Synthesis of TiN/Ti3Al composite coatings on Ti6Al4V alloy by plasma spraying and laser nitriding

The aim of this paper was to develop an in situ method to synthesize the TiN reinforced Ti3Al intermetallic matrix composite (IMC) coatings on Ti6Al4V alloy substrate by using plasma spraying and laser nitriding. The microstructure and mechanical properties of TiN/Ti3Al IMC coatings synthesized at different nitrogen flow rates (NFRs) in laser nitriding were investigated. Results showed that the crack- and pore-free IMC coatings can be made through the proposed method. The morphology of TiN phase and mechanical properties of coatings were strongly dependent on nitrogen NFR in nitriding. The TiN phase exhibited dendrite-like and undeveloped morphology at low nitrogen NFR. At high NFR, the TiN phase showed granular-like morphology. With increasing NFR, the amount of TiN phase in the coating increased, leading to the increment of microhardness and elastic modulus and the decrement of fracture toughness of coating.

► We developed a novel two-step method to synthesize TiN/Ti3Al composite coatings.
► In the first step, pure Al coating was deposited on Ti6Al4V substrate.
► Laser nitriding of Al coating was carried out in the second step.
► Nitrogen flow rate in laser nitriding strongly influenced properties of coatings.