THERMAL FATIGUE IN HOT WORK TOOL STEELS - A REVIEW

The Thermal Fatigue is an important mechanism of  failure that occurs in materials and equipment subjected to hot work, which strongly influences the surface quality, productivity and life of tools and dies. The thermally induced mechanical stresses lead to nucleation of network cracks on the material surface, which propagates due to the continuous application of thermal cycles. Such situation may result in the failure of the tools, as it occurs, for example, in aluminum injection dies. Different approaches have been made to study the possibility of delaying the occurrence of cracking induced by thermal fatigue.  In recent years, researchers have tried to evaluate the process to understand it and to quantify the basic processes of damage evolution promoting reliably lifetime prediction of tools and components under given process parameters. The properties of hot work tool steels are strongly dependent on the correct heat treatment and surface engineering methods applied to this kind of components. Thermal fatigue behavior has direct influence from the combined effects of microstructure and mechanical and physical properties of tool steel. This review contributes to a better understanding about failures by thermal fatigue in hot work tool steels commonly used which underwent different heat treatments.