Microstructure and properties of in-situ Ti5Si3-TiC composite coatings by reactive plasma spraying

Abstract

Ti powders, Si powders, and sucrose as a carbonaceous precursor were used to prepare Ti-Si-C composite powders by a spray-drying/precursor-pyrolysis technology. Ti-Si-C composite coatings were in-situ synthesized by reactive plasma spraying of Ti-Si-C composite powders. The microstructure and properties of the composite coatings were investigated. The results showed that the composite coatings consisted of in-situ formed Ti5Si3, TiC and Ti3O. The TiC particles with a diameter of hundreds of microns formed into clusters. The Ti5Si3 and Ti3O with sizes of about 20–40 nm coexisted in the lamellae. The microhardness of Ti5Si3-TiC composite coatings is up to 1906 HV0.1, about 4 times higher than that of TC4 alloys because of the nano Ti5Si3 and the submicron TiC grains. The composite coatings showed excellent wear resistance at room temperature and high temperature (600 °C), about 170 times and 40 times that of TC4 alloys, respectively. The oxidation tests suggested that the Ti5Si3-TiC composite coatings improved the oxidation onset temperature and have an oxidation weight change half of that of the TC4 alloys.