Browsing by Author "Leggett, A. J."
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Item Open Access Effects of oxidation and hot corrosion in a nickel disc alloy(2008-12-31T00:00:00Z) Encinas-Oropesa, Adriana; Drew, G. L.; Hardy, M. C.; Leggett, A. J.; Nicholls, John R.; Simms, Nigel J.This paper describes work to study oxidation and hot corrosion damage in nickel disc alloy RR1000. Oxidation damage has been characterised via mass change data from thermogravimetric analyses at temperatures from 700 to 800 ºC and cyclic oxidation testing at 700 and 750 ºC. Thin oxide scales rich in Cr and Ti have been found to grow in a parabolic dependence with time. Oxidation rate constants have been correlated with temperature using an Arrhenius equation. Through the use of simplifying assumptions, mass change data have been converted to oxide thickness values. These values have been compared with observed values of oxide scale and the depth of near-surface damage, which have been measured using focused ion beam (FIB) microscopy. Hot corrosion of RR1000 has been studied in the laboratory by ‘deposit' recoat experiments at 700ºC. In these tests, samples were coated with deposits of Na2SO4/NaCl salt in a gas stream of air-300 vpm SO2. Corrosion damage has been quantified by dimensional metrology of samples before and after exposure. This enabled metal losses, i.e. the depth of corrosion pits, to be determined. Distributions of metal loss data were then generated to produce median damage values and exceedance cumulative probabilities. Finally, the effect of contaminants on the hot corrosion resistance of RR1000 has also been evaluated.Item Open Access Influence of shot peening on high-temperature corrosion and corrosion-fatigue of nickel based superalloy 720Li(Taylor and Francis, 2016-04-08) Gibson, G. J.; Perkins, K. M.; Gray, Simon; Leggett, A. J.High-temperature corrosion fatigue, a combination of corrosion with a fatigue cycle, is an emerging generic issue affecting power generation and aero gas turbine engines and has the potential to limit component life. Historically, surface treatments, such as shot peening have been used to improve component life and have been optimised for fatigue response. Research into optimisation of shot peening techniques for hot corrosion and high-temperature corrosion fatigue has shown 6–8A 230H 200% coverage to provide overall optimum performance for nickel-based superalloy 720Li based on the limited data within this study. Utilisation of electron backscatter diffraction techniques, in combination with detailed assessment of corrosion products have been undertaken as part of this work. The resultant cold-work visualisation technique provides a novel method of determining the variation in material properties due to the shot peening process and the interaction with hot corrosion. Through this work it has been shown that all three shot peening outputs must be considered to minimise the effect of corrosion fatigue, the cold work, residual stress and surface roughness. Further opportunity for optimisation has also been identified based on this work.