Corrosion behaviour of Ni-Cr alloys in mixed oxidising gases at 650 °C. (September 2020)

• Record Type: Journal Article
• Authors: Jiang, Chengyang; Xie, Yun; Kong, Charlie; Zhang, Jianqiang; Young, David J.
• Is Part Of: Corrosion science. Volume 174(2020)
• Publication Date: 2020-09
• Subjects: Alloy -- Oxidation -- SEM -- High temperature corrosion; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2020.108801
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Steam changed the scale morphologies in low atmosphere, but slowed the scale thickening rate in high atmosphere. Volatilisation of chromia occurred in the presence of both water vapour and oxygen at 650 °C. No NiCr2 O4 spinel was formed at a detectable level in any gas mixture due to slow growth at 650 °C. The critical Cr content required for chromia maintenance varied with gas composition. Abstract: Binary Ni-Cr alloys containing 5−30 wt% Cr were exposed to Ar-20O2, Ar-20O2 -20H2 O, Ar-20CO2, Ar-20CO2 -20H2 O and Ar-20H2 O (vol.%) at 650 °C. In dry/wet O2, and dry CO2, 5−25 Cr alloys formed a three-layered structure: an external NiO layer, an inner oxide layer and an internal oxidation zone. The Ni-30Cr alloy formed a continuous chromia layer, with local outer NiO islands in dry/wet O2, but a continuous Ni-rich outer layer in dry CO2 . In wet CO2 /water vapour alone, all alloys underwent internal oxidation, nickel metal expulsion and NiO formation. Gas composition effects on the Cr concentration required for chromia formation are discussed.