Powder metallurgy (P/M) industry has been known for the capability of producing near-net-shape parts. Its specific characteristics have resulted in lower production costs and eliminating many secondary machining. However, more and more P/M parts do require additional operations to fulfil their complex geometry features and surface roughness.
Many of the machining factors that influence the machinability of cast and wrought steel parts, such as cutting speed, feedrate, coolant, 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. Material densities and the free-machining additive manganese sulphide (MnS) are the two main factors of material composition, which dominate the machining performance.
This paper will demonstrate the essential considerations of cutting parameters and the microstructure of P/M components. Turning operations have been tested to show the relationship between the cutting forces and surface finish. This study shows that the manganese sulphide powder can improve the machinability of these alloys under different machining conditions.