OPTIMIZATION OF LIQUID-PHASE SINTERING OF BORON PM STEELS USING MASTER ALLOYS

摘要

Permanent liquid phase sintering represents an interesting strategy for obtaining high sintered densities. However, one common drawback of this approach is the formation of a brittle eutectic network resulting from the solidification of the liquid phase. Boron powder metallurgy (PM) steels are particularly sensitive to this problem. This work investigates the effect of the concentration of alloying elements (B, Mn, Ni, C, and prealloyed Mo) and cooling rate on densification, microstructure, and strength of boron PM steels prepared using different master alloys containing Fe-Mn-Ni-B-C. A detailed analysis of the effect of each factor led to the identification of a safe design zone that minimizes the formation of a brittle eutectic network, and thus its negative impact on strength. The latter approach made it possible to obtain high densities (> 7.3 g/cm(3)) and strength (TRS approximate to 1,950 MPa) with conventional sintering and a total concentration of alloying elements lower than 3 wt.%.