Coating technologies can improve mechanical components’ durability and lifetime by rebuilding the damaged surfaces. Surface restoration by coating is much more cost-effective than replacing the damaged component. Thermal spray is an effective coating technology for surface restoration. The thermal spray process involves the heated coating materials (e.g., ceramics, metal alloys, and metallic) being propelled onto the substrate as molten or semi-molten droplets to form a dense coating. However, material mismatches and extreme impact conditions can affect the quality of the coating. A deposition splat is desirable for obtaining a well-coated substrate surface during the thermal spray process. In the present study, the Smoothed Particle Hydrodynamics (SPH) method is employed to investigate the outcome of droplet impacts on substrates at thermal spray conditions. Various physical phenomena are simulated, including droplet behavior, heat transfer, and solidification; these phenomena are challenging to track and visualize experimentally. This work investigates the threshold of deposition splat of yttria-stabilized zirconia (YSZ) droplet impact under different substrate conditions. Two different substrate materials are considered, including YSZ and stainless steel. Numerical results are validated by experimental data obtained from the literature. The results show that the impact velocity and substrate temperature collectively determine the formation of the deposition splat. The splash occurs when the YSZ droplet impact velocity exceeds 437 m/s at substrate temperature 423 K. As the substrate temperature increases, the threshold of forming a deposition splat decreases slightly, resulting in an irregular splat morphology. The heat transfer effect is more pronounced at lower substrate temperatures, causing the droplet to solidify quickly. A regime diagram is proposed to characterize the outcomes of thermal spray impact in terms of the Sommerfeld parameter (K parameter) and substrate temperature. This study demonstrates the validity of the present SPH method for use in predicting and designing the thermal spray processes.

涂层技术可以通过重建受损表面来提高机械部件的耐用性和使用寿命。通过涂层进行表面修复比更换损坏的组件更具成本效益。热喷涂是一种有效的表面修复涂层技术。热喷涂工艺涉及将加热的涂层材料（例如，陶瓷、金属合金和金属）作为熔融或半熔融液滴推进到基材上以形成致密涂层。然而，材料不匹配和极端冲击条件会影响涂层的质量。为了在热喷涂过程中获得良好涂层的基材表面，需要沉积板。在目前的研究中，平滑粒子流体动力学 (SPH) 方法用于研究在热喷涂条件下液滴撞击基材的结果。模拟了各种物理现象，包括液滴行为、传热和凝固；这些现象很难通过实验跟踪和可视化。这项工作研究了不同衬底条件下氧化钇稳定氧化锆 (YSZ) 液滴撞击的沉积溅射阈值。考虑了两种不同的基板材料，包括 YSZ 和不锈钢。通过从文献中获得的实验数据验证了数值结果。结果表明，冲击速度和衬底温度共同决定了沉积片的形成。当基板温度为 423 K 时，YSZ 液滴冲击速度超过 437 m/s 时会发生飞溅。随着基板温度的升高，形成沉积飞溅的阈值略有降低，导致飞溅形态不规则。在较低的基板温度下，传热效果更明显，导致液滴快速凝固。提出了一个状态图，以根据 Sommerfeld 参数（K参数）和基板温度。这项研究证明了本 SPH 方法在预测和设计热喷涂过程中的有效性。