Synergistic effects of laser texturing and solid lubricants in Cr3C2-NiCr-(B2O3/Bi2O3) composite coating for enhanced tribological properties at 25 °C and 800 °C

Abstract

Cermet-based coatings exhibit excellent high-temperature wear resistance. However, their high-temperature lubrication performance is insufficient, which is likely to cause the friction pair materials to be severely worn. Herein, a novel Cr₃C₂-NiCr-(B₂O₃/Bi₂O₃) composite coating was developed by thermal spraying, laser texturing and high-temperature vacuum impregnation composite processes. Its tribological properties, elemental migration and synergistic lubrication mechanism were systematically investigated. The results show that the average friction coefficients of the composite coating are 0.17 and 0.08 at 25 ℃ and 800 ℃, respectively, representing reduction of 79 % and 83 % compared to the Cr₃C₂-NiCr coating, and exhibits excellent self-lubricating performance. Through in-depth analysis, a synergistic lubrication mechanism based on the migration of B/Bi elements is proposed: At elevated temperatures, B₂O₃ optimizes the friction interface as a low-viscosity glassy phase, while Bi₂O₃ reduces the shear strength via molten lubrication and the formation of Bi nanocrystalline films. B₂O₃/B₂O₃ composite lubricant provide excellent fluid lubrication at tribological interface. The mechanism originates from the dynamic coupling of low melting point migration, interfacial reaction and gradient film formation. B element enhances the interfacial bonding and thermal stability of the film through oxygen vacancy migration, while Bi element forms a plastic lubrication film via reduction and grain boundary segregation. The composite coating integrates long-term lubrication and anti-wear properties at high temperatures. These findings provide an innovative solution for the service life extension design of high-temperature moving components.