Taguchi-based optimization and surface characterization of AISI 420 and CR12 steels under solid particle erosion and NiCrAlY coating protection

Erosive wear is a major cause of material degradation in high-velocity and high-temperature industrial environments. Understanding how impact parameters such as temperature, velocity, and impingement angle interact is essential for improving component lifespan. This study evaluates the erosive behaviour of AISI 420 and CR12 steels using a Taguchi L9 design combined with ANOVA, mass loss measurements, roughness analysis, and FESEM–EDX characterisation. Velocity was identified as the dominant factor, contributing 81.61% (AISI 420) and 85.80% (CR12) to erosion variability, followed by angle and a non-linear temperature response. AISI 420 showed ∼35% lower average mass loss than CR12, while CR12 exhibited ∼48% higher loss under the most severe condition (600 °C, 30°, 100 m/s). Morphology and roughness trends confirmed cutting-dominated wear at shallow angles and oxide-assisted degradation at high temperatures. A NiCrAlY coating, applied via HVOF at the optimum condition, significantly reduced erosion severity, minimised groove formation, and stabilised surface roughness. This integrated Taguchi–mechanistic study highlights the critical role of impact parameters and demonstrates the protective effectiveness of HVOF-sprayed NiCrAlY for high-temperature, particle-laden applications.