tool wear in hard machining

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The tool wear in hard turning is influenced by various parameters such as cutting conditions, workpiece hardness, tool material and interaction of tool-workpiece and so on. Generally, the cutting tool performance is limited by flank wear, nose wear, crater wear, edge chippings, or combination of these. The tool wear either occurs gradually by adhesive or abrasive wear, through plastic deformation, through discrete fracture mechanism, or by combination of these. The occurrence of each wear mechanism depends on high thermal, mechanical and chemical loads generated in hard machining. Carbide cutting tools are the regular tools for machining of alloy steels and cast iron. These cutting tools have a high degree of toughness but poor hardness compared to advanced tool materials such as cermet’s, ceramics and PCBN. In order to improve the hardness and surface conditions, carbide tools are coated with hard coatings such as TiN, Ti(C,N), (Ti,Al)N, (Zr,C)N, Al2O3 and so on. While machining, observed that multilayer coated (TiN/TiCN/Al2O3/TiN) carbide tool performed better and longer tool life than un-coated carbide tool.

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