For solid particles impacting on to a substrate, both the particle and the substrate plastically deform to allow intimate interfacial bonding. In the process of plastic deformation, some of the particle’s kinetic energy is converted into heat and strain energy. However, the heat generated during the impact process is not considered sufficient to melt or thermally soften the impacting particles.

In this study, Ni-chrome alloy particles were thermally sprayed onto a variety of substrate materials using the high velocity air fuel (HVAF) technique. Although the various substrate materials were sprayed using identical powder material and thermal spray conditions, the type of splat morphologies and the amount of different types of splat morphologies varied significantly for different substrate materials. Predominantly solid particles are observed penetrating deeply into softer substrates such as aluminium whereas molten splats were observed in harder substrates which resisted particle penetration.