Corrosion pitting and environmentally assisted small crack growth

by Alan Turnbull

Proceedings AVolume 470(2169):20140254

September 8, 2014

©2014 by The Royal Society

Example of pitting and stress corrosion cracking on a tensile specimen of 3NiCrMoV steam turbine disc steel exposed to simulated aggressive condensate solution.

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Multiple crack evolution from a corrosion pit showing a scanning electron microscopy (SEM) image (a) and an XCT image (b) of a steam turbine disc steel specimen stressed at 90% σ0.2 and

exposed to simulated condensate at 90°C for 7173 h [25] (see electronic...

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Internal view of the pit-to-crack transition within a steam turbine disc steel specimen stressed at 90% σ0.2 and exposed to simulated condensate at 90°C for 668 h (the surface of the sites

rendered on the left are shown in the SEM image on the right for com...

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Internal view of pits and cracks in a specimen exposed to simulated condensate at 90°C for 2209 h; the surface of the site rendered in (b) is shown in the SEM image (a) for comparison [25] (see

the electronic supplementary material, video S3, for greater de...

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

SEM image (a) and XCT image (b) of a pit with two cracks apparently about to coalesce; specimen exposed to simulated condensate at 90°C for 2209 h [25] (see the electronic

supplementary material, video S4, for more detail).

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

FE analysis highlighting localization of plastic strain just below the mouth of a corrosion pit (a).

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Tilted SEM images of a pit in 316L stainless steel in a simulated oilfield environment; (a) before and (b) after FIB milling.

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

SEM images from two different FIB slices, formed by gallium ion milling to a depth of 20 μm, showing a corrosion pit mouth at the top of the image with cracks emanating from it [31].

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Image of galvanostatic droplet process for pre-pitting [35].

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Optical surface crack monitoring system with an image of a well-developed crack from a corrosion pit showing the probes for the potential drop measurement above and below the pit

[35].

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Comparison of fatigue crack growth rates for small, short and long cracks in a 12Cr martensitic stainless steel (FV 566) tested at 90°C in air with a loading frequency of 1 Hz and stress ratio of

0.05; (a) small crack depth determined using optical techniqu...

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Comparison of fatigue crack growth rates for small, short and long cracks in a 12Cr martensitic stainless steel tested at 90°C in aerated 300 ppb Cl− and 300 ppb SO42− at 90°C.

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Transverse cross section of 316L stainless steel coarse ground to Ra 0.8 μm.

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society

Residual stress of 316L stainless steel as a function of depth longitudinal (L) and transverse (T) to the long axis of the specimen for two different surface finishes (fine, corresponding to Ra 0.2 

μm, and coarse, 0.8 μm) using the incremental hole drilling...

Alan Turnbull Proc. R. Soc. A 2014;470:20140254

©2014 by The Royal Society