Meaning
The formation of cracks in metal dies or mold cavities caused by repeated cycles of heating and cooling during production. Engineers analyze thermal fatigue cracking to select die materials that can withstand the temperature extremes of die casting and forging. This failure mode is limited to high-temperature operations and excludes cold metal forming.
Wear Degradation
Repetitive heating and cooling cycles cause localized expansions and contractions that generate high internal stresses within the tool steel. These thermal cycles eventually lead to the formation of microscopic cracks on the surface of the mold. The progression of thermal fatigue cracking leads to cosmetic and dimensional defects on the cast parts.
This degradation requires the tool to be pulled for repair.
Failure Mechanism
The severity of the damage depends on the temperature range and the cycle time of the process. If the tooling steel lacks high thermal conductivity or toughness, the cracks can propagate rapidly and lead to catastrophic failure. Regular inspections help detect thermal fatigue cracking at an early stage before the mold is ruined.
This early detection is necessary for maintaining high yields on the line.
Surface Protection
Advanced surface treatments and cooling channel designs are deployed to minimize the effects of thermal stress. Coating the tool with thermal barriers or optimizing the layout of the cooling channels helps reduce the temperature fluctuations on the surface. These measures, combined with the correct choice of tool steel, significantly reduce the risk of thermal fatigue cracking.
This approach extends the useful life of the mold and ensures consistent part quality.
