Isothermal and non-isothermal oxidation kinetics of nanooxide dispersed high Cr ferritic steel prepared by mechanical alloying

摘要

Oxidation kinetics based on Kissinger-Akahira-Sunose analysis of high Cr ferritic steel synthesised by mechanical alloying of elemental powder blend of 84Fe-13.5Cr-2.0AI with 0.5 nano-Y_2O_3 (all in wt-%) dispersion followed by cold compaction with 250 MPa pressure and sintering in vacuum (10~(-6) mbar) at 1000°C for 1 h have been investigated under isothermal (600-900°C for up to 50 h) and non-isothermal conditions (50-1200°C with heating rates of 10, 20, 30 or 40°C min~(-1)). Mechanism of oxidation was taken place by counterionic transport of oxygen from surface to interior and cations (Cr~(3+)/Fe~(3+)) from the interior to the surface through grain boundary at low oxidation temperature (~600°C) and through grains at high oxidation temperature (700-900°C). Early formation of Cr rich spinel layers on the surface improves the oxidation resistance by acting as the diffusion barrier against counterionic transport of ions during oxidation.