Papers by Keyword: Splat Formation

Abstract: A plasma-sprayed coating is built up by the layering of individual splats. The latter are formed by spreading and solidification of molten particles sprayed onto a solid substrate. The coating properties depend on its microstructure and the quality of contact between the splats and the underlying layer and between the piled-up splats. This work deals with a 1D model of heat transfer between plasma-sprayed alumina splat and smooth substrate. The model is based on heat diffusion in the solidifying splat and substrate and includes undercooling phenomenon, heterogeneous nucleation and crystal growth kinetics. It assumes that splat spreading and solidification are two independent processes. The model predicts splat cooling and solidification taking into account, as far as possible, the in-flight particle properties drawn from the literature in order to study their effect on splat thermal history. The effect of the quality of contact between the splats as well as the already-deposited and solidified layer thickness on the grain size distribution and front solidification velocity is investigated.

Abstract: Splat morphologies of YSZ/NiCrCoAlY TBCs by plasma spray were characterized using SEM. Based on some assumptions, plasma jet temperature field was established by numerical simulation and the effects of spray parameters are individually studied to optimize the spray process parameters. Furthermore, the interaction wetting ability was taken into account in order to investigate the interaction effect between ZrO2 and NiCrCoAlY droplets. It shows that T enhances markedly with increasing in I and decreasing in FAr; while in despite of the insignificant effect of FHe on T, the temperature of powder in plasma jet enhances with increasing in FHe. As a result of higher thermal conductivity of powder in He plasma gas. NiCrCoAlY droplet impacting solidified NiCrCoAlY splat wets well and spreads fluently while that impacts solidified YSZ splat spreads restrictedly for the poor wetting on the YSZ splat surface.

Abstract: There is a growing interest in use of the nickel-based alloy Inconel 625 coatings due to its ability to improve base materials high temperature properties. Thermal spraying methods such as Air Plasma Spraying (APS) can be considered as a convenient method to deposit this material. The present work deals with APS deposited Inconel 625 structures consisting of huge number of individual splats formed by impacting molten droplets on substrates during spraying process. It is clear that the splat formation mechanism which dominates its size, cohesion, and boundaries highly influences the microstructure of the coating. This paper presents a developed numerical technique performed to simulate splat formation using a three dimensional model. In this method flow field is solved by Finite Volume Method (FVM) and free surfaces are determined from Youngs’ Volume of Fraction method (VOF). Finally, the model prediction is correlated with the actual splat geometries.