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

NiCr single splats were plasma-sprayed at room temperature on aluminum and stainless steel substrates which were modified by hydrothermal treatment in de-ionised water for 30 minutes. It was observed that there was no splat formation on aluminum substrate. In contrast, a significant number of disk splats were formed on stainless steel substrate. The differences in splat formation on aluminum  and stainless steel substrates corresponded to the different thickness of the oxide and oxyhydroxide layer on the substrate surface. A three-dimensional numerical model was developed to simulate the impact of a molten splat onto the substrate. The simulation illustrated good agreements with those obtained from the experiments. The effect of oxide and oxyhydroxide layer on the splat morphology was also included in the model. It was concluded that the splat morphology was strongly influenced by water release from the dehydration of oxyhydroxide rather than the oxide layer on the substrate surface.