Application of Microdiffraction in Sem for Assessing Intrinsic Materials Susceptibility to Intergranular Corrosion and Stress Corrosion Cracking

Intergranular degradation processes (e.g., corrosion, stress corrosion cracking) are a frequent cause of premature and unpredictable service failure of engineering components. Since these processes cause component failure via propagation through the intercrystalline network, they are strongly dependent upon the distribution of specific grain boundary structures in the material. Previous studies have shown that grain boundaries crystallographically described by low Σ (Σ≤29) Coincidence Site Lattice (CSL) relationships can often selectively display a high resistance (and often immunity) to corrosion and fracture. Recent advances in automated microdiffraction techniques (e.g., EBSP) in SEM have now made it possible to readily evaluate grain boundary character distributions in conventional polycrystalline materials. by utilizing this technique, and by formulating and applying simple stochastic models for the propagation of intergranular cracking and corrosion processes, the opportunity now exists for (1) improved component lifetime prediction, and (2) the optimization of materials synthesis techniques to yield intergranular-degradation resistant microstructures.