In this study, single splats of polyether ether ketone were plasma sprayed onto aluminum substrates that had been boiled, etched, or polished and then thermally treated, except for one etched substrate, to remove water from the surface. Splat morphology was viewed in a scanning electron microscope and splat-substrate interfaces were examined using TEM and focused ion beam imaging. The results show that PEEK splats have a poor level of contact on aluminum substrates that were boiled and those that were etched but not thermally treated. In contrast, specimens that had undergone thermal treatment to minimize the presence of water on the substrate surface exhibited high levels of contact at the splat-substrate interface with significantly less porosity.

In this study, aluminium 5005 and stainless steel 304L substrate surfaces were modified by thermal and hydrothermal treatments. Ni-Cr single splats were deposited onto these substrates at room temperature using plasma spraying. The collected splats were characterised qualitatively and quantitatively by Scanning Electron Microscopy (SEM) and ImageJ software. A splat classification scheme was developed based around splash and disk-type splats. The proportions of the different splat types were found to vary significantly as a function of substrate pretreatment, especially when the pretreatment involved heating. The effect of surface roughness to splat formation and splat shape was investigated. It was observed that surface roughness was not a critical factor in splat morphology. The above substrate surfaces were also characterised by X-ray photoelectron spectroscopy (XPS) using in-situ heating in vacuum to determine the effect of thermal pretreatment on substrate surface chemistry and the oxide thickness. It was found that heat treatment promoted a change in the chemical structure of the oxide surface layer which was consistent with the dehydration of oxyhydroxide to oxide. Dehydration of the substrate surface layer improved the physical contact between the splat and substrate which enhanced the formation of disk-splats, decreased the number of pores evident in the splats and increased number of splats and their diameter.