COMPARE MACHINABILITY OF SINTERED COMPONENTS BY USING DIAMOND-LIKE CARBON (DLC) COATING CUTTING TOOL

摘要

The powder metallurgy (P/M) technique is known for its capability of producing net-or near-net-shape parts. Its specific characteristics have resulted in low cost and eliminating secondary machining. However, more and more P/M (powder metallurgy) components do require additional operations to fulfil their complex geometry features and surface roughness specification. Many of the machining factors that influence the machinability of cast and wrought parts, such as cutting speed, feedrate, tool geometry and shape, are also considered in the machining of P/M parts. However, composition, structure, and porosity of P/M are additional factors to be considered. Porosity in the P/M structure can decrease the machinability and shorten the tool life. Different variables have been considered in the material composition. P/M densities and free machining additives, such as manganese sulphide (MnS), have been regarded as the two main factors of material composition which dominates the machining performance. Diamond-like carbon (DLC) coating has been applied to the cutting tool to enhance its strength and wear resistance. By using the plasma assisted chemical vapour deposition (PACVD), the carbon film can de deposited on the cutting tool surface. This paper will compare the machinability of sintered components by using DLC coated cutting tool. The machine parameters in this single point turning operation include P/M component densities, free machining additive, cutting speeds and feedrates. Comparisons of machinability in this research are mainly based on the surface finish, roundness and chip formation. Furthermore, observations are made on how the porosity of P/M structure and machining parameters affects the machinability of sintered components when using DLC coated cutting tool.