Enhanced Wear Resistance of Ti-7.5Nb-4Mo-2Sn Shape Memory Alloy via Optimized Ti-Sn Coating Design and Laser Cladding

This study addressed the poor wear resistance of Ti-7.5Nb-4Mo-2Sn shape memory alloy through the development of Ti-xSn (x = 6, 8, 9, 10, 20 at.%) coatings and laser cladding technology. This β-type titanium alloy is a promising biomaterial for artificial joints and bone fixation implants, and laser cladding is a superior surface modification technology for fabricating metallurgically bonded high-performance coatings. Microstructural characterization revealed that increasing Sn content from 6% to 10% progressively suppressed β-phase formation while enhancing microhardness (peak value: 430.06 HV1) and wear resistance. Conversely, further Sn addition of 20% degraded these properties. The optimal Ti-10Sn alloy was subsequently laser cladded onto a Ti-7.5Nb-4Mo-2Sn substrate in the form of pre-placed thin sheets under varying laser scanning speeds (7–13 mm/s). The results indicated that processing at 10 mm/s produced superior coating features, including complete metallurgical bonding (20 μm transition layer), the maximum surface hardness (494 HV1, 93% increase), and superior wear resistance. Microscopic analysis confirmed a wear mechanism transition from mixed adhesive–abrasive wear (7.5Nb-4Mo-2Sn substrate) to pure abrasive wear (Ti-10Sn coating), resulting in the enhanced wear resistance of the substrate. This study demonstrated that synergistic alloy design combined with a laser cladding approach can significantly enhance biomedical alloy performance.