Characteristics of Mo–Cr duplex-alloyed layer on Ti6Al4V by double glow plasma surface metallurgy

Abstract

To improve the wear resistance, a Mo–Cr alloyed layer is prepared on the surface of Ti6Al4V by double glow plasma surface metallurgy. The microstructure and phase constituents of the Mo–Cr alloyed layer are characterized by analyses of SEM and XRD. The results indicate that the alloyed layer is composed of a deposited layer and a diffused layer with thickness of 10μm and 12μm respectively. The modified layer is homogeneous and dense. In the diffused layer the contents of Mo and Cr distributed decreasingly with the depth increasing. Microhardness and nanoindentation tests were carried out to evaluate the mechanical properties of the alloyed layer. The surface hardness reaches 1309HV0.01, and also decreases gradually with the depth increased. The nanoindentation tests show that the alloyed layer has a much smaller displacement and larger elastic modulus than that of the substrate. The tribological behaviors of Mo–Cr duplex-alloyed samples and bare substrate were investigated using a ball-on-disk tribometer under the conditions of lubrication-free at room temperature. Comparing to the substrate, the Mo–Cr alloyed specimen records a lower friction coefficient. The wear mass of Mo–Cr alloyed layer is just 1% of the bare substrate. All the results indicate that the Mo–Cr duplex-alloying has effectively improved the wear resistance of Ti6Al4V.