Microstructure and tribological properties of in situ synthesized TiN/Ti3Al intermetallic matrix composite coatings on titanium by laser cladding and laser nitriding

TiN reinforced Ti3Al intermetallic matrix composite (TiN/Ti3Al 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/Ti3Al IMC coatings were granular-like, flake-like, and undeveloped dendrites at lower N2 flow rate; and granular-like, undeveloped and developed dendrites at higher N2 flow rate. In addition, the volume fraction of the TiN phase increased with increasing nitrogen flow rate. The hardness of the TiN/Ti3Al IMC coatings was higher than that of the Ti3Al coating, which increased with increasing volume fraction of the TiN phase. Friction and wear tests revealed that the wear resistance of TiN/Ti3Al IMC coatings was superior to those of pure Ti and Ti3Al coating. It is well worth noting that the TiN/Ti3Al IMC coatings showed excellent wear resistance under lower normal loads.