Effect of cryogenic quenching on microstructure and microhardness of rapidly solidified grey cast iron

Cryogenic processing has significant effect on longevity of iron-based machinery, automotive and aviation components. It affects entire cross-section of components and it is inexpensive compared to other treatment. In this study, the effect of deep cryogenic treatment (-195 °C) on the inter-relationship of structure, processing and property evolution of rapidly solidified commercial grey iron powders have been investigated. Droplets were prepared via containerless solidification processing using drop-Tube technique. The rapidly cooled droplets range from ≥ 850 μm to ≤ 53 μm diameters corresponding to cooling rate of 200 - 23,000 K s- 1. As a result of high-undercooling, there were significant retained austenite in relatively all the droplets. Hence, a comparative analysis on sample cryogenically treated and those that were not cryogenically quenched were examined. Microstructure evaluation were made by optical and SEM while XRD and TEM were used for confirmation of evolved-phases. Microstructure examination results shows cryogenic quenching facilitated irreversible transformation of retained austenite to martensite. Hence this presentation will show-case the conclusion effect on the samples microhardness.