Failure Analysis of Flue Gas Turbine Blade

The fracture of flue gas turbine blade of a refinery was analyzed by means of chemical composition analysis,hardness test,fracture surface observation and metallographic examination.The results show that the fracture feature of the blade was early fatigue fracture,and the failure was caused by improper forging process.Fatigue cracks originated from the grain boundaries at the exhaust edge of the blade.Coarse grains and a large number of grain stripes as well as chain carbides along the grain boundaries decreased the blade material strength and toughness,and accelerated the crack initiation and propagation that resulted in the fracture of the turbine blade under alternating stress.