Multiscale 3D analysis of creep cavities in AISI type 316 stainless steel

Burnett, T. L.; Geurts, R.; Jazaeri, H.; Northover, S. M.; McDonald, S. A.; Haigh, S. J.; Bouchard, P. J. and Withers, P. J. (2015). Multiscale 3D analysis of creep cavities in AISI type 316 stainless steel. Materials Science and Technology, 31(5) pp. 522–534.

DOI: https://doi.org/10.1179/1743284714Y.0000000639

Abstract

A sample of AISI type 316 stainless steel from a power station steam header, showing reheat cracking, was removed from service and has been examined by a combination of microscale X-ray computational tomography, nanoscale serial section focused ion beam–scanning electron microscopy, elemental energy dispersive X-ray mapping and transmission electron microscopy. Multiscale three-dimensional analysis using correlative tomography allowed key regions to be found and analysed with high resolution techniques. The grain boundary analysed was decorated with micrometre sized, facetted cavities, M₂₃C₆ carbides, ferrite and G phase but no σ phase. Smaller intragranular M₂₃C₆ particles were also observed, close to the grain boundaries. This intimate coexistence suggests that the secondary phases will control the nucleation and growth of the cavities. Current models of cavitation, based on isolated idealised grain boundary cavities, are oversimplified.

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