From wear to lubrication: mechanistic insights into multi-stage wear evolution in Ni-WC/MoS2 composite coatings

• A predictive model for the coefficient of friction and wear rate was developed through Box-Behnken response surface optimization of laser cladding parameters. • Investigating wear modes and self-lubricating behaviors at various stages using wear duration as the variable. • A four-stage wear evolution process was revealed, progressing from initial abrasive wear to a lubrication-dominated steady-state regime. • Ultrasonic vibration-assisted laser cladding enhances coating homogeneity and accelerates tribolayer formation. Ni-WC/MoS 2 composite coatings were fabricated on 65Mn steel via laser cladding using Ni60@WC and Ni@MoS 2 powders. Process parameters were optimized via Box-Behnken design, identifying optimal conditions: 19.3 wt% Ni@MoS 2 , 975 W laser power, 4 mm/s scan speed. The coating formed a stable MoS 2 -dominated lubricating layer mechanically supported by WC particles, significantly reducing friction and wear. Further analysis revealed a four-stage wear evolution transitioned from abrasive wear to a stable low-wear regime. Morpho-compositional analyses revealed synergistic lubricant release, hard-phase distribution, and tribolayer formation. Ultrasonic vibration assistance enhanced coating homogeneity, accelerated lubricant formation, reduced residual stress, and improved tribological performance. These findings offer theoretical and practical guidance for the design and fabrication of high-performance self-lubricating wear-resistant coatings