Residual stresses in WC-Co coatings in As-sprayed and surface-ground conditions

The mechanical integrity of WC-Co coatings is critical for their performance in wear, corrosion, and impact resistance applications. Residual stress, with its role in development of cracking, micro-cracking, and delamination, is another integral part of the mechanical characterization of the coated systems. In the given study, the residual stress of the WC-Co coatings on steel and stainless steel substrates was examined in two conditions, after deposition and after subsequent surface grinding. Several experimental techniques, including bi-layer curvature, x-ray diffraction, and neutron diffraction, were used to assess residual stress in the coatings and to enable comparison between the methods. Residual stresses induced by deposition are mostly due to rapid particle quenching and solidification upon impact, as well as any cold working induced by high velocity particle impact, but for the WC ceramic particles both effects are insignificant and result in small deposition stress. Thermal mismatch between materials of coating and substrate is the major source of stress and scale accordingly to the CTE of the substrate and coating materials and deposition temperature. It was demonstrated that the grinding applied to surface does not modify the as-sprayed residual stresses in the coatings significantly therefore assuming absence of microcracking that could have potentially affect the residual stresses.