TiN/Al Composite Coating In-situ Generation Technique On Titanium Alloy Surface And Erosion Resistance

In this study, a TiN/Al hard composite coating was produced successfully on the surface of titanium alloy through using laser nitriding and synchronous feeding powder technology. The microstructure and phase composition of the composite coating in different process parameters were studied. Then we measured the micro-hardness and wear resistance of the composite coating. Finally, the research was mainly focused on the erosion resistance of the composite coatings. The erosion mechanism of the composite coatings was discussed according to the surface figure and coatings mass loss. The main contents are as follows:(1)A TiN/Al hard composite coatings with crack-free was in-situ generated successfully through the laser alloying technology and synchronous feeding powder process, and effectively solved the problem of laser nitriding layer cracking.(2)The composite coating was mainly made up of the dendrite-shaped nitride phase. The laser power and the laser scanning speed had a significant influence on the development of the nitrides in the composite coating, but the nitrogen flow rate had less influence. With the XRD phase analysis, we found that the main phase of the composite coating was TiN and Al. In the optimization of process parameters conditions, these two phases are evenly distributed all over the coating.(3)The composite coating could obviously increase the surface hardness and wear resistance of matrix material, and the TiN phase played an essential role. The wear mechanism of the composite coating is mainly abrasive wear. There are also a little adhesion wear and peeling-off wear with fatigue.(4)The composite coating had better erosion resistance than matrix material. The laser power and the laser scanning speed had an important influence on the erosion resistance of the composite coating. Erosion angle had also a certain influence on the erosion resistance of the composite coating. Result from erosion test, the composite coating showed brittleness erosion mechanism, meaning that coating mass loss should increase with the increasing erosion angle. It is concluded that the main erosive mechanism of the composite coating was brittle fatigue fracture and micro-cutting.