Study On The Nanostructure TiCN Coating By Reactive Plasma Spraying Process

In this study, the nanostructured TiCN coating was prepared by reactive plasma spraying process, meanwhile, the carbon source and spraying process parameters were optimized, the constituent phase, microstructure and grain size of the coatings were analyzed through various characterization techniques of XRD, SEM, XPS and TEM, and the mechanical property was evaluated as well. The contents and results of this study are mainly as follows:The feeds were prepared by graphite and carbon black as carbon source using spray Granulation method and studied by the thermo gravimetry and differential scanning calorimeter(TG-DSC). The results show that the reactive temperature between graphite and titanium is 1524.7 oC, which is lower than that of carbon black. Additionally, the coating prepared using graphite as carbon source has higher carbon content and the ratio of C vs N is 7:3.The influence of the particle size of the graphite was also explored. The constituent phase of the coatings changes from TiC0.2N0.8 to TiC0.7N0.3 with the decreasing of the particle size of graphite. The higher density of the coating could be obtained by using small size graphite. The coating prepared by particles size of 5 μm graphite exhibits superior microhardness, reaching at 1399 HV0.2, which was analyzed using the method of Weibull.The spraying parameters were optimized through orthogonal experiment, and the results show that the electricity is 500 A, the flux of N2 is 60 L/min, the spraying distance is 100 mm.What can be obtained through the microstructure is that layers of the coating are bonded very well to each other. The main phase of the coating is TiC0.7N0.3, especially, having strongly preferred orientation in(111) and(200) crystal plane. The composition of the coating was also determined by XPS, which proved the existence of the free graphite and CN in the coating; The TEM images show that the TiCN coating is nanocrystalline and the crystal size ranges from 60 nm to 100 nm. Besides, some amorphous phase was also discovered in the coating.TiCN coating exhibits superior microhardness(1674 HV0.1), binding strength(26.7 MPa), and excellent wear-resistance. During the wear test, the wear mechanism changed from micro-cutting, plough to fracture wear with the load increased. In addition, the line scanning analysis shows that the adhesive wear and the oxidation occurred during the wear test due to the effect of the friction heat.