Observation of the reversible stabilisation of liquid phase iron during nitriding

Abstract

Confocal scanning laser microscopy has been used to observe in-situ cooling of Grade 1 iron whilst under a nitrogen atmosphere. Liquid iron has been stabilised to temperatures below 1400°C through nitriding at high temperatures. This has been achieved in two ways. Firstly by exposing the melt to nitrogen and observing the onset of solidification whilst cooling. Secondly, under isothermal conditions by re-melting of initially nitrogen free iron at 1400°C through the introduction of a nitrogen atmosphere. The latter process has been shown to be reversible with liquid iron being unstable once reverting back to a helium atmosphere.