Microstructural analysis of IN617 and IN625 oxidised in the presence of steam for use in ultra-supercritical power plant
journal contributionposted on 2014-07-24, 13:59 authored by David M. Gorman, Rebecca HigginsonRebecca Higginson, H. Du, G. McColvin, A.T. Fry, Rachel ThomsonRachel Thomson
The nickel based alloys IN617 and IN625 that have been selected for their candidacy in the construction of the hottest regions of the supercritical steam cycle have been oxidised under isothermal conditions at 750 °C and atmospheric pressure in atmospheres of 100 % steam, 50/50 % steam/argon and air for up to 4,200 h. Both alloys developed a thin protective oxide under each condition. Scale thickness measurements using SEM micrographs were performed and showed that exposures in steam exhibited a higher rate of scale formation than exposures in air in both alloys. IN617 developed an extensive internal network of alumina which resulted in the formation of alloy protrusions into the scale altering scale growth kinetics, IN625 also formed alumina to a lesser extent. Voids formed in the matrix below the scale in both alloys in each environment. The extent of alumina formation alters the void morphology which eventually impacts the scale growth rate as inward scale growth occurred into the voids in IN625 but not in IN617.
We would like to acknowledge financial support from both EPSRC (Grant No. EP/G037345/1) through the Doctoral Training Centre in Efficient Fossil Energy Technologies and Alstom Power Ltd. We would also like to express our gratitude to the National Physical Laboratory for supplying the steam exposed materials with the support of the UK Department for Business, Innovation and Skills.
- Aeronautical, Automotive, Chemical and Materials Engineering
Published inOXIDATION OF METALS
Pages553 - 566 (14)
CitationGORMAN, D.M. ... et al, 2013. Microstructural analysis of IN617 and IN625 oxidised in the presence of steam for use in ultra-supercritical power plant. Oxidation of Metals, 79 (5-6), pp. 553 - 566.
Publisher© Springer Science+Business Media
- AM (Accepted Manuscript)
NotesThis article was published in the journal, Oxidation of Metals [© Springer Science+Business Media]. The final publication is available at Springer via http://dx.doi.org/10.1007/s11085-012-9342-2