The Study On Quantitative Measurement Test Of Thermal Spray Coating Residual Stress

In recent years, with new technology and new materials be developed and applied. The thermal spray technology play some roles in corrosion resist, wear resist, high temperature resist, in more and more areas, have greatly increased the life expectancy of parts. But it's inevitable that there are residual stresses in the thermal spraying coatings, and then the residual stresses will take great influence to the performance of the products. A lot of failures, such as cracking, delamination and buckling, can be induced by the excessive residual stresses in the coatings. Therefore it's positively significant that studying quantitatively the residual stresses in the thermal spraying coatings.In this dissertation, FeCrBSi coatings were separately deposited by supersonic plasma spraying, high velocity oxy fuel spraying and plasma spraying. The microstructure, porosity and mechanical properties of coatings were experimentally determined and analyzed by Scanning Electron Microscopy (SEM), X-Ray Diffractometer (XRD) and nano-indention tester. After relaxation of residual stresses of the thermal spraying coating by cutting, the residual stresses within the cutting side was measured by Moiréinterferometry method, and the distribution along the coating thickness was gained. The residual stresses on the coating surface were measured by the X-ray residual stress measurement system in order to make a comparison. The stress constant was induced by theory calculation. The residual stresses of the equal interval distance within the coating surface were measured by 4-points method. In addition, the effect of annealing treatment at different temperatures and different time on microstructure and mechanical properties of supersonic plasma sprayed FeCrBSi coatings were studied.The results indicated that the coating deposited by supersonic plasma spraying has a better combination property than the other two kind coatings. Residual stresses meared by Moiréinterferometry method in the three kind of thermal sprayed coatings were tensile, the maximum value were on the surface and decreased as the distance to coating surface increasing, then suddenly changed near the interface between the coating and the substrate. The results meared by X-ray diffraction method showed that the changes are not obvious and the average result was near the value by moiréinterferometry method. Proper annealing treatment can decrease porosity, increase elastic modulus and microhardness and release the residual tensile stress of the coatings. However, when the annealing treatment temperature above 600℃or the holding time above 2h, the quality of the coatings fall down.The theoretical research and practicable of this dissertation demonstrated that the application of Moiréinterferometry method in mearing residual stress of coatings is available and has broad prospects for future development, and proper annealing treatment can improve the combination property of coatings.