Cracking and Fracture of Hot-Work die Steels

Summary

High-strain low-endurance fatigue tests have been carried out on notched specimens of four hot-work die steels loaded in three-point bending at room temperature and 350°C at two different loading rates. The effect of several parameters on crack initiation, crack growth rate and fracture has been studied.

The number of loading cycles to cause crack initiation is not significantly influenced by material, position of the test piece in the die block, hardness or specimen orientation. Preheating accelerates crack initiation particularly at low loading rates.

At room temperature crack growth rates for all materials and test conditions were similar. Preheating increased growth rates at low loading rates but had little effect at the higher loading rates.

Material composition affected brittle fracture. Preheating reduced the occurrence of fracture but increased hardness and a higher loading rate increased susceptibility to fracture.