BORON-ENHANCED SINTERING OF IRON-MOLYBDENUM STEELS

摘要

Powder metallurgy steel compositions based on Fe-Ni-Mo-C mixtures provide a means to sinter to near full density and to high strength levels. Using a single press and single sinter process, maximum sintered densities near 7.2g/cm~3 were obtained. However, higher sintered densities can be attained through the addition of boron. This study examines two boron-modified alloy steels in terms of sintering densification with attention to the determination of mechanical properties. One route considered mixed elemental iron and molybdenum powders while a second route started with a prealloyed iron-molybdenum powder. In both cases, the powders were mixed with nickel, graphite, and boron. The difference in initial homogeneity in the molybdenum distribution impacted interaction with the boron, resulting in significant differences in densification and a large disparity in final mechanical properties, due primarily to grain boundary formation of borides in the mixed elemental compositions.