Features of Gradient Structure Formation on the Surface of VT1-0 Titanium after Combined Treatment

Abstract

This article examines the development of concepts related to gradient layers and various methods for their formation to enhance and protect metal surfaces from adverse environmental conditions. The study focuses on commercially pure titanium (VT1-0) subjected to electro-explosive alloying and various types of combined processing. Light microscopy of straight and oblique cross-sections revealed that, in gradient layers, structural transformations occur progressively with increasing depth from the surface. These transformations affect not only the microstructure but also the concentration of impurities, alloying elements, and the degree of completeness of these changes. Cell, grain, and subgrain sizes, as well as defect density and substructure, also evolve in the same direction. Electro-explosive carburization increases surface microhardness to 800 HV. Subsequent electron beam processing further enhances microhardness, reaching 2500–3000 HV. This treatment also results in the formation of two microhardness maxima at depths of 20 and 70–80 µm, while extending the hardened zone depth from 50 to 90–100 µm. Electro-explosive carboboriding raises surface microhardness to 2500–3000 HV, with the hardened surface layer reaching a thickness of 120 µm. Carburization of titanium produces a discontinuous coating on the surface.