Metrological aspect of oxide coatings growth on products with an aluminum substrate
The article presents the study results of the influence of process mode parameters on the thickness of the oxide coating of aluminum-based products. Ceramic-like coatings were formed by the microarc oxidation method on AD31 alloy using a capacitor process installation with a sinusoidal current at a constant current density of 15 A/dm2 in the anodic-cathode mode. The study of oxide film growth was performed using a B7−517 thickness gauge. It is shown that for approximating the dependence of the oxide film thickness on the processing time of products, it is advisable to use piecewise approximation by mathematical functions of different types: exponential and linear. The use of such an approach is due to the influence of diffusion and chemical processes that dominate at the stages of spark and microarc discharges of the microarc oxidation process. However, this approach is not applicable for the purpose of analyzing the dependence of the film thickness on the concentration of sodium hydroxide and the ratio of the anodic and cathodic current components. In this case, the approximation is made by a quadratic function, due to the influence of nonlinear factors-impacts of the technological process. The results of the metrological analysis confirmed that the error in the adequacy of these models does not exceed 5%. It is advisable to use the obtained results when producing coatings with the required functional characteristics by the microarc oxidation method.