Nanoindentation characterization of the surface mechanical properties of a 17-4PH stainless steel substrate treated with grit blasting and coated with a Cr3C2-NiCr coating

Grit blasting with alumina particles offers a conventional substrate surface preparation method intended to improve the adhesion of thermal spray coatings. However, the associated microstructural modifications to the substrate may, in fact, reduce the integrity of the interface. In this paper, we use nanoindentation cartography methods to characterize the local mechanical properties of the interface of a HVOF coating deposited on an alumina grit blasted 17-4PH stainless steel substrate. The results show a hardness gradient in the substrate, which we evaluate within the context of the refinement of the substrate microstructure. We show that nano-hardness mapping, combined with Atomic Force Microscopy and Scanning Electron Microscopy analysis provides a viable approach to study this unique contribution of the microstructural relationship between the beneficial and detrimental impacts of grit blasting on the adhesion of thermal spray coatings.