Assessment of the Fatigue Cracking Impact and Optimization of Operating Conditions of a Hydraulic Hammer Anvil

Two main cracks appear on the upper end of the inner hole of a hammer anvil after 130 hours’ impact. The fracture morphology, microstructure, metallographic microscopy results and nonmetallic inclusions of the cracked anvil are analyzed. The chemical composition and mechanical properties of the anvil are examined. In its material, carbon content is shown to be higher than the highest limit of 40CrMnMo specifications, with multiple sulfide inclusions, which affects the comprehensive mechanical properties to some extent. The cracks originate from mechanical fatigue, propagating from the stress concentration point near the upper end of the inner hole. Low material toughness and high local working stresses are the main contributors of fatigue cracking. The lines of optimizing the operating conditions and improving the anvil structure and material are put forward.