Effects of environment on crack growth behaviour of superalloys under various loading conditions

Abstract

The influence of the environment on subcritical crack growth in nickel- and nickel–iron-base superalloys has been summarized. The examples of loading studied were fatigue and creep; creep–fatigue interactions were also examined. It was found that aggressive environments can either accelerate or retard crack growth. Crack retardation was caused mainly by local reduction in the driving force arising from crack deflection, crack branching, and oxide induced closure. The diffusion of, for example, oxygen along grain boundaries can accelerate crack growth. In some cases, it was possible to describe creep–fatigue interactions in terms of fatigue with hold times, using linear summation of creep crack growth and fatigue crack growth. However, exceptions to this were also found.

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