チタン合金の耐摩耗性を改善する手法としては, 窒化が最も一般的であるが, 長時間要することや加熱により素材の強度が低下することなどが問題視されている。本申請では, 数分オーダーの超短時間処理により, チタンの耐摩耗性を改善する手法の構築にチャレンジした。その結果, 高周波誘導により基材を加熱した状態で窒素ガスをブローすることにより, わずか3分の処理で, 数時間のガス窒化より深い効果層を得ることに成功した。
The effects of gas blow velocity on the surface properties of a Ti-6Al-4V alloy treated by gas blow IH nitriding were studied. The surface microstructure of the treated specimens was characterized using SEM and XRD. Vickers hardness and nanohardness were measured and reciprocating wear tests were carried out. The results showed that the nitriding of a specimen was facilitated by using a smaller gas blow nozzle. Incorporating the smaller nozzle resulted in an increase in gas blow velocity, which in turn increased the IH power and the temperature inside a specimen, thus accelerating the nitrogen diffusion. Moreover, nitriding at a lower treatment temperature (973 K) was achieved by increasing gas blow velocity. The specimen nitrided at a lower temperature with a high gas blow velocity exhibited better wear resistance than the untreated specimen. This process also inhibited trans-formation to an acicular phase, which involves apparent grain coarsening.

研究種目 : 挑戦的萌芽研究
研究期間 : 2016～2017
課題番号 : 16K14121
研究分野 : 材料工学