Topic: Effect of Microstructure on the Localised Corrosion and Atmospheric Stress Corrosion Cracking of 15-5PH Stainless Steel

Synopsis:
This work aimed to enhance the mechanistic understanding of pitting and atmospheric induced stress corrosion cracking (AISCC) of 15-5PH stainless steel by establishing links between microstructural features (here affected by changing the ageing temperature, 450 °C, 540 °C and 650 °C) and susceptibility to such phenomena. Microstructural evolution was characterised using STEM EDX and differences in pitting behaviours were assessed using double loop electrochemical reactivation (DL-EPR) which found a linear trend in degree of sensitisation with ageing temperature which correlated with the increase in the presence of Cr carbides. Electrochemical noise measured by galvanically coupling dissimilar microstructures suggests that the higher temperature ageing treatment, which produced the most metastable pitting events, may have a higher probability of transitioning to stable pitting. Four-point bend specimens with Cl- salt deposits exposed to controlled temperature and humidity revealed that higher ageing temperatures were more resistant to cracking. In addition the mode of cracking changed from an intergranular pathway in 450 °C specimens to mixed-intergranular and transgranular in 540 °C whilst no cracks were observed in samples aged at 650 °C.

Joint Meeting with TWI
(Evening Event)

Company: University of Manchester
Speaker: Alyshia Keogh

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