Numerical and experimental study on powder deposition mechanism of plasma sprayed YSZ-NiCoCrAlY coating

The YSZ-NiCoCrAlY thermal barrier coating system is a typical coating system for high-temperature protection of hot-end components. Analyzing its powder deposition behavior during plasma spraying and the evolution of the substrate surface can provide guidance for the industrial preparation of high-quality coating systems with excellent service performance. In this study, a metal-ceramic bilayer powder deposition model was established to explore the powder deposition behavior and substrate surface evolution. The results show that NiCoCrAlY particles form pie-shaped structures with a moderate degree of softening (i.e., moderate strain), while YSZ particles form crater-shaped structures with a higher degree of softening (i.e., greater strain). The overall tem-perature of the coating is primarily determined by YSZ particles, while the equivalent stress is mainly influenced by NiCoCrAlY particles. The differences in particle temperature, equivalent stress, and softening degree are related to their respective physical properties, such as thermal conductivity and thermal softening coefficient, among others. During the coating deposition process, multiple circular high-temperature regions and circular stress regions are generated on the substrate surface, primarily due to the impact of NiCoCrAlY bond-layer particles. The metal bond-layer serves to protect the substrate and reduce the impact of the subsequently deposited ceramic top-layer on the substrate. The comparison between the surface morphology and the porosity in the coating cross-section of the experimentally prepared coating validates the reasonableness and feasibility of the simulation work.