Microstructure and Hardness of Tungsten Coating for High Heat Resistant Material Produced by Means of Gas Tunnel Type Plasma Spraying

摘要

Tungston (W) is the metal which has the highest melting point of 3422 ℃, therefore when deposited as a coating it can protect the substrate surface from high heat flux. The W composite produced by coating methods will be a superior candidate for aerospace materials which require high heat resistance (such as TBC). Thermal spraying method is one of potential candidates to produce W composites. In this study, pure W coatings were produced on stainless steel substrates by gas tunnel type plasma spraying at a short spraying distance (40-50mm). Regarding the microstructure, the W coating contained some pores. The Vickers micro-hardness of the W coating was measured as the mechanical property. The W coating had a hardness of Hv=260-320 along its cross section, which is a little lower than the hardness for bulk tungsten. The results of X ray Diffraction showed that the coating consists of pure tungsten, without oxidation.