The effect of powder particle size on sintering and hardenability

An ability to calculate the hardenability is built on the assumption that alloying elements are distributed evenly. This assumption is realistic for wrought steels, but questionable for PM steel: time allocated to sintering may not be sufficient to homogenize the alloying concentrations. Using prealloyed powders resolves the problem, but such mixtures typically demonstrate poor compressibility. During sintering of admixed powder blends many mechanisms affect the mass transfer. In fact, it can be so complex that no industrial methodology has been implemented to numerically simulate alloying element distribution in sintered PM steels [1]. It is intuitively clear that with smaller particles of Fe sintering time can be reduced to reach uniformity to alloying elements. An experiment was designed to investigate the effect of Fe-powders' sizes on hardenability. Results were quantified by comparing Jominy curves of Fe-C-Cr-Mn-Mo-Ni PM steel composed of three different size distributions of Fe powder.