Thermal Fatigue — Glossary Entry

Thermal Fatigue is a specific failure mode where repeated heating and cooling of the cutting edge grows micro-cracks that eventually chip the edge. Thermal fatigue is the dominant failure mode on high-speed tissue and film slitting without active cooling.

Visual tells

• A “network” of micro-cracks visible under 10× magnification, parallel to the edge
• The first chip is usually at the high-wear point of the edge (often the centre)
• Edge temperature can be inferred from the colour: straw (200–250 °C) → blue (300 °C) → purple (400 °C)

Fixes

• Apply a hot-hardness coating (TiAlN, AlCrN, CrAlN)
• Switch to a hot-hardness steel (M2 with TiAlN, M35, M42)
• Add active cooling (air or water-mist) aimed at the cut zone
• Verify the hone is ≥ 10 µm on a high-speed line

See also.