Secondary Machining of Powder Metallurgy Components
Graham Smith, Guy Littlefair,
Abstract
Powder metallurgy (PM) technique has been known for the capability of producing near-net-shape parts. Its specific characteristics have resulted in low cost and eliminating many secondary machining. However, more and more PM parts do require additional operations to fulfill 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 PM components. The special feature in PM structure is the porosity in which can decrease the machinability and shorten the tool life. Different variables have been considered in the machinability of PM materials. Densities and free machining additives manganese sulfide are the two main factors of material composition, which dominate the PM machining performance. Machining process is the main method that generates the desired working surface of machining components.
This paper will discuss the metallurgical structure of the powder metallurgy components, their physical properties and possible issues when encounter machining operation. Turning operation has been tested in this investigation to show the relationship between the cutting speed, federate, cutting forces and chip formation. This investigation also discusses how the free machining additive, manganese sulfide, affects the PM structure and machinability. To understand how the metallurgical structure can affect the machining operation and how to obtain the optimized surface results.
Keywords:
Powder metallurgy, Manganese Sulfide, Porosity, Machinability, Cutting Forces
