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As the geometric complexity and tolerance requirements of powder metal parts become more demanding added machining operations are required as a necessary step in the manufacturing process. Likewise, a better understanding of the effects powder metal materials and processes have on the machinability of P/M components is needed. An investigation into the effects of post-sintering cooling rate on the microstructure, machinability and tensile properties of an FC-0208 copper steel was conducted. Machinability was measured using a drill test on a high volume production component. Three cooling rates (9, 17 and 40 ° C/minute) were used to generate the variation in microstructure. Machinability analysis was performed using box-and-whisker plots and includes drill motor load, hole size on drill entry and exit, and microfinish. Metallography and tensile properties and a discussion of their relationship with machinability are included.

A multicompany research effort was initiated to develop characteristic properties of a powder metal steel relevant to fatigue design of structural components. A low-alloy steel with the composition 0.85 % molybdenum, 0.5 % carbon was tested in the quench hardened and tempered condition. Density effects were examined utilizing 7.0 g/cm3 and 7.4 g/cm3 material, and porosity size and shape effects were examined by varying the sintering temperature of the 7.4 g/cm3 material to promote pore rounding. Results indicate that increasing the density increased both the monotonic and fatigue properties. Increasing the sintering temperature to promote pore rounding further improved the fatigue performance at low strain amplitudes. However, at high strain amplitudes the beneficial effects of pore rounding were not realized due to the dominant effects of surface carburization.