The Mössbauer spectroscopy studies of ε to cementite carbides transformation during tempering of high carbon tool steel

Purpose: This work presents results of investigations using Mössbauer spectroscopy technique and their interpretation concerning transformation of ε to cementite carbides during tempering in relation to previously conducted dilatometric, microscopic and mechanical investigations. Investigations were performed on 120MnCrMoV8-6-4-2 steel. Design/methodology/approach: Samples taken from investigated steel were austenitized at the temperature of 900°C and hardened in oil. Austenitizing time was 20 minutes. After that, seven of eight samples were tempered. Tempering consisted of holding the samples at 200°C for defined periods. All the times mentioned above were selected basing on IHT (Isothermal Heating Transformations) diagram. Findings: The influence of the tempering time on nucleation and solubility of ε carbides, and on cementite nucleation and growth, was determined. Research limitations/implications: The analysis of phase transformations during various periods of tempering using Mössbauer spectroscopy technique made possible to reveal fine details connected with the processes. Practical implications: Optimum tempering time of tools made from the investigated steel should be in the range of 1.5-2h. Originality/value: Details descriptions of ε to cementite carbides transformation during isothermal heating from as-quenched state.