Investigation on influence of dynamic strain ageing on fatigue crack growth behaviour of modified 9Cr–1Mo steel

Fatigue crack growth behaviour of modified 9Cr–1Mo steel is examined in the temperature range 300–823 K. An improvement in fatigue crack growth resistance is observed in the dynamic strain ageing regime. The activation energy for the process leading to this is estimated from the temperature-dependence of crack tip strain rate as 55–80 kJ/mole. This indicates that dynamic strain ageing due to interaction of dislocations with interstitial solute elements is responsible for the improved fatigue resistance in this range.

► Fatigue crack growth behaviour (FCG) of P91 steel is examined at 300–823 K.
► FCG resistance increases with temperature in the range 623–723 K.
► An activation energy for the process leading to this is estimated as 55–80 kJ/mole.
► Dynamic strain ageing due to carbon-dislocation interaction is responsible for this.