Browsing by Author "Morar, N."

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    Chlorine-induced stress corrosion cracking of single crystal superalloys at 550 °C
    (Springer, 2024-08-05) Duarte Martinez, Fabian; Dawson, Karl; Tatlock, Gordon; Leggett, J.; Gibson, G.; Mason-Flucke, J. C.; Nicholls, John; Syed, Adnan; Morar, N.; Gray, Simon
    This study has investigated the effect of NaCl and different gaseous environments on the stress corrosion cracking susceptibility of CMSX-4 at 550 °C. The presence of SOx leads to the rapid dissociation of NaCl into Na2SO4 and the release Cl2 and HCl, which then trigger an active oxidation mechanism and stress corrosion cracking. The incubation time for crack initiation at 690 MPa and in the presence of a sulphur containing environment is 10 min. A working hypothesis is that stress corrosion cracking occurs due to the hydrogen released at the oxide/alloy interface when metal chlorides are formed; however, this hypothesis needs to be further explored.
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    The effect of trepanning speed of laser drilled acute angled cooling holes on the high temperature low cycle corrosion fatigue performance of CMSX-4 at 850°C
    (Elsevier, 2017-05-04) Morar, N.; Roy, Rajkumar; Mehnen, Jorn; Nicholls, John R.; Gray, Simon
    The effect of laser trepanning speed and, as a result, recast layer thickness on the high temperature corrosion fatigue behaviour of CMSX-4 superalloy acute angled holes was investigated. The experimental test results show that an increasing laser drilling speed caused a reduction in corrosion fatigue life by 30-50% at 850°C, under low cycle fatigue regime. This reduction was found to correlate directly with the recast layer thickness and surface anomalies within the recast layer produced during the laser drilling process. Corrosion had a smaller effect on the overall life of the laser drilled specimens under the conditions tested. The results presented show that laser trepanning speedis influencial in limiting the life performance of laser drilled components in service.