Aspects of Structure Formation in Surface Layers of Steel after Laser Alloying from Various Coatings

The present research reports the results of the experimental studies on the structure and properties of steel surface layers subjected to laser alloying from various composition coatings created by the slip method, electric spark alloying, and ion-plasma spraying. It is demonstrated that laser treatment of coatings increases the alloyed layer depth, purposefully changes the structural state and presets the necessary operational properties of the surface layers of the products. This ensures a smooth transition of properties from the coating to the steel backplate and a decrease in the stress localization at the interface of the “coating-backplate” composition. The reason is the diffusion processes during the coating mixing with the surface layer of the steel backplate melted by laser radiation. It was found that the possible violation of the irradiated surface microgeometry of the coatings must be corrected to select the spot overlap coefficient in the range of 0.7–0.8.

It was established that the chemical composition rational choice and the method of coatings application to the metal products surface of various functional purposes under temperature-force exposure during laser irradiation contributes to an increase in hardness of the irradiated working zones by 30%–50%, wear resistance by 2–3 times compared to volume hardened steel. The problem of improving properties, preventing cracking and grain growth in the composition of “coating — transition zone — steel backplate” while retaining core metal properties is solved by using the established modes of pulsed laser surface fusing of hardening phases from coatings, which account for 30%–50% of the irradiated zone volume.