Effect of Feedstock and Residual Stresses on the Tensile Performance of WC-10Co4Cr Coatings Processed by HVOF

Besides providing surface wear and corrosion resistance, WC-CoCr coatings processed by the high velocity oxy-fuel also have the potential to promote structural reinforcement. In this study, the tensile performance of WC-10Co4Cr coatings, processed by HVOF on double side of 1008 steel substrates, is investigated for feedstocks with different particle size, density, and carbide size, and for two types of fuel, hydrogen and kerosene. Particle diagnostics and in-situ measurement of stresses were performed. Microstructure was characterized by optical and scanning electron microscopy, x-ray diffraction analysis and porosity analysis. Tensile resistance increments, proportional to the degree of compressive residual stresses, were observed for all coatings in comparison to the bare steel. Coatings processed with liquid fuel and bigger particles developed higher kinetic energies, peening and consequently more compressive residual stresses, contributing to a higher increment in tensile strength. On the other hand, in coatings processed with gas fuel, and with feedstock with higher degree of porosity, lower carbide size or lower diameters, the increment in tensile resistance was hindered by the higher degrees of decarburization, associated to longer dwell times and larger surface areas. Results indicate that the tensile resistance increment is strongly associated to the degree of compressive residual stresses.