The Role of Manganese on Microstructure of High Chromium White Cast Iron

To determine the effect of austenite stabilizer element on the microstructure and behaviour of as–cast high Cr white cast iron Fe-21Cr-3Ni-1.7Mo-2.4C, different percentages of Mn (0.4, 0.9, 1.3, 1.7, 2.2 and 2.6 wt%) were added. Detailed investigations were carried out using scanning electron microscopy, energy dispersive spectroscopy analysis (EDS), X-ray diffraction and hardness test. It showed that with increasing Mn addition, the austenite phase (γ) of the as-cast alloys refine clearly. The morphology of the austenite phase for all alloys is a mixture of dendrite and plate like. The austenite phase refines clearly with increasing manganese addition. The major carbide phase formed in the as- cast alloys is M7C3 with minor carbides of (Fe,Cr)23C6 and Mo2C. Microstructure analysis showed the presence of small amounts of martensite and delta ferrite in all as-cast alloys. The hardness was decreased continuously with increasing Mn content. This is mainly attributed to the morphology of carbides rather than to small variation in carbides content. It was observed that considerable amounts of Mn were found in the carbides lower than that in the austenite matrix.