Effect of shot-peening treatment on the bio-tribological properties of a Ni+ implantation layer formed on the surface of Ti6Al4V

To improve the bio-tribological properties of the Ti6Al4V surface, the Ti6Al4V alloy was subjected to a shot-peening treatment and a subsequent Ni+ implantation process. The phase composition, phase content and grain size of the resulting Ni+ implantation layer formed on the surface were evaluated via x-ray diffraction. The nano-hardness of the modified layer was measured with a nano-micro mechanical probe. Moreover, after bio-tribological testing, the scratch morphology of the layer was observed with a scanning electron microscope. The results revealed that this layer was composed mainly of Ti2Ni. The shot-peening pretreatment yielded a significant increase in the Ti2Ni content and the nano-hardness of the layer, resulting in grain size refinement of the formation phase. When a Ni+ implantation energy of 45 keV was employed, the Ti2Ni phase content and the grain size of the shot-peened layer increased by 33.6% and decreased by 65.9%, respectively. The corresponding friction coefficients under artificial saliva and a sodium hyaluronate pure water solution decreased by 20.9% and 29.3%, respectively. In the case of samples implanted at an energy of 40 keV, the nano-hardness of the shot-peened layer was 50.8% higher than that of the non-peened layer. Therefore, a shot-peening pretreatment can yield a significant improvement in the properties of the single Ni+ implantation layer on the Ti6Al4V surface.