Ankur Gill, Vikas Chawla, Amit Handa, Santosh Kumar
The accelerated degradation of energy infrastructure components functioning in an extreme service environment is one of the key issues for long-term reliability and safety. Carbide-reinforced thermal spray coatings are widely used as protective solutions; nevertheless, their behavior under combined thermal, erosive, and corrosive stresses is of high variability, and the mechanisms of degradation are not yet fully understood. Key unsolved scientific issues include the interplay between erosion and oxidation across a range of temperature regimes, why conflicting erosion-corrosion (E-C) trends are often reported for similar coating systems, and what microstructural features fundamentally control coating stability at high temperatures. This critical review is a synthesis of recent advances in understanding the high-temperature E-C behavior of carbide-reinforced coatings by systematically examining deformation mechanisms, including particle-impact erosion, oxide-scale formation/spallation, carbide dissolution, and interface-controlled failure. Further, emphasis is placed on the roles of carbide chemistry, binder composition, microstructural integrity, and thermal spray processing routes in determining regime-dependent performance. The shortcomings of current methods for quantifying E-C synergy are critically reviewed, and mechanistic models are proposed to reconcile the varying results in the published literature. Based on this synthesis, key research gaps are identified, including the need to design oxidation-resistant binders, improve control of carbide stability during deposition, conduct long-term performance assessment at service-relevant temperatures, and develop predictive models of E-C regimes. Overall, this review provides a roadmap for the rational design of next-generation protective coatings for metals and alloys subjected to extreme high-temperature environments.