Effects of (Cr,Fe)(2)B borides on hardness in powder-injection-molded product fabricated with Fe-based alloy powders

Abstract

In the present study, a powder injection molding (PIM) product containing (Cr,Fe)(2)B borides was fabricated with Fe-based alloy powders, and its microstructure and hardness were investigated in relation with volume fraction of (Cr,Fe)(2)B. In the Fe-based alloys designed by the thermodynamic calculation, the volume fractions of (Cr,Fe)(2)B increased with increasing (X-cr+ X-B) value, and were well matched with those obtained from the thermodynamic calculation. The hardness of the Fe-based alloys linearly increased with increasing volume fraction of (Cr,Fe)(2)B. When Fe-based alloy powders were injection-molded and sintered at 1165 degrees C, a densified microstructure with almost no pores was obtained. In the sintered microstructure, 56 vol% of (Cr,Fe)(2)B borides, together with a few pores (porosity; 0.5%), were relatively homogeneously distributed in the tempered martensite matrix, which resulted in the very high hardness over 600 VHN. Such a high hardness suggested that the present Fe-based alloy powders could be readily adopted for fabricating PIM products or for replacing conventional stainless steel PIM products. (c) 2012 Elsevier B.V. All rights reserved.