Effect of transition metals (Nb, Ta, and V) doping on the high-temperature mechanical and tribological properties of CrYN coatings

This study focused on developing a high-temperature tribological coating for AISI 316L stainless steel. CrYN coatings doped with transition metals such as niobium, tantalum, and vanadium (Me-CrYN) were deposited using a closed-field unbalanced magnetron sputtering (CFUBMS) system. In a previous study, the Taguchi L9 orthogonal array design was employed to optimize the deposition parameters based on tribological performance under dry sliding conditions at room temperature. Among the nine experimental runs, the three coatings exhibiting the lowest friction coefficients and highest wear resistance were selected for high-temperature tribological testing. In the present work, these three optimized Me-CrYN coatings were systematically evaluated for their tribological and adhesion properties at elevated temperatures. High-temperature tribological performance was assessed using a pin-on-disc tribometer in ambient air at 450 °C, 550 °C, and 650 °C, with particular attention given to their frictional behavior. Additionally, adhesion strength was evaluated at room temperature via scratch testing, both on the as-deposited coatings and those subjected to high-temperature tribological testing at 450 °C, 550 °C, and 650 °C. The results demonstrate that the Me-CrYN coatings maintain tribomechanical stability at elevated temperatures, with hardness values ranging from 8.8 to 15.3 GPa. Nb-doped coatings exhibited a reduction in friction from ∼0.55 at room temperature to ∼0.30 at 650 °C (≈45 % decrease), while Ta-doped coatings maintained stable values around 0.40 across all temperatures (<5 % variation). In contrast, V-doped coatings showed an initial rise from ∼0.13 at room temperature to ∼0.30 at 450 °C (≈115 % increase), but then decreased to ∼0.10 at 550 °C (≈25 % below RT) and ∼0.12 at 650 °C (≈10 % below RT). Adhesion strength was preserved after thermal exposure, supporting their potential for high-temperature applications.