27th IFHTSE CONGRESS & EUROPEAN CONFERENCE ON HEAT TREATMENT 2022

AISI 304 austenitic stainless steel plates were austenitized in Ar or solution nitrided in 0.5 bar N2 gas at 1150 °C for 2 h. Both austenitized and solution nitrided conditions were cold rolled to different engineering strains by 10‒70 % thickness reduction. The most heavily deformed coupons were subsequently annealed at various temperatures for up to 1 hour. Gaseous nitriding of the deformed and the annealed steels was performed in ammonia/hydrogen gas mixtures at atmospheric pressure at different temperatures: 430 °C and 460 °C. The nitrided case was characterized with X-ray diffraction analysis, reflected light microscopy, electron microscopy and hardness testing. The influence of microstructural features as grain size and the deformation mode by martensite/twin formation and/or dislocation generation and dislocation glide, on the development of the nitrided case and microstructure of the expanded austenite zone is discussed.