Role of high temperature corrosion in life assessment and microstructural degradation of Cr-Mo steel weldments

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Abstract

The paper examines the relevance of recent data on high temperature corrosion of chromium–molybdenum steel weldments to new vistas of life assessment of high temperature components by scale thickness measurement. Also, results are presented of a study to investigate the combined roles of the nature of the oxidising environment and of secondary precipitation on the extent of void formation in the weldments of a chromium–molybdenum steel. Samples of microstructurally different regions, viz., weld metal, heat affected zone (HAZ) and base metal, were separated from the weldments of 2.25Cr–1Mo steel and oxidised in environments of steam and air. The resulting oxide scales and the region immediately beneath were characterised systematically using surface analytical techniques. Extensive internal oxidation and oxidation-induced void formation were found to occur during steam oxidation, with a much greater intensity in the case of the HAZ sample. The behaviour has been attributed to the role of a rather specific combination, and complex interplay, of the environment, the alloy microstructure, the oxidising temperature and the nature of the resulting external scale in establishing and sustaining internal oxidation. The results indicate a significant role of the steam environment in preferential cracking of the HAZ of the steel weldments.
Original languageEnglish
Pages (from-to)117-123
Number of pages7
JournalInternational Journal of Pressure Vessels and Piping
Volume77
Issue number2-3
DOIs
Publication statusPublished - 2000

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