11.6.2012 Pressing & Sintering

The Effect of Microstructure on the Machinability of PM Materials

Sinterhardening is currently being used in the powder metal (PM) industry to meet the demands of high performance components. The alloys used for sinterhardening produce a predominately martensitic microstructure when subjected to rapid cooling. This martensitic microstructure can be challenging to machine due to the particle hardness of the martensite. If the cooling rate is not sufficient, a mix phase microstructure of bainite and martensite will be produced. This mixed phase structure can be equally challenging to machine due to the differences in particle hardness. In this paper, two common sinterhardening alloys (FL-5305 & FLC2-4808) are subjected to two different cooling rates (0.5 °C/s & 2 °C/s) to understand the effect of microstructure on turning and drilling performance. This effect along with options for improving the machinability of these alloys will be discussed.