Mechanism of Fe2C Type Eutectic Carbide Formation Within Damascus Steel Structure

Abstract

Three stages are developed for forming a Damascus steel structure of high-purity white cast iron BU22A obtained by vacuum melting. In the first stage of the production process, a continuous of carbide sheath is formed along the boundaries of austenitic grains, which morphologically resembles ledeburite inclusions. In the second stage of the process, there is compaction and faceting of large eutectic type carbide formation. In the third stage of the production process (forging), a globular sorbite matrix is formed with faceted eutectic carbides in size from 5.0 to 20 μm distributed unevenly in the deformation direction. It is observed that the stoichiometric composition of faceted eutectic carbides is within the limits of 34 < C < 36 at.%, which corresponds to Fe₂C type ε-carbide with a hexagonal close-packed lattice. A two-stage mechanism is considered for conversion of excess secondary cementite into faceted Fe₂C type eutectic ε-carbides. It is revealed that isothermal exposure duration on heating to the eutectic temperature, is an integral part of the process of forming new excess Fe₂C type carbides with a hexagonal close-packed lattice.