Microstructure and tribological properties of in situ synthesized TiN/Ti_3Al intermetallic matrix composite coatings on titanium by laser cladding and laser nitriding

摘要

TiN reinforced Ti_3Al intermetallic matrix composite (TiN/Ti_3Al IMC) coatings were in situ synthesized on a pure Ti substrate with Ti + Al mixed powders in nitrogen atmosphere by laser cladding and laser nitriding. It was found that the growth morphologies of the TiN reinforced phase in the TiN/Ti_3Al IMC coatings were granular-like, flake-like, and undeveloped dendrites at lower N_2 flow rate; and granular-like, undeveloped and developed dendrites at higher N_2 flow rate. In addition, the volume fraction of the TiN phase increased with increasing nitrogen flow rate. The hardness of the TiN/Ti_3 Al IMC coatings was higher than that of the Ti_3Al coating, which increased with increasing volume fraction of the TiN phase. Friction and wear tests revealed that the wear resistance of TiN/Ti_3 Al IMC coatings was superior to those of pure Ti and Ti_3 Al coating. It is well worth noting that the TiN/Ti_3 Al IMC coatings showed excellent wear resistance under lower normal loads.