Browsing by Keyword "Nickel base alloy"
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Item Influence of the level of damage on the high temperature fatigue life of an aircraft turbine disc(2009-03) Silveira, E.; Atxaga, G.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationThis paper analyses the effect induced by those scratches produced during the handling and mounting of an aircraft turbine disc on their fatigue life. Fatigue tests were performed at 300 and 600 °C on specimens without and with various levels of damage. At 600 °C, an inverse relationship between the depth of the scratches and the fatigue life was found. However, at 300 °C no effect of these scratches on fatigue life was detected, obtaining very similar results in all of them. Examination of the failed specimens revealed that failure originated away from the scratch. Measurement of residual stresses helps to find an explanation to this apparently anomalous behaviour. It was observed that machining of the specimens induced high tensile residual stresses. At 600 °C, these stresses are relieved and failure at the scratched zone is promoted.Item Study on the root causes for the premature failure of an aircraft turbine blade(2009-03) Silveira, E.; Atxaga, G.; Erauzkin, E.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationA study on the root causes of the premature failure of a set of blades belonging to the high pressure turbine of an aircraft engine has been carried out. These blades were manufactured using a precipitation hardened nickel base alloy. The study consisted in a fractographic analysis by scanning electron microscopy and a microstructural examination by optical and scanning electron microscopy, identifying those phases which were present by means of X-ray energy dispersive spectrometry. Fractographic analysis revealed that failure of the first blade was due to thermo-mechanical fatigue, initiated at the internal cooling cavities. The presence of large size, cracked, hafnium and tantalum primary carbides on the fracture surfaces indicates that they have played an important role on the failure process, accelerating it. The other blades failed later by the impacts of the fragments lost from the first one.