying after not so easy preparation, though the coating is apt to peel off. Micro Spark Coating (MSCoating) technologies, which can stably build up functional coating and cladding, have been developed for various kinds of substrates. MSCoating is an electrical discharging technique using an electrode containing either metal powder or ceramic powder, and can form high wear resistant film efficiently. MSCoating gives the substrate less heat stress, so as to build up the coating without peeling. In addition, this coating does not take long time for preparation. Stellite films formed on nickel alloy substrates using this technique, for example, have been served for jet engine parts under high temperature combustion gas, which demonstrates the high reliability of this technology. In this report, the applicability of MSCoating to titanium aluminide substrate was investigated and discussed.