Microstructure Characteristics and Wide Temperature Range Tribological Properties of Ti6Al4V Laser Modified Surface by Remelted

A two-step approach toward creating hard, wear-resistant layer on Ti6Al4V was conducted. Laser remelting process was applied on the in-situ formation of nitirided Ti(N) layer and oxynitrided Ti(N,O) layer on Ti6Al4V that was prepared by the laser gas-assisted processing, resulting Re-Ti(N) and Re-Ti(N,O) displayed the relatively uniform hierarchy, respectively. The results revealed that, Re-Ti(N) layer had the composite structure comprised of nitrogen-rich αˊ-Ti and TiN_x, while Re-Ti(N,O) layer had a highly specific heterogeneous structure composed of nitrogen and oxygen-rich αˊ-Ti, TiN_xO_y. As compared with Ti6Al4V, the hardness, elastic modulus and wear resistance of Re-Ti(N) and Re-Ti(N,O) increased by 2 times. In comparison with Re-Ti(N) layer, the introduction of oxygen not only enabled refining the crystalline structure and promoting the mechanical strength of Re-Ti(N) layer significantly, but also inhibited the happening of adhesive wear between the sliding contact; neverthless the friction remained relatively higher regardless of the surface processing over Ti6Al4V. According to the analysis of wear debris collected from the friction testing, the high dislocation density and defects induced by plastic deformation during friction were figured out to be the crucial factors for the wear mechanism of Ti6Al4V before and after surface process. Evolution of the frictional behavior Ti6Al4V before and after laser processing was further clarified on the basis of the microstructural transformation and thermal properties of Ti6Al4V against the counterpart.