Indentation of metallic and cermet thermal spray coatings

Indentation methods are presented by which the elastic and inelastic stress-strain characteristics of metallic thermal spray (TS) coatings on substrates may be extracted. The methods are based on existing techniques for brittle solids, and adapted for the finite geometry associated with coatings. Basic assumptions and derivations are given, along with guidelines for experimental measurement. Using these, indentation inelastic stress-strain curves are generated for NiCrAlY and Ni-Al bondcoats, as well as WC-Co cermet coatings. Elastic moduli are extracted for CoNiCrAlY coatings. Results are briefly discussed in the context of the effect of feedstock material, process and post-process heat treatment on the intrinsic properties of splats as well as their in-coating cohesion. The methods presented are attractive, particularly for the TS industry, due to the minimal specimen preparation and lack of intricate equipment required for measurement.