TiN/Al Composite Coatings Produced By Laser Surface Alloying And Analysis Of The Properties

According to the excellent high strength-to-weight ratio and corrosion resistance, Ti6A14V is an attractive material for the last stage blade of a steam turbine. Liquid impact erosion is one of the major causes of turbine blade failure. Protecting the Ti6A14V blade surface with erosion resistant coating is one of the feasible solutions to overcome this superficial damage results from liquid impact. Aiming at the problem of the laser alloying technology, a TiN/Al hard composite coating is produced at the surface of the titanium alloy substrate through the method of adding alloying elements and optimizing the process parameters. This composite coating has excellent performance and this method effectively solved the problem of laser nitriding layer cracking. Then the micro structure and performances of the composite coating in different process parameters is studied through SEM morphology observation, XRD phase analysis. Finally, we measured its micro hardness、Preliminary studied its mechanical properties. the main contents are as follows:(1) A TiN/Al hard composite coatings with pore-and crack-free were successfully fabricated through the laser alloying technology combining the plasma spraying technology. It was shown that adding alloying elements is an effective approach to avoid the coating from cracking in laser alloying process.(2) This composite coating is main make up of the the nitride phase and the Ti-Al intermetallic phase, the laser power and the laser scanning speed have a significant influence to the developing of the nitrides, but the nitrogen flow rate has less influence. In the optimization of process parameters conditions, this two phase are evenly distributed all over the coating.(3) Hardness and wear test is implemented on the laser alloying composite coating and the impact of laser parameters on hardness and wear resistance is recorded and analyzed.The results show that the increase of laser power, the decrease of scanning speed, the increase of nitrogen flow rate lead to the increase in hardness and wear mass loss of the coating. The maximum hardness of TiN/Al composite coating is 4 times of that of their substrates respectively. The wear resistance of TiN/Al composite coating is 6-8 times of that of their substrates respectively.The study of the wear mechanism of the substrate of Ti6A14V and the laser alloying composite coating shows that abrasive were and adhesive wear occur to the substrate, while micro-ploughing and peeling of TiN reinforcement occur to the composite coating.