Fatigue and stress cracking is the direct consequence of changing mechanical stresses. Mechanical cycling of components or surfaces can result in local crack initiation and growth. This can cause catastrophic component failure or localized pitting, such as that often seen on gear faces.

Generally, this is best solved by mechanical redesign. However, diffusion treatments, such as nitriding are very effective in increasing fatigue life through the introduction of compressive stresses. Thermal spray coatings, especially HVOF, can introduce compressive stresses within the coating that can be used on components exposed to high stress cycling.