Deposition and characterization of WC-Co hard-metal coatings by high velocity oxy-fuel process combined with dry-ice blasting

The residual stresses arising during high velocity oxy-fuel (HVOF) process usually restrict the building up of thick coatings. The potential of in-situ dry-ice blasting treatment during HVOF process to deposit thick WC-Co coatings with high quality due to its efficient cooling and mechanical peening was investigated in the present work. Characterization of WC-Co coatings deposited by HVOF combined with dry-ice blasting was carried out and compared with that of the coatings prepared using conventional HVOF. Several techniques, including scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy, were used to characterize the microstructures and phase distribution of the powders and coatings. In addition, mechanical properties such as hardness and sliding wear resistance were evaluated. The results demonstrate that HVOF-sprayed WC-Co coating with dry-ice blasting is characterized by compact construction, grain refinement as well as high hardness. Different from the prevention phenomenon of decarburization observed for plasma spraying of austenitic steel, WC decarburization still occurs for HVOF-sprayed WC-Co coating with dry-ice blasting. The in-situ dry-ice blasting treatment results in minute improvement in wear resistance of WC-Co coatings.