In-situ determination of austenite and martensite formation in 13Cr6Ni2Mo supermartensitic stainless steel

摘要

In-situ analysis of the phase transformations in a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) was carried out using a thermo-magnetic technique, dilatometryand high temperature X-ray diffractometry (HT-XRD). A combination of the results obtained by the three applied techniques gives a valuable insight in the phase transformations during the austenitization treatment, including subsequent cooling, of the 13Gr6Ni2Mo,supermartensitic stainless steel, where the magnetic technique offers a high accuracy in monitoring the austenite fraction. It was found by dilatometry that the austenite formation during heatingtakes place in two stages, most likely caused by partitioning of Ni into austenite. The in-situ evolutionip of the austenite fraction is monitored by high-temperature XRD and dilatometry. The: progress of martensite formation during cooling was described with a Koistinen-Marburger relation for the results obtained from the magnetic and dilatometer experiments. Enhanced martensite formation at the sample surface was detected by X-ray diffraction, which is assumed to be due to relaxation of transformation stresses at the sample surface. Due to the high alloy corrtent and high thermodynamic stability of austenite at room temperature, 4vol.% of austenite was found to be stable at room temperature after the austenitization treatment