Creep-Fatigue Interactions in P91 Steel

Abstract To determine and quantify the influence of creep-fatigue interactions on the crack behaviour of P91 steel creep-fatigue crack growth (CFCG) tests were carried out with holding times up to 60 minutes and compared to results from fatigue crack growth (FCG) and creep crack growth (CCG) tests. It was found that the introduction of a holding time influences the crack initiation time but not the crack propagation. With holding times of 60 minutes, the difference between CCG and CFCG tests is very small. To characterise the fracture mode metallographic analyses were performed on selected specimens after CFCG tests. The crack path is inter-granular and an area of high cavity density was identified around the crack tip in all specimens. By comparing CFCG, FCG and CCG results, it can be finally noticed that specimens with a holding time of 6 and 60 min show a similar crack growth rate as samples under creep loading