Ni-base single crystal alloys exposed to high temperatures in air may experience a variety of damage mechanisms, each of which has its specfic damage accumulation rate. The most common mechanism is diffusion with inward diffusion of oxygen, and outward diffusion of the lighter alloying elements such as aluminum. Fick’s law can be used to describe the dynamics of this process resulting in the classical parabolic rate law for damage accumulation.
Jet engines may be exposed to environments containing small amounts of sulfate dust during take-off or landing. In this case, a more aggressive damage process has to be considered, as the sulfate may considerably accelerate material degradation. A model is proposed which adds an additional source term to the classical diffusion equation leading to an almost linear increase in time of the damage surface layer. A non-linear temperature dependence of this type of damage process can be derived on the basis of statistical considerations.It was found that experimental results obtained by aging small sulfate doped specimens at high temperatures can be very well reproduced with the developed model.