Effect of Heating Rate and Phase Transformation on the Dimensional Control of Ferrous PIM Compacts

Abstract

Powder injection molded (PIM) parts usually show large amounts of shrinkage after sintering due to the low powder loading, resulting in poor dimensional stability. This problem is further aggravated when a high shrinkage rate occurs or when the furnace temperature is not uniform. To alleviate this dimensional control problem, the effects of the phase transformation, sintering temperature, and heating rate were investigated. The results show that when an abrupt volume change occurs, as happens during the ! phase transformation of iron, the dimensional stability deteriorates. This problem gets worse when the density of the part is low. By slowing down the heating rate in the region where the high shrinkage rate occurs, avoiding the phase changes, and adding alloying elements to broaden the temperature range of the phase transformation, the dimensional control of ferrous PIM compacts can be improved.

Improvements in sintered density and dimensional stability of powder injection-molded 316L compacts by adjusting the alloying compositions

“…Since the SDs were quite small after molding, solvent debinding, and thermal debinding, the differences must have been caused by the heating rates. These results agree with the findings for sintered iron compacts [20].…”

Effect of sintering parameters on the microstructure and compressive mechanical properties of porous Fe scaffold fabricated using 3D printing and pressure less microwave sintering

“…The same behavior for iron was also discussed by the few researchers in the previous research. 35,36 This effect is also evident from the EBSD images, as shown in Figure 13. It can be deduced that a higher fraction of fine grain size was obtained in sample sintered at a slower heating rate of 5 ℃/min, and is reduced as the heating rate increased.…”

Effect of heating mode and sintering temperature on the consolidation of 90W–7Ni–3Fe alloys

“…It is envisaged that the fast heating rates achieved through microwaves restrict the W-W bond formation prior to melting and thereby making the contribution to densification from rearrangement more effective. Elsewhere too, researchers [44][45][46] have proposed that slow heating rates are detrimental to rearrangement. Fig.…”