Titanium Alloy Surface Laser In Situ Synthesis Tin / Ti <sub> 3 </ Sub> Al Coating Microstructure And Mechanical Properties

Laser cladding is an advanced method for synthesizing high-performance and multi-function coating, which is based on rapid solidification. The TiN/Ti₃Al composite coating was prepared on Ti6A14V alloy surface by laser in-situ synthesis method, and the chemical reaction between A1N and Ti under the high temperature was studied. Moreover, the microstructure and mechanical properties of composite coating was analysized, aiming to provide theoretical basis and certain technology foundation, and improving the abrasion resistance and high temperature oxidation resistance properties of titanium alloy.In this paper, the effects on macro-morphology under different molar ratio and laser powder density were analysized by using somatotype microscope. The phase qualitative and quantitative analysis of composite coating under different technological parameter was characterized by X-ray diffraction (XRD).The microstructure feature was characterized by scanning electrical microscope and energy (EDS).The microhardness of samples section was tested by microhardness instrument.The macro-morphology analysis displayed that the composite coating surface taked on different scale fusion defects when the molar ratio is 4:2,but that presented a full fusion when molar ratio is 4:1 and the laser power density is 1.528x10⁴W·s·cm^-2, and no pores and cracks.XRD qualitative analysis results confirmed that the phase species is nothing to do with the molar ratio and laser powder density, and the phase is composed of TiN and Ti₃A1.The phase quantitative analysis results also indicated that the contents of TiN phase and Ti3_A1 phase and the lattice constant was changed regularity with the increase of laser power density. These results illustrated that the non-equilibrium phase was produced in the coating. Although the stoichiometric ratio of prepared powder strayed from the theoretical value, the coating phase was also composed of TiN and Ti₃AI.SEM and EDS analysis results indicated that the microstructure was closely connected with the molar ratio and laser powder density. The TiN phase mostly appeared three kinds of morphology, namely granule-like, rod-shape and fine-dendrite, and the Ti₃A1 phase is needle-like. Moreover, the morphology of TiN phase changed gradually dense, and from granule-like to rod-shape.The microhardness of test samples cross section results showed that it presented a good transition from substrate to coating surface. The average microhardness of the coating changed with the increase of laser power density, and the maximum scale arrived at 844 HVo.2·The increasement of microhardness is benifical to the improvement of the titanium alloy abrasive resistance.