Effects of deep cryogenic treatment for tungsten carbide‑iron cemented carbide

Abstract

This study aims to clarify the effects of deep cryogenic treatment of WC–Fe cemented carbide. WC–10 wt% Fe cemented carbide is fabricated using spark plasma sintering method and is cryogenically exposed to liquid nitrogen (‐196 °C) at a 1, 6, 12, 24, and 48 h sequence. Depending on the deep cryogenic treatment duration, the phase constituent is related to martensitic transformation (γ-fcc to α-bcc), causing a carbide–binder alloy phase (Fe3W3C or Fe6W6C; η-phase) between the deformation of the lattice structure and segregation from the WC/Fe interface. The mechanical properties of WC–Fe subjected to deep cryogenic treatment show that the hardness strengthens until 6 h (21.33 GPa) and then weakens after continued deep cryogenic treatment from 12 h (18.28 GPa). However, subsequent deep cryogenic treatment for more than 24 h recovers their mechanical properties to those observed initially. The variation in properties indicates a relationship between the grain growth behavior of cemented carbide and the formation of secondary phases induced by dislocation motion for martensitic transformation.