Effect of the Microstructure of Cermet Powders on the Performance Characteristics of Thermal Spray Coatings

Resumo

Comparative analysis of the performance characteristics of thermal spray coatings, in particular, detonation coatings formed from commercial tungsten-carbide-based WC−Со (12 wt %) powder (1342VM, Praxair, United States) and cermet TiC−Ме (19 vol %) powder (Ме = NiCr, Co) obtained by self-propagating high-temperature synthesis followed by spheroidization in a plasma jet is performed. It is shown that carbide particles of the cermet powder with a size of greater than 3 µm have structural defects in the form of cracks and pores. Their appearance is explained phenomenologically. It is established that spheroidized particles inherit the internal microstructure. They are dense, whereas the porosity of tungsten carbide based WC−Со (12 wt %) particles attains 40%. The effect of the density of particles on the powder-deposition efficiency and the porosity of coatings is revealed. When a dense powder is sprayed, its deposition efficiency is decreased from 54 to 33%, and the porosity of coatings increases from 0.4 to 1.78%. The WC−Со (19 vol %) coating has the best wear resistance due to the splinter shape of carbide particles with a size of nearly 1 µm.