A finite element-based level set method for analyzing the effects of substrate conditions on ceramic splat generation in plasma spraying process

Abstract This paper deals with the simulation of a ceramic splat formation resulting from the impact, flattening, and solidification of a molten particle on a rigid substrate in plasma spraying conditions. The impact has a high velocity of up to 150 m s −1 . This process is the most crucial step in the coating’s generation. Therefore, it is crucial to investigate splat formation on a rigid substrate in order to have a better understanding of the microstructure of the ceramic coatings and improve their adhesion and cohesion, which are of primary importance for their effective performance. The simulation is carried out by resolving the conservation equations of mass, momentum, and energy. The ‘Level Set’ method is used to draw the interface between the molten particle and the surrounding gas. The numerical solution is based on the Finite Elements Method using a rectangular mesh. The effect of some substrate characteristics, such as material and initial temperature, on splat formation is analyzed, taking into consideration the effects of thermal contact resistance, wettability, and surface tension forces. It has been observed that substrate conditions, such as material and initial temperature, have a minor effect on the particle spreading, especially on the maximum spreading factor, ξ max , which varies somewhat between 2.93 for aluminum, 2.98 for stainless steel, and 3.06 for alumina. Moreover, the value of ξ max increases slightly with the substrate’s initial temperature from 2.95 for Ts = 300 K to 2.98 for Ts =700 K, while on the spreading time, no effect was observed; it is almost the same, t = 0.62 μs. On the other hand, these parameters, material and initial temperature, have a significant effect on the solidification time and, consequently, the splat formation; the solidification time is about 2.1 μs for the aluminum substrate, 3.4 μs for stainless steel, and 4.4 μs for alumina, while it’s of the order of 3.1 μs for a cold stainless steel substrate, Ts = 300 K, 3.25 μs for Ts = 500 K, and 3.4 μs for Ts = 700 K respectively. Furthermore, it was shown that the splat morphology is mainly related to the initial substrate temperature; by preheating the substrate, the particle breakup during the deposition may be limited, which helps to have splats with good adhesion to the substrate.