Evaluation of mechanical properties of WC-Co and CrC coatings obtained from powder and flexible cored wire feedstock materials

Abstract

This paper assesses the microstructure, porosity, microhardness (Hv ) and fracture toughness (KC) of cemented carbides coatings deposited by High-Velocity Oxygen Fuel (HVOF) and Flame (FSFC) spray processes. Three types of coatings were applied for each process from similar feedstock materials in powder and cored wire form. Measurements of fracture toughness were conducted with the Vickers indentation method in the cross section of the deposited layers. An image processing system was applied for the analysis of porosity, showing a globular morphology of the pores in both processes. The experimental results allowed corroborating that the coatings applied by HVOF using powder feedstock have lower porosity than those achieved with the Flame Spray of cored wire material (FSFC). In HVOF and FSFC processes, the porosity of the coating could be an important factor, but when kept in low values, the decrease in Hv and KC are mainly related to the microstructural changes in the coating. The results also allow considering the FSFC technique as a feasible alternative particularly in applications such as internal part of industrial pipes where it becomes difficult to use HVOF due to accessibility problems.