A segment from a premium-quality H13 tool steel die for die casting of aluminum failed after only 700 shots. The segment was subjected to visual, macroscopic, hardness, and metallographic testing. The investigation revealed that failure occurred as a result of fatigue at an electrical-discharge-machined surface where the resulting rehardened layer had not been removed. This rehardened layer had cracked, providing a source for fatigue initiation.
An AISI D2 tool steel insert from a forming die used in the manufacture of automotive components failed prematurely during production. Results of various analyses and simulation tests indicated fatigue failure resulting from improper heat treatment. The fatigue fracture originated because of a highly stressed condition produced by a sharp corner combined with low toughness from ineffective tempering. It was recommended that 25 other inserts that belonged to the same die be double tempered.