Влияние дополнительной термической обработки газофазных неоднородных поверхностных слоев на остаточные напряжения и адгезионную прочность стали

The article presents the results of a study of the surface layers obtained by the deposition of organometallic chromium compounds on the base metal, and the structural changes occurring in them when exposed to additional heat treatment in the form of subsequent annealing. It is noted that the type of coating and its structure primarily depend on the deposition temperature; therefore, there are three main types - kinetic, transitional and diffusional. Each such type of surface layer is determined by its own mechanism of formation, and as the temperature changes, one transforms into another. The metastable state of such surfaces, which are supersaturated solid solutions, upon additional heat treatment leads to significant structural changes and the formation of a nanostructured composite layer. The possibility of obtaining nano-modified layers by forming the structure of a matrix solution with dispersed-dissolved secondary nano-sized particles of chromium carbides is shown. The modes at which crystallization of the amorphous phase begins with the release of nano-sized particles of chromium and chromium carbides have been determined. The modes with the maximum and minimum levels of residual stresses, which directly affect the performance of products, have been established, and the effect of additional annealing on the distribution of residual stresses has been studied. It is shown that the process of crystallization of the amorphous phase during annealing and the parallel process of coagulation of carbides causes the appearance and growth of residual stresses. The influence of residual stresses on the adhesion strength of surface layers, which largely depends on the main parameters of heat treatment - temperature and time, has been investigated. Comparison of adhesion strength before and after annealing showed that the overall level of adhesion strength during heat treatment of coatings decreases insignificantly, by 7-10%.