Effect of Surface Processing of CoNiCrAlY Coatings on Oxidation Behavior of This Coatin

In this study, the effect of surface processing of CoNiCrAlY coatings on oxidation behavior of this coating has investigated. The HVOF method used for deposition of CoNiCrAlY coating on the Inconel 617 substrate. The surface of coatings polished with grand paper No. 40, For investigation effect of surface processing and removing of oxide layer that formed during thermal spray on oxidation behavior of CoNiCrAlY coating. Then the samples oxidized in 1050 °C for 100 hrs. The Scanning Electron Microscope (SEM), X-ray Diffraction and surface profilometer used for microstructure and topographical investigation. Results show that surface polishing of coatings caused to developing of oxidation behavior of CoNiCrAlY coatings. The formed oxide layer on the surface of this coating after 100 hrs oxidation is α-Al2O3 that prevented of more oxidation of coating. The oxidation rate of coating with surface polishing calculated about 0.1×10-13 (10-10 gr2 cm-4 h-1)that is 16 times lower than coating without surface polishing. The oxide layer morphology formed on polished coating has globelar-like morphology that researchers believed that this morphology related to α-Al2O3 phase but in the non-polished coating, the surface morphology of oxide scale formed of polyhedral particles. This morphology related to spinel, CoO and NiO oxides.