The Effect of the Si Alloying Method on the Microstructure and Properties of Sintering and Hardening of Gray Iron

The aim of this work is to study the effect of two sources of Si on the harden gray iron microstructure of a Fe–1.92%C–2%Si powder alloy. The alloy with distinct contents of alloying elements was prepared by two methods: the first mixing the masteralloy densmix as a C source and elemental Si powder and the second was by mixing the masteralloy densmix as a C source and the master alloy ferrosilicon as a Si source. The sintered microstructure of the alloy when using ferrosilicon as a Si source had graphite flakes surrounded by globular carbides that were precipitated at previous ferrosilicon sites, as well pearlite phase that separated the islands of globular carbides. However, the sintered microstructure of the alloy when using elemental Si did not have any globular carbides. The microstructures of the hardened gray iron of the alloy when using ferrosilicon as a Si source were found to contain plate martensite with little or no microcracks; however, the microstructures of the hardened gray iron of the alloy when using elemental Si contain coarser plate martensite with microcracks.