Subcase Fatigue

Subcase fatigue on a carburized gear. Photo courtesy GEARTECH © 2013.

Definition: Cracking in case hardened gears in transition zone between case and core.

Identification: Subcase fatigue results in the presence of fine longitudinal cracks and longitudinal craters with sharp, perpendicular edges.

Discussion: Subcase fatigue results when Hertzian contact stress exceeds the subsurface fatigue strength.

Prevention: Reduce Hertzian contact stress. Increase case hardness, case depth, and core hardness.

More Information: For more information on subcase fatigue, please submit a question to our “Ask an Expert” link. For assistance with a gearbox failure analysis, please visit our “Consulting” page.