Authors: A Almathami E Elhachmi M Brochu
Publish Date: 2008/05/01
Volume: 43, Issue: 10, Pages: 3452-3458
Abstract
Alcontaining nanostructured coatings provide excellent protection from high temperature corrosion Aluminum oxide scales generally provide better oxidation resistance and yield lower oxidation rates than other oxide scale compositions In this study nanocrystalline 316L stainless steel containing 6 wt Al was synthesized using cryogenic milling cryomilling Complete alloying was obtained after 32 h of milling and the average grain size was found to be 7 nm High temperature thermal stability and oxidation kinetics of the alloyed powders were examined The powder demonstrated good grain growth stability at 500 °C at which point the powders had been heat treated for 120 h and the average grain size was found to be 114 nm The oxidation kinetics of the powder were studied for 48 h at 500 800 and 1000 °C respectively For comparison conventional 316LSS powder was also tested Nanocrystalline 316LSS6 wt Al showed lower weight gain than the conventional 316LSS powders During the oxidation of nanocrystalline 316LSS6 wt Al at 500 °C protective aluminum oxide scale formed at the surface At 800 °C and 1000 °C most of the nanocrystalline 316LSS6 wt Al particles showed completed outer aluminum oxide scale However at 800 and 1000 °C some particles showed growth of chromium oxide scale underneath the aluminum oxide scale In those samples Al depletion was also observed due to a nonhomogenous distribution of Al during cryomilling The activation energy of the oxidation reaction was calculated and was found to be affected by the enhancement of the grain boundary diffusion in nanostructured particles
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