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

In this study, the effects of surface roughness and roughness morphology on the bond strength of WCCo- Cr coatings have been investigated. Three different surface morphologies are used for this purpose. The first and second samples were sandblasted with Alumina and Silicon Carbide, respectively. The other sample was not sandblasted before spraying process. The same WC-10Co-4Cr coating was deposited on the substrates through HVOF methods. The morphology of powder, coating and substrate surface roughness have been investigated by using Scanning Electron Microscopy (SEM), and the surface roughness meter was used for measuring the surface roughness. The phase study of powder and coating was done by X-ray diffractometry. Coatings bond strength has been investigated by pull-off test. The investigated phase showed that decomposition of WC phase is very low during thermal spray process. C Porosity of the WC-10Co-4Cr coating which was calculated by using image analysis is about %1.6, whereas the hardness is 1180 HV. The pull-off test results showed that after coating process, the non-sandblasted substrate shows higher bond strength. Probably work hardening during sandblasting prevents WC particles penetration into Copper substrate. This phenomenon caused adhesion and cohesion fracture mode in Alumina and SiC, respectively, while fracture in the nonsandblasted coating occurs in epoxy.