Effect of cyclic waveforms on cavitation propensity of P91 steel weld joint at 873 K

P91 is a 9Cr-1Mo ferritic-martensitic steel which is used as steam generator (SG) material for fast reactor applications. Construction of SGs involves several weld joints (WJs) that are weak links also in the structure. Application of various types of cyclic loading and creep combinations can lead to different responses of the P91 steel WJ and thereby the resultant fatigue life. The scope of the present work is to identify the deformation and damage under the effects of various combinations of creep-fatigue interaction (CFI) waveforms. Towards this, location-specific damage has been assessed through various particles present in the steel and their cavitation propensity and severity to cause final failure under the effects of various fatigue-creep combinations. First time, it is demonstrated through 2D hardness mapping that in an unsymmetrical CFI loading waveform, short creep hold has more damaging effects in the form of strength loss as against the longer strain or creep holds. Interestingly, whereas under unsymmetrical loading, the initial strength of the weld metal was either uniformly retained (30 min CH or 30 min TH) or uniformly lost (10 min CH, 10 min TH), under symmetrical loading (CC and 5 min TCH), only a part of the weld metal lost the initial strength and the rest of it retained.

Automated summary

This study aims to investigate the deformation and damage of P91 steel weld joints under different creep-fatigue combinations. Location-specific damage was assessed through evaluating the particles and their cavitation propensity in the steel, showing that short creep holds have more damaging effects on strength loss.