Tribological Performance of Laser‐Clad Co‐Based Alloy Coatings on Brake Discs at Elevated Temperatures

Co‐based alloy coatings were fabricated on high‐speed train brake discs using an optimized laser cladding process. The microstructure, hardness, and tribological properties of the coatings were systematically investigated at room temperature, 400°C, and 800°C. The results indicate that the coating exhibits a dense, uniform microstructure with excellent metallurgical bonding to the substrate, and its average microhardness reaches 545.8 HV 0.3 , approximately 1.4 times that of the substrate. The coating consistently demonstrates a lower friction coefficient than the substrate across all temperatures. Notably, its wear rate decreases with increasing temperature—a trend opposite to that of the substrate—and at 800°C, the coating's wear rate is only 29% of the substrate value. Analysis of the wear mechanisms reveals a transition from abrasive wear at room temperature to adhesive and oxidative wear at elevated temperatures. The outstanding high‐temperature performance is attributed to the coating's stable γ ‐Co matrix and the formation of a protective oxide layer. This study demonstrates that the laser‐clad Co‐based coating is a highly promising surface solution for enhancing the service life and braking reliability of high‐speed train brake discs under extreme thermal conditions.