WC-Co coatings and sinters modified with nano-sized tic microstructure – quantitative evaluation

The different concepts of WC-Co thermally sprayed coatings improvement may be considered and the application of nanoparticles, as the mechanical strengthening addition, is one of them. Nanostructured WC-Co coatings are characterized by higher hardness than the coatings formed from micrometric WC grains; whereas coatings with bimodal distribution of particles reveal greater wear resistance than the coatings obtained exclusively from nano-sized powders. Mixed effect of the matrix reinforcement by nanoparticles and strong fix of the micron-sized WC grains was proposed as a possible reason for enhanced wear resistance of bimodal coatings. In order to obtain a bimodal distribution of particles in the material standard WC-Co (83-17) powder was mixed with nanometric TiC powder (40–100 nm). The amount of TiC in powder mixtures was in the range from 1 to 7 wt.%. The mixtures were deposited on steel substrate using HVAF method and also hot pressed in vacuum. The microstructure of obtained coatings and sinters was quantitatively evaluated. Sinters revealed more homogenous distribution of the nano-sized TiC particles than the coatings. The addition of nano-sized TiC in the case of coatings has led to the decrease of its porosity. The agglomeration of nano-sized TiC particles in the coatings results in the decrease of material’s hardness.