Microstructure And Mechanical Properties Of The Ni-B-Ti Composite Coating On Ta2 Prepared By Pre-Plating And Laser Remelting

To improve the mechanical properties of TA2, a Ni-B-Ti composite coating on TA2 was synthesized by a two-step surface modification method. Firstly, a Ni-TiB2 pre-coating was electroplated on TA2; subsequently, the pre-coating was remelted by laser beam to synthesize the composite coating. Microstructure analysis reveals that: i) the composite coating shows the obvious phenomenon of phase stratification, TiNi and Ti 2 Ni phases occupy the top and bottom layer of the coating, respectively; ii) high aspect ratio TiB whiskers are formed in the composite coating; iii) good metallurgical bonding of the coating with the substrate is obtained. Nanoindentation tests indicate that the presence of TiB increased the hardness of the composite coating to as high as 9.07 GPa, which is about 3.4 times higher than that of TA2 substrate (2.08 GPa), and about 1.6 times higher than that of the coating without any reinforcement (3.51 GPa). The wear test results show that although the coatings have higher friction coefficients than TA2 substrate, the wear rate of the composite coating is 88.9% and 29.8% lower than that of TA2 substrate and the coating without any reinforcement respectively, indicating that the wear resistance of the coatings has been greatly improved, and the presence of ceramic reinforcement intensifies the increase of wear resistance of the coating.