Investigation On The Reactive Plasma Sprayed Titanium Nitride Coatings

In this paper, TiN coatings was formed by means of gas tunnel reactive plasma spray torch.And gas tunel reactive chamber was modified. The parameters of reactive plasma spraying TiN coatings have optimized, the mechanical and tribological and corrosion resistant properties of the coatings were investigated, and the formation mechanism was discussed.During the optimizing reactive plasma spraying TiN coatings, it was found that coatings in which TiN phase acts as main phase could be fabricated within the scope of wide plasma power. The microstructure and microhardness of TiN coatings are much better when plasma power being about 36kW. The microstructure and microhardness raised when N₂' flux raise form 1. 5m³/h to 2. 5m³/hExperimental results show that reactive plasma spraying TiN coatings mainly contained TiN which is the main phase. The cross-sectional micro-hardness of the TiN coatings could be maximized to HV2121.2. It proved that the toughness was improved by observing the micro-hardness impree in cross-section surface and caculating the fracture toughness.The wear-resistance of reactive plasma spraying TiN coatings is higher than Al₂O₃ coatings under the unlubricated condition.The mechanism of wear under low loads is light Brittle spalling wear. Under heavy loads it is fatigue wear.In DC corrosion experiments,the coatings covered substrates' resistance to neutral and acid solution is 4 times to the bare substrate.The coatings protected the substrate by preventing the solution away from it.The TiN formation is mainly combustion synthesis with molten Ti in the N₂ gas in the process of reactive plasma spraying TiN coatings. Combustion mechanism is that reaction can be proceeded by reaction formation of TiN product between Ti and N₂.