Shogo Takesue 1, Shoichi Kikuchi 2, Hiroyuki Akebono 3, Jun Komotori 4, Kengo Fukazawa 5 and Yoshitaka Misaka 5
1 School of Integrated Design Engineering, Graduate School of Science and Technology, Keio University
In this study, the effects of gas blow velocity on the surface properties of a Ti-6Al-4V alloy treated by a gas blow induction heating (IH) nitriding system were investigated. The surface microstructure of the treated specimens was characterized using scanning electron microscope and X-ray diffraction. In addition, micro-Vickers hardness and nanohardness were measured and reciprocating wear tests were conducted to evaluate the modified surface layers. 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 transformation to an acicular α phase, which involves apparent grain coarsening.
surface modification, nitriding, titanium alloy, induction heating, gas blow velocity, microstructure
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