Structure–property correlation of sub-zero treated AISI D2 steel

The present study deals with the establishment of relationships between microstructural parameters and properties of AISI D2 steel subjected to conventional heat treatment and different types of sub-zero treatments (SZTs) like cold treatment, shallow cryogenic treatment and deep cryogenic treatment. Assessment of microstructural parameters includes estimations of the amounts of different phases and stereological parameters of secondary carbide (SC) particles, while evaluation of mechanical properties comprises of determinations of bulk hardness, microhardness, fracture toughness and wear resistance. Structure–property correlations assist to establish that (i) the reduction of retained austenite content with concurrent increase in the amount of SCs by SZTs result in moderate increase of bulk hardness and microhardness of the matrix with marginal loss of fracture toughness but significant improvement in wear resistance, and (ii) the enhancement of hardness and wear resistance of the selected steel with decreasing temperature of SZTs is directly related to the continued increase in the amount and population density of SCs, but is inverse functions of their size and interparticle spacing.

► Microstructure and properties of different sub-zero treatments (SZTs) is correlated. ► SZTs, specifically deep cryogenic treatment, significantly enhance wear resistance. ► SZTs moderately increase hardness and marginally reduce fracture toughness. ► Variations of properties by SZTs are correlated with changes in the phase contents. ► Hardness and wear resistance show good relationships with carbide characteristics.