Machinability of As-Compacted P/M Parts: Effect of Material Chemistry 980635

Since the advent of P/M technology as a near net shape production process, millions of mechanical components of various shapes and sizes have been produced. Although P/M continues to be one of the fast growing shaping processes, it suffers from the inability to produce intricate geometry's such as internal tapers, threads or recesses perpendicular to pressing direction. In such cases application of machining as a secondary forming operation becomes the preferred alternative. However, machining of P/M parts due to their inherent porosity is known to decrease tool life and increase tool chatter and vibration. Consequently, several attempts have been made to improve the machinability of P/M materials by either addition of machinability enhancing elements such as sulfur, calcium, tellurium, selenium, etc., or by resin impregnation of P/M parts. However, due to the recent introduction of warm compaction systems such as ANCORDENSE™ which enable higher green strengths in as-compacted materials, it is now possible to explore the feasibility of machining production parts before sintering. Latest research on green machining shows promise of application of the process to production parts. This research is an attempt to investigate the machinability of four different materials with different material compositions. Responses like forces, torque, breakout, surface finish, and geometrical accuracy were monitored while drilling four different materials of nominal density 7.2 gm/cc. Results indicate machining forces, torque, surface finish and breakout can be reduced and optimized by the amount of nickel and molybdenum contents. These results are useful for both implementation of green machining technology as well as for improving the machinability responses of as-compacted P/M parts.


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