Microstructure of alloyed layer and nitriding process in foreign metals under arc sprayed Ti composite coating

We investigated the nitriding process and the microstructure of the alloyed layer between foreign metals under composite arc spraying using two different wire materials, Ti and the paired metal (Mo, Ni, Cu and Al). The Ti element in the composite coatings (Ti-Mo, Ti-Ni, Ti-Cu and Ti-Al) was of TiN and/or TiN_0.3, and the oxide or nitride of the paired metal was not found in the coatings. An intermetallic compound (Ti₂Al) in the Ti-Al coating was detected in the XRD pattern, but none was detected in the other coatings. It is considered that the reaction of Ti with foreign metal occurs only in the solidification process at the moment of droplet impact. The composite coatings were of very dense packing, and had the diffusion layer in the interface region between the foreign metals. The solute element, Ti in the composite coating Ti-Mo, reacted with nitrogen to form many micrograins of TiN_0.3 within molten Mo during thermal spraying. In the other coatings (Ti-Ni, To-Cu and Ti-Al), eutectics were mainly identified, and the Ti nitride in the alloyed layer between foreign metals was only TiN_0.3. In addition, the intermetallic compounds, which were not detected in the XRD pattern, were identified in the TEM observation.