The Role of Substrate Surface Chemistry on Splat Formation During Plasma Spray Deposition by Experiments and Simulations

NiCr single splats were plasma-sprayed on aluminum and stainless steel substrates, which were modified by immersion in boiling water, to grow specific types of oxide/oxyhydroxide on the surface. It was observed that there was no splat formation on aluminum substrate. In contrast, a significant number of splats were formed on stainless steel substrate. The differences in splat formation on aluminum and stainless steel surfaces corresponded to the variations of thickness and proportions of the oxide/oxyhydroxide layer on the surfaces. A three-dimensional numerical model was developed to simulate the impact of a droplet onto the substrate. The simulation illustrated good agreement with experimental observations. The effect of the oxide layer on the splat morphology was also examined. It was suggested that the splat morphology was more strongly influenced by water release from the dehydration of oxyhydroxide to oxide rather than by simple presence of the oxide layer on the substrate surface.