Performance of High-Temperature Materials for Efficient Power Plants: The Waterside Challenge

Abstract

Supercritical (SC) service at high operating values aims for good plant efficiency, but the waterside oxidation resistance can then become life-limiting. In this paper, selected materials and modeling options are compared for life assessment under waterside SC oxidation, particularly for thermal power plants that increasingly need to accommodate cyclic service, fast ramping, and low minimum loads to an extent to which the conventional design practices and materials solutions only partially accounted. For example, the life reduction by high-temperature oxidation and corrosion via lost load-bearing wall thickness is more easily accommodated than the impact on crack growth or material ductility.

Oxidation model for construction materials in supercritical water—Estimation of kinetic and transport parameters

“…The expected service lifetime for fuel cladding is from 25 000 to 30 000 h (3 -3.5 years) depending on the design, which is roughly ten times longer than most autoclave tests have been. In order to have some estimate about the fuel cladding oxidation over the expected service lifetime, it is necessary to extrapolate data obtained from relatively short autoclave tests by assuming a particular model for the corrosion kinetics [113]. While this approach can be used to rule out proposed candidate alloys, longer tests are necessary to obtain the data needed to validate the extrapolations.…”

“…First of all, the candidate material must fulfil certain properties, but also the economic point of view needs to be taken into account. It is clear that a new material or modification of a new material has to show sufficient improvement to earn acceptance, in spite of the added (often alloying-related) investment [113]. However, there could be some drawbacks, e.g.…”

“…when adding new alloying elements to the bulk alloy or surface modification through coating or cold working. Although the criteria may be clear and competition from the existing solutions is well defined, it can be challenging to achieve significant improvement, e.g., because improving some property may require a disproportionately high level of additional expensive alloying, or because of conflicting trends in simultaneously required properties [113]. For example, it would be good for corrosion and oxidation resistance to have enough Cr in steels or increased defect density through cold working near the material external surface, since increasing Cr content in the bulk alloy or enhancing Cr diffusion to the material surface improves corrosion and oxidation resistance.…”

Modelling for Creep Cavitation Damage and Life of Three Metallic Materials

“…The decreasing opportunities to baseload operation and increasing need to support intermittent renewable supply have resulted in new patterns of accumulating damage. Therefore, it is challenging to reliably detect and evaluate the leading damage so that its progression and impact can be accurately characterised for life prediction [3][4][5][6][7][8][9][10][11][12].…”