ISSN:
1460-2695
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract— The growth rate of fatigue cracks in two single crystal nickel base superalloys, CMSX-6 and SRR99, along the 〈001〉 planes are presented and rationalised in terms of two interacting crack propagation mechanisms: one attributed to crack tip plastic blunting and the other attributed to the brittle failure of the oxide scales. The role of the oxide scale is twofold as it also wedges the crack and modifies the blunting term through a crack closure effect. On the other hand, a positive effective stress intensity range is required to fracture the oxide scale. Fatigue tests were carried out at different temperatures (500 to 1050°C), frequencies (0.001 to 20 Hz), cycle waveforms and load ratios (0 to 0.9), with starter crack lengths of abut 100 μm. The model predictions match the crack growth rates obtained for both materials. Even though both materials are nickel base superalloys, they have very different oxidation behaviours. CMSX-6 has an improved oxidation resistance over SRR99, however, because of the twofold nature of the oxidation process, which material provides the better life expectancy depends on the applied test temperature and loading cycle.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1460-2695.1997.tb00307.x
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