Failure analysis of an open die forging drop hammer

This paper analyses the failure of a large open die forging drop hammer. The analysis had to be semi-destructive as it was wanted to repair the equipment and to return it into service. A visual examination was performed at the forging shop and fatigue initiated at two internal defects blamed for the failure. A small sample was extracted from the fracture surface. Unfortunately, due to the desire of recovering the drop hammer this sample did not belong to those zones which were identified to be the origins of the failure but to the zone of progression of the crack by fatigue close to the overload final failure. Fractographic analysis by scanning electron microscopy revealed the presence of some ductile dimples pointing to an acceleration of the cracking process at this stage.