Communication Dans Un Congrès Année : 2017

The Effects of Nitrogen on Kinetics and Products of Austenite Decomposition in Low-alloy Steel

Résumé

In order to better understand the effect of nitrogen on austenite decomposition in low alloy steel, specimens of 23MnCrMo5 homogeneously enriched in nitrogen, carbon or a mix of both were isothermally transformed at temperatures ranging from 200°C to 750°C. The transformation progress was monitored in situ by HEXRD and post mortem microstructures were characterized using SEM and TEM, including HRSTEM and ACOMTEM. At all temperatures, nitrogen reduces the incubation time of the transformation of austenite into ferrite and speeds up its completion. High volume fractions of CrN, both inter-and intragranular, were observed at all temperatures with different morphologies and very wide size distribution. It has also been shown that other nitrides precipitate during the various stages of the treatment, notably AlN, VN and MnSiN2. In nitrogen containing specimens transformed above BS, ferrite forms as equiaxed grains with interspersed pearlite islands. Between BS and MS, ferrite occurs as entangled laths featuring an extremely high density of nanotwins. The entanglement of the microstructure is reminiscent of acicular ferrite, albeit at a much finer scale, and it is thought to result from the particle stimulated nucleation of ferrite on CrN. As a comparison, bainite obtained in specimens containing carbon only was coarser, not entangled and did not show any twinning.

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Dates et versions

hal-01898584 , version 1 (18-10-2018)

Identifiants

  • HAL Id : hal-01898584 , version 1

Citer

Hugo P. van Landeghem, S.D. Catteau, J. Teixeira, J. Dulcy, M. Veron, et al.. The Effects of Nitrogen on Kinetics and Products of Austenite Decomposition in Low-alloy Steel. FiMPART 2017, Jul 2017, Bordeaux, France. ⟨hal-01898584⟩
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