Thermophysical parameters of the process to obtain the required microgeometry of composite electroplating coatings based on chromium

Abstract

Reviewed the thermal aspects of the process galvanotecniks deposition (GTD) chromium coatings. A mathematical model is proposed to predict the stress–strain state of the composite coating formed depending on the created temperature field over the entire thickness of the restored part. With this consideration of the chrome plating process, the main feature is a very short time of action of the heat source of high power. The temperature gradient in this case reaches the value of about 100 °C/s. The proposed method of calculation allows to determine the temperature-speed grinding cycle as a function of the surface layer temperature, temperature gradient and various technological conditions. In the real process, it is necessary to take into account both the penetration directly into the contact zone of the tool with the part in small amounts of cold liquid, and its properties that undergo significant changes due to the such a sharp heating. These circumstances of the real process force to complicate mathematical calculations. The presence of heat exchange at the boundary with the environment affects the reduction to the total heat content of the surface layer. However, the maximum heating temperature have varied very slightly. Therefore, when calculating the maximum temperature directly below the source, the heat exchange was neglected in the model and the surfaces of the contacting parts were considered adiabatic. In the course of the study, a mathematical model of the temperature heating to restored part was calculated. This made it possible to determine the analytical dependence of the temperature gradient over the thickness of the applied layer. During the determining of the parameters from the galvanic process, presented model allows to take into account the residual temperature stresses formed in the preparation of composite coatings. However, to identify all theoretically possible, but not technological point of view, the modes of deposition of the coating in the framework of the existing models is not possible. This is so, because the system of equations can be solved only by numerical methods.