On the surface preparation of nickel superalloys before CoNiCrAlY deposition by thermal spray

This work is dedicated to the study and the characterization of the surface of nickel superalloys before the deposition of the MCrAlY (MCo, Ni or both) bond coat. Our aim is to determine the factors (roughness, contamination and others) that lead to the best properties of the coating in terms of adhesion. We used MAR M247 samples as substrates. Different preparation treatments were considered: dry and wet blasting by corundum with different grain size distribution, dry blasting by silicon carbide and cleaning by solid carbon dioxide. In general, we observed that the highest roughness led to the best adhesion as measured by critical load tests. However, this parameter must be balanced against known problems related to the use of coarse abrasive powders.