Effect of Surface Roughness Morphology on Bond Strength of Thermal Sprayed WC-10Co-4Cr Ceramic/Metal Coating

In this study, the effect of surface roughness and roughness morphology on the bond strength of WC-Co-Cr coatings has investigated. The three different surfaces morphology are use for this purpose. The first and tow samples sandblasted with alumina and silicon carbide respectively. Other sample no sandblasted before spraying process. The same WC-10Co-4Cr coating deposited on the substrates with HVOF methods. The morphology of powder, coating and substrate surface roughness has investigated with scanning electron microscopy (SEM) and the surface roughness meter used for measurement of surface roughness. The phase study of powder and coating are doing with X-ray diffractometry. Coatings bond strength has investigated with pull off test. The phase investigated show that decomposition of WC phase is very low during thermal spray process. Porosity in the WC-10Co-4Cr coating that calculated with image analysis is about %1.6, whereas the hardness is 1180 HV. The pull off test results show the non-sandblasted substrate after coating process shows higher bond strength. Probably work hardening during sandblasting prevent of WC particles penetration into copper substrate. This phenomenon to cause the fracture mode in alumina and SiC was adhesion and cohesion respectively, while Fracture in the non-sandblasted coating occurs in epoxy.