The removal of oxygen during sintering by carbothermic reduction was studied for steel compacts Fe-Cr-Mo-C and Fe-Mo-C prepared from prealloyed powders. The compacts were prepared by pressing at 600 and 1000 MPa and sintering at 1100 and 1300°C in vacuum. It showed that for the Cr-Mo steel, deoxidation strongly depends on the sintering temperature, in contrast to the plain Mo steel; at 1300°C very low oxygen levels were measured with the standard density compact while at high density still significant oxygen is contained. This indicates inhibition of final deoxidation by pore closure, but apparently without adverse effect on the mechanical properties.

Powder grades pre-alloyed with 1.5-3 wt% chromium can be successfully sintered at the conventional temperature 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 , 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 , after sintering at followed by cooling at and tempering.