Effects of pretreatment on borocarburized of TC4 titanium alloy

The effects of surface carburization pretreatment on borocarburized of TC4 were investigated. A carburized layer was fabricated on the surface of the TC4 by a solid carburizing method. Then the carburized sample was subjected to solid borocarburizing. The surface morphologies, microstructure and phase constituent of the borocarburized samples were analysed by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The results demonstrate that after the pretreatment and borocarburized, the diffusion layer consists of TiB₂, TiB and TiC phases, whose total thickness is about 35 μm. And the hardness of the exterior surface is 3000 HV, which is about 9 times of the TC4 substrates. Meanwhile, the pretreatment could significantly decrease the friction coefficient and improve wear resistance of the borocarburized sample. (paper)