Microstructure, properties and tribological behaviors of TiNbZr refractory medium-entropy alloy coating fabricated on the Ti6Al4V substrate by laser cladding

• Published in: Surface & coatings technology Vol. 512; p. 132317
• Main Authors: Liu, Jin, Han, Ruipeng, Liu, Yan, Chen, Jingqing, Zhao, Yongsheng, Hu, Dengwen, Yang, Chuan, Wang, Lei, Chen, Hui
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2025
• Subjects: Glaze layer; Refractory medium entropy alloy; TiNbZr; Tribological; TiNbZr; Refractory medium entropy alloy; Tribological; Glaze layer
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2025.132317

In order to enhance the wear resistance of the Ti6Al4V alloy at both room temperature (RT) and elevated temperature, thereby promoting the lightweight application of titanium alloys in high-speed train braking systems, a TiNbZr refractory medium-entropy alloy (RMEA) was deposited on the surface of the Ti6Al4V substrate by laser cladding. Subsequently, the tribological behavior of the TiNbZr RMEA coating and the Ti6Al4V substrate was analyzed at RT and 700 °C. The phase, microstructure and wear mechanism of the TiNbZr RMEA coating and the Ti6Al4V substrate were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and X-ray photoelectron spectroscopy (XPS). The findings indicate that the TiNbZr RMEA coating is a single-phase body-centered cubic (BCC) disordered solid solution, exhibiting high strength, plasticity and high bonding strength. The tribological behavior demonstrates that the TiNbZr RMEA coating exhibits excellent wear resistance at both RT and elevated temperatures. This can be attributed to the fact that the Ti6Al4V substrate is predominantly subjected to abrasive abrasion, whereas the TiNbZr RMEA coating is subject to a combination of abrasive mechanisms, including adhesive and oxidation abrasion. In the repeated friction process, the oxides (TiO₂, Nb₂O₅, ZrO₂, and CuO) and material transfer (Cu, Fe, and Cr from the friction pair) on the surface of the TiNbZr RMEA coating sinter together to form a “glaze layer”. This layer acts as a lubricant and barrier, reducing the coefficient of friction (CoF) and significantly improving wear resistance. •Laser-clad defect-free BCC RMEA coatings on titanium alloys exhibit high bonding strength and uniformity.•Superior room-temperature plasticity vs. conventional refractory high-entropy alloys (RHEAs).•Self-lubricating glaze layer on TiNbZr RMEA reduces friction and wear rates.