Influence of chemical composition on the microstructure and phase transformations of Fe-14Cr ferritic steels

Mickaël Dadé (1) , Joel Malaplate (1) , Jean-Christophe C Brachet (1) , Thomas Guilbert (1) , Caroline Toffolon (1)

1 LA2M - Laboratoire d'Analyse Microstructurale des Matériaux

The effect of strengthened elements (Y2O3 and TiO2) on the microstructure has been investigated in Fe-14Cr-1W based ferritic steels. Titanium content and/or volume fraction of yttria range between ~ 0 up to 0.3 wt%. The volume fraction of nanoparticles is shown to control the grain size whereas titanium content has a significant influence on the chemical homogeneity. Martensite phase was obtained on a Fe-14Cr-1W based ferritic steel after consolidation by Hot Isostatic Pressing because of a higher content of carbon. A relationship between martensite phase and chemical heterogeneities was evidenced showing a chemical partitioning phenomenon. This phenomenon was also observed on ODS ferritic steels containing a low content of titanium (≤0.05 wt%) however microstructural parameters, such as size and volume fraction of nano-precipitates and grain size, are shown to delay the formation of martensite during cooling by decreasing the value of critical cooling rate. Thermodynamic calculations indicate that the minimal titanium content to get a microstructure with 100% of ferrite is about 0.09 wt%.

Keywords: ODS ferritic steel; Chemical heterogeneities; Partitioning; Martensite

Domains: Material chemistry

Mickaël Dadé, Joel Malaplate, Jean-Christophe C Brachet, Thomas Guilbert, Caroline Toffolon. Influence of chemical composition on the microstructure and phase transformations of Fe-14Cr ferritic steels. Materialia, 2019, pp.100388. ⟨10.1016/j.mtla.2019.100388⟩. ⟨cea-03238498⟩