Wongpromrat, Patthranit
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Wongpromrat, Patthranit
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patthranit.wo@kmitl.ac.th
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Item type:Publication, Evidence for chromium, cobalt and molybdenum volatilisations during high temperature oxidation of Co-27Cr-6Mo Alloy(2022-07-01); ; Ponpo, PhisanA Co-27Cr-6Mo alloy was oxidised in pure O<inf>2</inf> between 800 and 1000 °C for durations up to 96 h. The flow rate was varied between 2 and 5 cm.s<sup>–1</sup>. In these conditions, volatilisations of chromium, cobalt and molybdenum were observed. The chromium volatilisation values were in good agreement with calculations assuming (CrO<inf>3</inf>)g volatilisation limited by diffusion in the gas boundary layer. On the contrary, the measured flux of evaporated Co was higher than the calculated Co volatilisation flux from the metallic Co. The theoretical relation between the solid Co particle size and its vapour pressure was suggested to help explaining such difference. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Xps analysis of oxide formed on the surface of co-28cr-6mo-1si alloy oxidized at 550 ºc(2020-01-01); ; ; Chiba, AkihikoThis work investigated the influence of oxidation durations on the formation of oxide on the surface of wrought Co-28Cr-6Mo-1Si alloy. The iso-thermal oxidation was individually performed in air at 550ºC for 4, 12 and 24 h. For comparison, the surface of the non-oxidized Co-28Cr-6Mo-1Si alloy was concurrently examined. The chemical compositions of the non-oxidized and oxidized alloys were principally analyzed via X-ray photoelectron spectroscopy (XPS). The XPS results revealed that the surface of the non-oxidized alloy enriched in Cr-oxide. After oxidation treatment, the Co-oxide, existing as Co<sup>2+</sup> state was observed coexisting with two Cr-oxide states, Cr<sup>3+</sup> and Cr<sup>4+</sup>. The low concentrations of Mo<sup>6+</sup> were also observed on the oxidized alloy surface. With the increase in oxidation durations, the Co-oxide was suppressed by Cr-oxide. The XPS depth profile analysis indicated that the thickness of the oxide film increased with increasing the oxidation duration.