Although the phenomena of stress corrosion cracking is known to occur in 316L stainless steel in chloride environments, there is little knowledge regarding the incubation stage, i.e. when the cracks are very short and about a few grains in length scale. The project aimed to determine whether Grain Boundary Engineering GBE, through thermo-mechanical processing, could improve resistance to transgranular chloride stress corrosion crack nucleation in austenitic stainless steels. The material studied is type 316L austenitic stainless steel, with cracking developing in conditions of controlled humidity at 80°C under saturated MgCl2 salt deposits. Three batches were used; as received (AR), Heat treated at 950ºC designated as TM950ºC, treated at 1075ºC; designated as TM1075ºC and also treated at 1150ºC; designated as TM1150ºC for modifying the structure. The thermo mechanical treatment resulted in increase of ∑(3-29) and ∑3 in both fractions by almost 20% as the annealing temperature increased between 950ºC to TM1150ºC, on the other hand (AR) has sustained on 10% improvement over the TM950ºC in both fractions CSL% = ∑(3-29) and ∑3.In-situ observations show that the short cracks may grow to larger scale length in the (AR), TM950ºCand TM1150ºC than can grow in TM1075ºC.DIC analysis was not suitable for testing in this environment might be due to many factors, such as salt content residual effects, evaporation of the salt liquid, surface detritions and lateral movements due to tensile testing. The interaction between short stress corrosion cracks and microstructure was characterised by Electron backscatter diffraction (EBSD). The high angle grain boundaries (HAGB) are shown to act as barriers to cracking resulting in hindering or deviating the crack tip, which slows the overall crack growth rate. The type of microstructure that would have superior TGSCC resistance would be that, possess much higher fraction of both fractions CSL%= ∑(3-29) and ∑3.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:694311 |
| Date | January 2016 |
| Creators | Eltaghoor, Fathi Mohamed Abdsalam |
| Contributors | Stevens, Nicholas |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/transgranular-stress-corrosion-cracking-of-316-l-stainless-steel-in-chloride-environment-at-80-c(15a19dc4-cae1-4ae1-959e-9dbe45c58e19).html |
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