26.9.2006 Pressing & Sintering

Influence of Sintering Parameters on the Mechanical Performance of PM-Steels Pre-alloyed with Chromium

Powder grades pre-alloyed with 1.5-3 wt% chromium can be successfully sintered at the conventional temperature 1120 °C, although well-monitored sintering atmospheres are required to avoid oxidation. Mechanical properties of the Cr-alloyed PM grades are enhanced by a higher sintering temperature in the range 1120-1250 °C, due to positive effects from pore rounding, increased density and more effective oxide reduction. Astaloy CrM (Fe-3 wt% Cr-0.5 wt% Mo) with 0.6 wt% graphite added obtains an ultimate tensile strength of 1470 MPa and an impact strength of 31 J at density 7.1 g/cm³, after sintering at 1250 °C followed by cooling at 2.5 °C/s and tempering.