| With the miniaturization of parts, friction has more obvious effect on the microforming process than that in macroforming. For the existing of friction size effect, liquid lubrication is not suitable for the microforming. More attentions have been paid to DLC coating for its superior tribological characteristics. In this investigation, several dies with micro-channel of different width from 0.6 mm to 1.4 mm were developed. Plasma source ion implantation (PSII) was selected to deposit DLC coating at the inner surface of micro channel dies, and analysis of micro-channel dimension effect was carried out by measuring the properties of DLC coating inside of micro-channels. The surface topography of DLC coating shows that the DLC coating exhibits an obvious island growth. With decreasing of micro-channel width and increasing of distance from upper surface, the nanohardness becomes small. This indicates that the mechanical properties become poor. Scratch tests show that the failure mode is brittle fracture for high contact pressure. With the decreasing of channel width, the DLC coating is not easily peeled off even when DLC coating is broken for the large plastic deformation of substrate. The ratio of sp3 and sp2 bonds is changed by the channel width and distance from upper surface. The fraction of sp3 bond in DLC coating becomes smaller. The results shown above indicate the mechanical properties of DLC coating becomes poor with decreasing of channel width, and the adhesion strength is improved. |
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