Effects of Deflection Scanning of Electron Beam on Microstructure, Hardness and Treated Depth of TC18 Titanium Alloy

The high frequency deflection scanning of vacuum electron beam technology (DSEB) with line by line scanning mode and no overlap was employed to treat the surface of TC18 titanium alloy, for obtaining a homogeneous hardened surface layer. The purpose of the present work was to investigate the effects of critical process parameters, including beam current, focus current and treatment times, on the microstructure, hardness and treated depth of the treatment area. The treated specimens were characterized by SEM, optical microscope, and Vickers hardness tester. After treated by DSEB, the hardened surface layer is formed, which is mainly consisted of the acicular martensite, and the surface hardness of the treatment area is improved. Moreover, the microstructure of the hardened zone is homogeneous and has no obvious transition at the contact parts of two adjacent electron beams scanning. The depth of the hardened zone can be more than 200 μm and basically constant. These results show that DSEB is a very promising technological solution for the surface heat treatment of titanium alloy of large area and complex components.