Failure Analysis of IEU Drill Pipes

Many 127.0 mm×9.19 mm IEU G105 drill pipes failea after 2 367 h of pure drilling time with 8 726 m of penetration footage.The service and loading conditions configuration dimensions,chemical composition,mechanical properties,metallography,macro-fractography,micro-fractography,and corrosion products of the drill pipes were anolyzed.Crack extending velocity of the drill pipe material in corrosion medium was also tested.The results,indicated that the fracfure of the drill pipe resulted from premature corrosion fatigue failure.The failure courses might be as follows: Corrosion pits occurred first at the internal surface in the stress concentrating area of the drill pipe,and then fatigue cracks initiated in pit bottoms,and fractured finally as cracks penetrated through the wall thickness of the drill pipe.The fracture was related to the configuration,material quality and load condition of the drill pipe.