Determination of the influence of variation in the number of layers in multilayer coatings on the inhibition of hydrogenation processes and thermal barrier characteristics

Abstract

The evaluation results of the application of multilayer AlN–TiO₂ coatings as protective thermal barriers and anticorrosive coatings that protect metal structures from corrosion processes during hydrogenation are presented. During the studies conducted, it was determined that increasing the number of layers in the coatings while maintaining the overall thickness allows for an increase in resistance to external mechanical effects (pressure and friction). This is because of the presence of interlayer boundaries that prevent the propagation of microcracks under external loads. At the same time, increasing the number of layers from 10× to 20× results in a slight decrease in adhesive strength due to a reduction in the adhesion of the layers with small thicknesses (approximately 50 nm). Simultaneously, the presence of a large number of layers inhibits hydrogen diffusion mechanisms in the coatings, which is expressed not only as an increase in resistance to cracking during indentation of coating samples after hydrogenation but also as less pronounced morphological changes in the topography of the coating surface associated with the formation of hillock-like gas-filled inclusions on the surface. An analysis of the thermal insulation characteristics of the coatings revealed that an increase in the number of layers leads to an increase in the temperature difference between the front and back sides, indicating an increase in thermal insulation due to the presence of interlayer boundaries, which leads to a slowdown in heat transfer.