高硬度鋼の高速切削加工におけるTiSiN被覆切削工具の摩耗メカニズム

概要

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TiSiN coatings are widely used for cutting tools due to their higher hardness and higher oxidation resistance. This study aimd to clarify the wear phenomena of a TiSiN coated cemented carbide end-mill in higher cutting speed of hardened die steels. The coating structure was the combination of TiSiN coating as top layer and TiAlN coating as under layer. The wear phenomena of the end-mill were studied by cross-sectional TEM observations on the cutting edge. Both wear and deformation of the cutting edge progressed simultaneously. The top layer of TiSiN coating was effective to restrain both the propagation of cracks and deformation and improved the wear resistance of the cutting tool. In the layer of TiAlN, it was evident that the crack took place perpendicularly to the surface of the cemented carbide matrix and progressed, resulting in the deformation due to the change in direction of the columnar structure in the layer. The diffusion of Co in the substrate into the TiAlN layer through the crack caused to promote the deformation of the layer.