大気中での高周波誘導加熱による Ti-6Al-4V 合金の高速酸窒化処理

In this study, a rapid oxynitriding technique based on induction heating was developed for the titanium alloy Ti-6Al-4V, and its effects on surface characteristics of the alloy were investigated. The surface microstructures of the alloy were characterized by employing a scanning electron microscope, electron back-scatter diffraction, X-ray diffraction and nano-indentation tests. Induction-heating in air for 60 s caused the formation of a hardened layer on the Ti-6Al-4V alloy surface, which can be attributed to the diffusion of oxygen and nitrogen atoms. When water quenching was performed after heating, transformation to an acicular martensitic α’ phase occurred, resulting in increased in substrate hardness. However, cracks were initiated at the surface of the oxynitrided alloy. The cracks were eliminated through fine particle bombarding treatment, whereas the hardened layer formed by the oxynitriding treatment remained. The obtained results thus indicate that the oxynitriding technique developed in this study can enhance the wear resistance and tensile strength of the Ti-6Al-4V alloy within a short period of time.