Impact wear of an HVOF-sprayed Cr3C2-NiCr coating

In this study, a Cr3C2-NiCr coating was produced by high velocity oxy-fuel (HVOF) spraying and investigated in terms of its behavior under cyclic impact loading using impact test, which is usually established to evaluate PVD and CVD hard coatings. The Cr3C2-NiCr coating was exposed to forces of F = 300 N, F = 500 N, F = 800 N and F = 1000 N with number of cycles varying from n = 1.25 ∗ 105 to n = 10 ∗ 105. The tested samples were analyzed with confocal laser scanning microscopy, optical light microscopy and electron scanning microscopy on the impacted surfaces as well as on the cross-sections of the selected samples. It is identified that under the forces of F = 300 N, F = 500 N and F = 800 N the coatings are subjected to cohesive failure, which can be attributed to different mechanisms. Under F = 1000 N loading, failure occurs at the interface between coating and substrate as well. The local plastic deformation, tribo-reaction and micro-abrasion cause only marginal change in crater volume generated due to cyclic loading, while rupture of the coating parts result in significantly higher material losses. The significance of the partial coating rupture depends strongly on the applied force. With a loading force of F = 800 N and higher, partial coating rupture and delamination of coating segments are observed. This study shows that the impact testing can be successfully applied on thermally sprayed coatings to evaluate their impact wear.