Diffusion

· Gas turbine blades are subjected to high temperatures and tensile stresses due to their rotational velocity. Directional diffusion under the influence of the stress field causes the blade to change its dimensions via Creep.
· The defect migration paths around a single grain in the blade structure are illustrated. Atom motion elongates the blade in the direction of the tensile stress. Removal of grain boundaries increases blade life.

From: Howmet Corporation, and Newey and Weaver, "Materials, Principles and Practice," Butterworth (1990)