Microstructure and high-temperature wear and oxidation resistance of laser clad γ/W 2C/TiC composite coatings on γ-TiAl intermetallic alloy

Abstract

There are very strong interests in improving the high-temperature wear resistance of the γ-TiAl intermetallic alloy, especially when applied as tribological moving components. In this paper, microstructure, high-temperature dry sliding wear at 600 °C and isothermal oxidation at 1000 °C on ambient air of laser clad γ/W 2C/TiC composite coatings with different constitution of Ni–Cr–W–C precursor mixed powders on TiAl alloy substrates have been investigated. The results show that microstructure of the laser fabricated composite coatings possess non-equilibrium microstructure consisting of the matrix of nickel-base solid solution γ-NiCrAl and reinforcements of TiC, W 2C and M 23C 6 carbides. Higher wear resistance than the original TiAl alloy is achieved in the composite coatings under high-temperature wear test conditions. However, the oxidation resistance of the laser clad γ/W 2C/TiC composite coatings is deceased. The corresponding mechanisms resulting in the above behaviors of the laser clad composite coatings are discussed.