The Research On Spreading And Crystallization Behavior Of TiCN Coatings Prepared By Reactive Plasma Spraying

In this paper,the spreading and crystallization behavior of the coatings were studied by numerical simulation and experimental analysis.The heat transfer of nickel droplets in plasma spraying was investigated by computational fluid dynamics(CFD)method,which provided theoretical support for the study of crystallization behavior of TiCN coatings.By studying the influence of different factors on the crystalline state of TiCN coatings,the process conditions for preparing TiCN coatings by reactive plasma spraying were further optimized.The calculation model of single droplet spreading was established,and the effect of substrate material on droplet spreading heat transfer was studied.The results show that the substrate material has no effect on the heat transfer of the droplets for a short time before and after the droplets impact on the matrix.With the process of droplet spreading,the distance of heat transfer in vertical direction increases with the increase of thermal conductivity,and the temperature drops fastest at the impact point.The rapid crystallization of the nucleus reduces the actual spreading diameter of the particles.The effects of droplet impact temperature and velocity on spreading were studied by simulating the spreading of droplets impacting the matrix under different conditions.Within a certain temperature range,with the increase of droplet temperature,the heat transfer from droplet to matrix increases during the spreading process,which results in the relative increase of matrix temperature.When the melting point of matrix is reached,the melting of matrix will affect the spreading of droplets.With the increase of droplet impact velocity,the distance of heat transfer along the direction of the substrate surface increases,and the effective contact area of particle spreading increases.Comparing the spreading rule of TiCN and nickel droplets on different substrates,combining with the analysis of the crystal morphology at the interface of TiCN coating and substrate,the spreading diameter rule of TiCN particles and the growth pattern of columnar and dendrite in the coating are basically in accordance with the heat transfer rule.The effects of different elements on the crystallization behavior of TiCN coatings were studied.The results show that the position of the interface between TiCN coating and matrix is smaller than that of the coating surface,and the increase of carbon content leads to the coarsening of grains,the chances of heat dissipation parallel to the substrate direction increase,and the number of dendrites increases.With the increase of Cr and Cu content,the grain refinement in TiCN coating is obvious.For TiCN coating containing Ni,the heat treatment process at different temperatures will not be changed.Variable crystalline morphology of TiCN composite coating.XRD results show that the addition of Cu does not change the main phase material Ti C0.7N0.3 of TiCN coating.There are Ti-C,Ti-N,Ti-O,C-N,N-O,Cu-O bonds in the coating.The existence of Ti N0.3O phase and Cu2O phase is confirmed by EPMA analysis.The existence of copper and its influence on the crystallization process of TiCN are confirmed by EPMA analysis.The test results of properties of Cu/TiCN coatings show that the grain size of TiCN coatings can be refined by Cu,and the crack propagation energy of the coatings can reach45.8 J/m~2,which increases the toughness of the coatings,but it has no positive effect on the hardness and wear resistance of the coatings.