Energy-based approach to thermal fatigue life of tool steels for die casting dies

• An experimental method is proposed to evaluate thermal cracking of mould steels.
• Energy-based fatigue life model is formulated by accounting the test period.
• Thermal cracking is closely related to the dissipated energy at material points.
• The proposed life model enables accurate evaluation of thermal fatigue cracking.

Thermal fatigue cracking is one of the mostly encountered failure mechanisms for die halves in the die casting industry. This is due to rapid alternating heating and cooling of die surfaces during the casting process. In this paper, an experimental thermal fatigue test method based on cyclic induction heating and water cooling is proposed for the evaluation of thermal cracking of the tool steel used in the industry. An energy-based fatigue life model is formulated by accounting the test period. Finite element models are developed for better understanding of thermal loadings experienced by samples under the fatigue testing. The results demonstrate that thermal cracking is closely related to inelastic energies dissipated at the material levels. The outcome of this study enables accurate evaluation of crack growth and, thus, evaluation of thermal fatigue life of die casting dies by using the proposed energy-based model.