Optimization and Tribological Evaluation of Plasma-Sprayed Cr3C2 and Stellite Coatings on Inconel 625 using Taguchi-ANOVA Method

Superalloys used in aerospace and power generation industries are frequently exposed to severe thermal and tribological conditions, resulting in significant wear loss. In this study, carbide-based Cr3C2 and Stellite coatings were deposited on Inconel 625 substrates using the Atmospheric Plasma Spray (APS) process to improve wear resistance. The microstructural characteristics, hardness, friction, and wear behaviour of coated and uncoated specimens were systematically evaluated. SEM analysis revealed uniform coating deposition with strong interfacial bonding and no visible pores or microcracks. EDAX results confirmed the presence of major alloying elements, including nickel, chromium, and carbon in Cr3C2 coatings, while Stellite coatings showed high chromium and carbon content. The plasma-sprayed Cr3C2 coating increased the surface hardness from 505 HV for the uncoated Inconel 625 substrate to 720 HV, corresponding to a 42.6% increase, while the Stellite coating achieved 669 HV, representing a 32.5% increase. The Cr3C2 coating exhibited the lowest wear loss of 0.2% and the minimum specific wear rate at 200 °C, indicating superior tribological performance under elevated-temperature conditions. Compared with the uncoated substrate, both coatings significantly reduced the specific wear rate, with the Cr3C2 coating demonstrating the greatest improvement in wear resistance. Taguchi L9 and ANOVA analyses confirmed coating type as the most influential parameter affecting wear performance.