Tuning plasma jet parameters for enhanced ceramic composite coatings: A comprehensive review of microstructure, performance, and applications

This systematic review critically evaluates the influence of plasma jet parameters on the deposition, microstructure, and functional performance of ceramic composite coatings, with a specific focus on thermal barrier and wear-resistant applications in the aerospace and energy sectors. A total of 145 peer-reviewed articles published between 2005 and 2024 were analyzed, of which 138 were directly cited in this review. The analysis encompasses key plasma spray techniques including Atmospheric Plasma Spraying (APS), Suspension Plasma Spraying (SPS), and Plasma Transferred Arc (PTA). Process parameters such as arc current, plasma gas composition (e.g., Ar/H₂, Ar/He), stand-off distance, and feed rate were found to strongly influence in-flight particle behavior, deposition efficiency, and coating quality. Higher enthalpy plasma (Ar/H₂) enhanced particle melting and coating density, while reduced stand-off distances generally improved adhesion and hardness. Microstructures varied from lamellar and columnar (YSZ, Al₂O₃) to dendritic eutectic networks, with porosity levels ranging from < 2 % to ∼15 % depending on the technique and settings. Optimized plasma parameters consistently yielded coatings with lower porosity, higher mechanical strength, improved thermal shock resistance, and extended durability under thermal cyclic fatigue and burner rig tests. Conversely, deviations from optimal conditions led to increased porosity, microcracks, and phase instability. The review concludes that precise plasma jet parameter control is pivotal for tailoring ceramic coating properties. Future research should integrate machine learning, real-time diagnostics, and standardized testing protocols to enhance process reliability, reproducibility, and scalability across industrial platforms.