積層構造を有するDLC層を被覆したステンレス鋼の疲労特性

This study was conducted to investigate effect of DLC (diamond-like carbon) multi-layer coating on fatigue properties of stainless steel SUS304. The DLC multi-layer of 2.2 μm thickness possessed a laminated structure composed of very thin DLC layers in which hardness was different. This structure was selected to prevent loss of the functionalities of the DLC layer through fracture or peeling which could occur under impact force. The DLC multi-layer was generated by UBMS(unbalanced magnetron sputtering) method. The result showed that microstructure of the substrate was unchanged by the DLC multi-layer coating conducted at relatively low temperature, so that the mechanical properties was maintained to the same level of the untreated material. The fatigue strength was improved by the DLC multi-layer coating since the layer having a high strength sufficiently adhered to the substrate and prevented initiation of fatigue cracks from the surface. However, its fatigue strength was slightly lower than that of the material coated by DLC single-layer. Such difference in the fatigue strength between the materials coated by the DLC multi-layer and single-layer would result from the difference in the fracture strength of the layers.