“…1,89 On the microstructural modification by cryotreatment Scientific investigations by now have established that cryotreatment can substantially improve the desirable properties and performance of tool steels. The improvements in the properties by cryotreatment have been attributed to one or combinations of the following microstructural alterations: (i) more complete transformation of austenite to martensite, 9,33,[68][69][70][71]79,90 (ii) alteration in the lattice parameters of the martensite like reduction in its tetragonality, 34,35,91 (ii) preferential precipitation of transition η-carbides, 73 (iii) precipitation of nano-sized carbide particles 92 and/or formation of nano-sized martensite particles, 58,60 and (iv) alterations in the decomposition of martensite leading to enhanced precipitation of refined SCs with more homogeneous distribution. 47,53,74,79,81,[93][94][95][96] Meng et al 73 have inferred that DCT promotes preferential precipitation of fine η-carbides (also referred to as ε ′ (ε), Fe 2 C, orthorhombic 97 ) instead of ε-carbide (Fe 2.4 C, hexagonal closed packed) which is responsible for simultaneous improvement in hardness and toughness, and, in turn, enhances WR of D2 steel.…”