In-situ synthesis of TiNiTa coating by laser cladding with orthogonal test method

In this paper, we focus on the optimized process parameters of the TiNiTa shape memory alloy functional coatings prepared by laser cladding technology on the Ti6Al4V (TC4) alloy, and studied properties. On the basis of orthogonal experiment, the optimum process parameters of TiNiTa coatings were determined as follows: the laser power was 100 W, the scanning rate was 2.5 mm/s, the defocusing amount was 10 mm, the pulse width was 5 ms, and the frequency was 10 Hz. The influence of laser power, scanning speed and defocus amount on the hardness of cladding layer was evaluated by the range analysis from the experimental data. The results show that the range of defocusing amount, scanning speed and laser power were R1 = 34, R2 = 14.334, R3 = 44.334, respectively. Therefore, the degree of influence on the process parameters on the quality of the prepared TiNiTa coating was determined in the following order: defocus amount, laser power, scanning speed. When the energy density was 1698 J/mm2, the microstructure of the cladding layer was compact and fine, and the metallurgical bond with the matrix was formed. In addition, the polarization potential and the electrochemical impedance spectrum (EIS) radius of the cladding layer were firstly increased and then reduced with the increase of the energy density. It can be seen that the corrosion resistance of TC4 titanium alloy surface was significantly improved. XRD results shows that the cladding layer was mainly composed of B2 parent phase, B19′ martensite phase and Ti2Ni phase. The results indicate that energy density was an important factor affecting the structure and properties of cladding layers. Through the above analysis, the combination of orthogonal test and range analysis provides an efficient and reliable method to select and optimize the technological parameters of laser cladding.