Heat checking as a failure mechanism of dies exposed to thermal cycles: A review

Abstract

The “heat checking” phenomenon, which occurs due to thermal fatigue, is one of the dominant mechanisms in shortening the lifetime of dies which undergo sequential in-service high- and low-temperature operating cycles. This phenomenon results in the formation of a network of microcracks on the surface, which deepens with further repetition of thermal cycles. The service lifetime of dies made of hot work tool steel is characterized by successive changes from high to low temperatures. Hot deformation processes are subjected to working temperatures above 300 °C. In order to increase the die lifetime, many studies have been conducted to understand the mechanism of crack formation and find ways of prevention. However, there is no comprehensive study on the effect of the die production process, e.g., from the steelmaking to the die manufacturing step. In addition, it is important to understand the effect of service conditions on “heat checking” occurrence. In the present research, a short overview of this phenomenon has been provided including the definition, formation mechanisms and characteristics of “heat checking”. In addition, the influence of the steel characteristics such as surface engineering, heat treatment and service conditions on the phenomenon is investigated. As the simulation and theoretical aspects of “heat checking” are extensively investigated and summarized and the lack of knowledge is mostly in experimental parts, in order to fill the existing gap, this overview is preferentially focused on and summarizes experimental literature outputs rather than theoretical ones.

Keywords

• Heat checking
• Fatigue
• Die
• Service lifetime
• Forging
• Extrusion