The frictional coefficient and wear rate of CDC layer were significantly lowered by chlorine gas treatment at high temperatures due to the formation of a carbon layer. A severe to mild wear transition occurred, depending on the reaction temperature. In this study, the effect of the fraction of transformed carbon layer on the tribological properties has been investigated. The fraction of transformed carbon layer was controlled by varying the reaction temperature of the hydrogen and chlorine gas mixture. The degree of the transformed layer was measured using Energy Dispersive X-ray (EDX) and Raman spectroscopy. The mechanical properties of the partially transformed layer were measured by using a micro-Vickers hardness tester. The variation of the fraction of the transformed carbon was correlated with the tribological and mechanical properties.