Effect of combination treatment on wear resistance and strength of Ti–6Al–4V alloy

This study was conducted to comprehensively investigate the effect of combination treatment on the wear resistance, mechanical properties, and fatigue strength of Ti–6Al–4V alloy. The combination treatment was composed of plasma nitriding, short-time duplex heat treatment (hereafter, duplex heat treatment), and fine-particle bombarding (FPB). A hardened layer was formed by plasma nitriding. The substrate was strengthened by duplex heat treatment. The brittle compound layer, formed by plasma nitriding, was eliminated by FPB, and also high compressive residual stress was introduced. Wear resistance was improved by combination treatment; however, hybrid surface treatment, composed of plasma nitriding and FPB, was more effective to improve wear resistance than combination treatment. The tensile strength was improved 30% by combination treatment. Fatigue crack initiation from the surface was strongly suppressed by the formed layer and introduced high compressive residual stress. Moreover, subsurface crack initiation was suppressed by the strengthened substrate. As a result, fatigue strength was greatly improved, by 59%, by the combination treatment.