순수 타이타늄의 표면경화 특성에 미치는 열화학처리 유지시간의 영향

Commercially pure (CP) titanium shows low wear resistance and scratch resistance in spite of high specific strength and toughness. In order to improve these problems, the effect of holding time on surface hardening of CP titanium by thermo-chemical treatment (TCT) process was investigated. The surface hardening processes were conducted as a function of treatment holding time for 0.5 hr, 1hr and 2 hrs under nitrogen gas atmosphere at 800 ℃ (thermo-chemical nitriding temperature). The hardness of TCTtreated CP titanium was increased more than the as-received CP titanium by 3 to 4 times, which this layer had continuously gradient hardness distribution from surface to substrate. As the holding time was increased, the whole hardened layer also be came thicker and the depth of Ti2N+TiNx layer was higher. Ball-on-disk tests showed that wear resistance of the samples was improved significantly compared to CP titanium. From these results, the TCT process has proven to be an attractive inner-layered surface hardening process by reducing unnecessary process. †(Received December 9, 2013)