Characteristics of Retained Austenite in Cast GX70CrMnSiNiMo2 Alloy Tool Steel
DOI:
https://doi.org/10.24425/afe.2025.155358Abstract
Material wear strictly depends on hardness and microstructure, homogeneity of this microstructure in particular. The presence of retained austenite in the microstructure is not always the cause of the reduced wear resistance, though it is commonly believed that retained austenite has low hardness and is responsible for the accelerated wear of components. The aim of this study is to demonstrate that the hardness of retained austenite is similar to that of martensite and can even reach 900HV0.2, while its volume fraction, which for the tested alloy amounts to about 21%, depends to a very small extent only on the cooling intensity of the quenching medium. Reducing the cooling rate by quenching in air, when the cooling rate is the lowest, makes the volume fraction Vv of retained austenite increase to even 31%, while its hardness assumes the lowest value and decreases to slightly over 800HV0.2, similarly to the hardness of martensite, which decreases on average to approximately 850HV0.2. The occurrence of retained austenite and its high hardness should be associated with the primary segregation of elements such as Cr, Mo, Mn, Si, whose content assumes the highest values in the interdendritic areas.References
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