Because of the poor effect of lubricant in microscale dimensions, tribological issues in microforming are encountering further severe problems in the enhancement of performance in microforming operation. Therefore, as an approach to enhancing the tribological performance of the microdie surface, in the present study, we applied surface texturing on the microdie with the expectation of the wear-debris-ejecting effect. A microtextured surface was realized by using metallic masks during the deposition of diamond-like carbon (DLC). To characterize the basic tribological property of textured DLC film, the ball-on-disk tribology test was carried out. Furthermore, a system for in-situ observation during microbending was developed to characterize the practical applicability of surface texturing in the microforming operation. The textured DLC film showed a lower coefficient of friction than that of the nontextured DLC surface. Additionally, we demonstrated that surface texturing promoted the wear-debris-ejecting effect during the microforming operation.
Abstract. Application of diamond like carbon (DLC) films are reported in several microforming processes, in view of its great tribological performance owe to the low friction and the high chemical stability. However, due to its high internal residual stress, the film properties with the low adhesion strength and the high wear rate under severe tribological conditions are still remain as technical issues. However, since the dynamic variation of the contact state cannot be observed during the forming operation, it is difficult to recognize the origin and the influential tribological factors of tool life for DLC coated microforming die. Therefore, the appropriate DLC film properties for the contact state in microforming operation have not been clarified. To observe the dynamic variation of the contact state during the microforming operation, present study developed a novel microforming die assembly installed the in-situ observation system with silica glass die and high speed recording camera. By using this system, the dynamic delamination behaviour of DLC films during the progressive micro-bending process was successfully demonstrated. The influential factors for the durability of DLC coated microdies were discussed.
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