Recent developments in HVOF coatings: a comprehensive review on microstructure, adhesion, and wear behavior

Elements that operate in harsh environments in power generation, marine, and aerospace systems are often subjected to surface erosion, wear, and corrosion from solid particles, silt, cavitation, and slurry. To reduce such deterioration, carbide-based materials are widely used due to their exceptional chemical stability and hardness. Such carbides can readily be used as protective coatings on components with critical features using advanced thermal spray technologies, such as HVOF (high-velocity oxy-fuel) and HVAF (high-velocity air fuel) plasma spraying. Carbide thermal spray coating is mainly made of chromium carbide (Cr3C2), tungsten carbide (WC), or a combination of both. The overall behavior of these coatings, however, is highly dependent on the carbide composition and type, binder content, and spray process parameters. This paper provides a critical analysis of degradation processes and the efficiency and effectiveness of different carbide-based coating materials, including various carbide grain sizes, binding types, and process parameters, across different working conditions. There is also a shift towards post-processing techniques to further enhance coating performance by modifying its microstructure. A detailed explanation of the processes that occur after treatment, including cryogenic, laser, and heat treatments, is also provided to underpin their contribution to the coating’s increased durability and functionality.