Research on the Technology、Structure and Performance of the Coating by Plasma Spraying

Plasma spraying is a important surface treatment technology, The coating can enhance and restore the surface of materials . At the same time, material surface will get particular properties, so plasma spraying technology is widely used.The preparation technology of Ni6A, WC-Co and Al2O3+13%TiO2 coatings on 45 steel by plasma spraying is studied in this paper, and the coating’s porosity, microhardness and bond strength have also been tested. The phase structure and morphology of coatings are investigated by XRD and SEM, the wear property of coatings are compared with Crl2MoV steel. Moreover, the thermal stress of coatings are calculated by Ansys software, and compared with the gradient coating. It offers the theory support for the design and preparation of coatings in the future. By analysis and study, the results indicate:The coatings have typical layer structure, porosities in them, and mechanical bond with the substrate. M60A have minimum porosity rate, and maximum bond strength. WC-Co have maximum microhardness. Spraying grain have complicated transform of structure in spraying process, it leads to an important effects on the properties of coatings.In the case of lubrication, the wear-resistance of coatings are better than Crl2MoV,and that of WC-Co is the best. Ni60A mainly is abrasive wear, with fatigue wear. The major wear mechanism of AT13 and WC-Co are slight abrasive wear and adhesion wear. In the case of fixed abrasive, the wear-resistance of AT 13 and WC-Co are better than Crl2MoV, and M60A is a little worse than Crl2MoV. Cr12MoV and Ni60A are abrasive wear by ploughing. AT 13 and WC-Co are locally scaled off.The stress of coatings have a large break near the interface, the maximum stress of WC-Co and Ni60A are near the interface of coatings and substrate, that of AT 13 is near the interface of the coating and bonding layer. The axial pulling stress exist in WC-Co and AT 13 coatings, and the axial pressing stress in Ni60A coating. The gradient coating can decrease the damage of the residual thermal stress.