Assessment of the distribution of residual mechanical stresses in plasma coatings

Abstract

Purpose. To improve the performance of plasma coatings by searching for conditions for reducing the residual stresses. To achieve the goal, a method has been developed for determining residual stresses depending on the strength characteristics and the coating thickness.Research methods. Measurements of the mechanical properties of coatings during bending testing. Analysis of the measurement results of coatings strength.Results. A method is proposed for determining residual stresses by using the results of measurements of the mechanical characteristics of a plasma coating. The mechanical characteristics of the chromium-nickel powder coating during bending tests are investigated. A difference in the cohesive strength of the outer and inner layers of the coating was found. To calculate the residual stresses, we used the obtained values of the cohesive strength of the peeled coating and the bearing capacity of the coating adhered to the substrate. It is shown that for coating adhered to the substrate, the bearing capacity is less than the cohesive strength. The assumption that the residual stresses is determined by the difference between the cohesive strength and the bearing capacity of the coating is substantiated. The distribution of residual stresses across the plasma coating thickness and the residual stresses in the zone of contact with the substrate are found.Scientific novelty. It is shown that the cohesive strength exceeds the strength of the coating adhered to the substrate by the amount of residual stress. The distribution of residual stress and bearing capacity from changing coating thickness is found.Practical value. The results of measurements of cohesive strength and residual voltage make it possible to justify the reliability of the use of plasma coatings and analyze the data of strength measurements in order to determine the performance of parts.