Failure analysis of overheated coil leakage in ethylene cracking furnace

•The cracking failure of the finned tube in the convection section of the ethylene cracking plant was analyzed.•The methods of preventing the cracking failure of the finned tube in the convection section were proposed.•The initial source of cracking was induced by the thermal stress in the welded joint.•The cracking was induced by the combined effect of corrosion fatigue and intergranular corrosion.•The welding of straight tube sections of finned tubes should be avoided.•Reducing the C content of the tube or adding Ni content to the tube can prevent intergranular corrosion.