Study On The Influence Factors Of Residual Stress In Spraying Coatings

With the development of science and technology, the surface protection work of the mechanical mechanism is getting more attention. Thermal sprayed coating, a kind of surface protection technology, has been used much more than ever. However, they can be rupturing, warping, stripping or other failure during the service of the thermal sprayed coatings. It has been found that the reason of the failure on thermal sprayed coatings is mostly of the residual stress in coatings & substrate system in many studies. So the study on the influence factors of residual stress may play a guiding role in the work of coatings protection. The study of influence factors on residual stress in thermal sprayed coatings is of great significance.In this paper, the measurement of residual stress of thermal sprayed coatings is blind hole method which is economic and mature. The measurement test is divided in two parts: the one is measuring the distribution of residual stress in NiCrFeMo-GH4169 of the same thickness and investigating the distribution of residual stress beside the edge of coatings; the other one is measuring and investigating residual stress in three systems, Ni CrFeMo-GH4169, NiCrAlY-GH4169 and NiCrAlY-TC4, in the same location of three different thickness. This article also has simulated the residual stress coming from the heat conduction in the process of thermal spraying by meanings of finite element on ANSYS to verify and refine the test rule.Through experimental analysis, the coating edge effect has been found, which is the decreasing of normal stress and the concentration of shear stress on the edge of the coatings, and with the increase of the thickness of the coatings, residual stress is changing from the compressive stress to tensile stress. Through the finite element simulation analysis, it has been found: the change of normal stress is smooth, the stress value is high, the change of the shear stress is smooth, and the stress value of shear stress is almost 0, in the center of the coating; beside the edge of the coatings, normal stress is decreasing sharply, shear stress is increasing first and then decreasing sharply; with the increasing of coating thickness, the change of the normal stress is the tendency of tensile stress' increasing, shear stress' decreasing, on the edge of the coating. Therefore, the result of finite element analysis can refine the accuracy of the distribution from the laboratory findings.