Effect of Cu addition on hardness and microstructural features of low alloy white cast iron

The aim of this work is to investigate in details the effect of Cu on hardening variation and microstructural feature of low alloy white cast iron. For this purpose, a wide variety of iron melts consisting of different weight percent Cu were prepared with step by step addition of about 0.5%Cu to a constant base chemical composition of low alloy white iron. Hardness measurements were supplemented with x-ray diffraction, colored light metallography and electron microscopy to follow the relationship between hardness and microstructure of as-cast white irons. The experimental results show that as-cast hardness has been sequentially increased from 49HRC to the values of 52, 57 and 61HRC with step by step addition of only about 0.5%Cu to the chemical composition of low alloy base melt iron, respectively. The remarkable improvement of as-cast hardness has been rationalized to the formation of more and more displacive martensitic phase transformation products developed as a consequence of alloying partitioning within the associated austenite and carbide during solidification. The M₃C eutectic carbide is just rich in Cr while the austenite phase, apart from a significant enrichment of Mn, Ni and Cu, has been surprisingly enriched from Mo as well. (paper)