Fabrication and Characterization of Ti/TiC Composite Layers by an Electron-Beam Surface Modification

Abstract

In this study, the possibilities for modification and improvement of the surface structure and properties of titanium substrates by a formation of composite Ti/TiC layers are presented. The layers were fabricated by a two-step electron-beam surface modification technique. The first step consists of injection of C powder within the pure Ti substrates by electron-beam alloying technology. The second step is the refinement and homogenization of the microstructure by the electron-beam remelting procedure. During the remelting, the speed of the motion of the samples was varied, and two (most representative) velocities were chosen: 5 and 15 mm/s. Considering both speeds of the motion of the specimens, a composite structure in the form of fine TiC particles distributed within the base titanium matrix was formed. The remelting speed of 5 mm/s led to the formation of a much thicker composite layer, where the TiC particles were significantly more homogeneously distributed. The results obtained for the Vickers microhardness exhibit a significant increase in the value in the mentioned mechanical characteristic in comparison with the base Ti substrate. In the case of the lower speed of the motion of the specimen during the remelting procedure, the microhardness is 510 HV, or about 2.5 times higher than that of the titanium substrate. The application of a higher speed of the specimen motion leads to a decrease in the microhardness in comparison with the case of lower velocity. However, it is still much higher than that of the base Ti material. The mean microhardness of the sample obtained by the remelting speed of motion of 15 mm/s is 360 HV, or it is 1.8 times higher than that of the base material.

Fabrication and Characterization of Titanium Borides by Electron Beam Surface Alloying

“…When alloying elements are introduced into the liquid phase, followed by subsequent solidification, composite layers and coatings are formed with significantly enhanced functional characteristics compared to the initial material [11,12]. A lot of examples exist in the scientific literature aiming to improve the surface properties of Ti substrates employing the electron beam surface alloying technology by forming surface coatings and structures such as Cr [13], Al [14], carbon [15], etc. In all cases, composite Ti-based structures with improved functional properties were obtained, namely titanium aluminides, titanium carbides, etc.…”