On the Possibilities of Increasing the Diffusion Resistance of Protective Silicide Coatings on the Surface of E110 Alloy

The study is devoted to searching for possibilities to improve the thermal stability of protective silicide coatings on zirconium alloys by reducing the intensity of their diffusion interaction with the base material. The possibilities of forming barrier layers both from molybdenum silicides with a reduced silicon content and from tungsten are experimentally evaluated. The structural and phase state of diffusion pairs subjected to vacuum annealing at temperatures of 1100–1450°C for 3–9 hours are studied by scanning electron microscopy and X-ray spectral microanalysis. It is determined that a 1-μm-thick tungsten barrier layer reduces the degree of diffusion interaction between molybdenum silicides and a zirconium-based alloy. However, in the interaction region, a porous and brittle layer is formed, leading to peeling of the coating. A decrease in the average silicon content in molybdenum silicides can also significantly reduce the degree of their interaction with zirconium alloys, but does not lead to loss of coating adhesion. The features of the microstructure and chemical composition formed as a result of the diffusion interaction of phases are revealed. The effective kinetic parameters of the processes of diffusion interaction and their temperature dependence are determined.