Abstract
To evaluate the influence of hybrid surface modification processing on the rolling contact fatigue life, we used a roller pitting test comprising a combination of high strengthening by Super Rapid Induction heating and Quenching (SRIQ) and improvement of the tribological quality by a Diamond Like Carbon (DLC) membrane. The applicability of the process to a small gear was examined. Results show that the rolling contact fatigue life of the SRIQ+DLC specimen was longer than that of SRIQ specimen at all loads. Subsequent SEM observation of fractures showed that many micro-surface cracks and pittings along with pitting caused fracturing of the SRIQ specimen. However, the SRIQ+DLC specimen showed few micro-surface cracks aside from the pitting causing fracture. Many internal cracks were found. Based on these results, we infer that improvement of the rolling contact fatigue life is introduced by retarding of the generation of surface damage attributable to the decrease of tangential stress brought by superior low friction and excellent wear resistance of the DLC membrane. Therefore, SRIQ+DLC compound surface modification, which improves tribological and fatigue properties, is suggested as effective for improving rolling contact fatigue life. Regarding SRIQ, it is possible also for the discharge of carbon dioxide to produce a substantial decrease in comparison to other heat treatment processes. It can contribute also to protection of the terrestrial environment. It might be said that a new hybrid surface modification process has been produced.
