Depth-sensing indentation for assessing the mechanical properties of cold-sprayed Ta

The stress-strain behaviour of cold-sprayed Ta coatings, deposited onto Al and steel substrates, was studied by depth-sensing spherical and sharp (Berkovich) indentation testing, and was compared to that of an annealed Ta sheet. The mechanical properties of the coatings, free of any scale-dependence, are insensitive to the presence of a lamellar structure, indicating strong, tight bonding between cold-sprayed Ta particles. Accordingly, the coatings are isotropic. The stress-strain curves reveal that the coating material experienced some degree of work-hardening during cold-spraying; indeed, the sprayed particles were plastically deformed at impact. This was confirmed by line profile analysis on XRD patterns. The consistency between the results from different indentation testing techniques provides a means to cross-validate the entire analysis.