Assessment of potential service-life performance for MarBN steel power plant header under flexible thermomechanical operations. (June 2020)

• Record Type: Journal Article
• Authors: Li, M.; Benaarbia, A.; Morris, A.; Sun, W.
• Is Part Of: International journal of fatigue. Volume 135(2020)
• Publication Date: 2020-06
• Subjects: MarBN steel -- Thermomechanical fatigue -- Unified viscoplasticity -- Superheater header -- Service-life assessment; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2020.105565
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: Strain-controlled fatigue test of MarBN are conducted over a range of temperatures. The strain dwell periods increase the softening behaviour and reduce fatigue life. A unified viscoplastic model is implemented to capture the deformation mechanisms. SWT approach is adopted to assess the service-life performance of MarBN component. Abstract: This paper is concerned with the service-life assessment of 9Cr steels superheater outlet steam header subjected to realistic subcritical and future ultra-super critical flexible operating conditions. The proposed methodology is achieved via a combined program of high temperature strain-controlled fatigue tests, temperature- and time-dependent unified viscoplastic model for thermomechanical fatigue analysis, and Smith-Watson-Topper critical plane criterion for multi-axial life prediction. Samples of idealised operational transients with particular attention on the starting-up cycle is fully coupled with the computational modelling of header component for the high temperature performance assessment. The predicted results indicate that: (i) the header shell inner-bore saddles at weld regions are the critical locations that lead to earlier potential fatigue crack initiation, and (ii) the predicted lifetime under subcritical conditions correlates reasonably with the industrial experience. A steam header manufactured from MarBN operating under ultra-super critical condition is shown to have comparable life performance with the P91 header operating under subcritical condition.