Influence of surface character change of substrate due to heating on flattening behavior of thermal sprayed particles

The authors have confirmed that in the thermal spraying of practical powder materials, the splat shape changes with increasing substrate temperature to a circular disk shape from a fringe shape with splashing at a critical substrate temperature, T t . The increase of the substrate temperature may accompany a kind of essential change on the substrate surface, because the effect is maintained until the substrate is cooled down to room temperature. However, the nature of the substrate surface change due to the heating has not been clearly understood yet. In this study, AISI 304 stainless steel was used as a substrate material, and the substrate was heated in an air atmosphere or laser treated as a pretreatment. Substrate surface topography in nanometer scale was analyzed precisely by atomic force microscope (AFM). The relationship between surface topography in nanometer scale and splat morphology was discussed. Moreover, to evaluate the effect of chemical composition of the substrate surface, gold was coated onto the substrate surface by physical vapor deposition (PVD) after the heat treatment. The effect ofadsorbate/condensate on the substrate surface on the flattening behavior of thermal sprayed particles was also verified.