Remaining Life Preestimate Of Gas Turbine Rotor

Gas turbine is the key equipment in petrochemical system production, the rotor operateslong-period in the condition of high temperature and corrosive gas. Sometimes unplannedovertemperature phenomenon occurs when gas turbine is operating, microstructure deteriorate,and that cause reduction of remaining life. In this paper, it investigates the microstructure andmechanical properties changes of gas turbine rotor material GH864 alloy in the condition ofsimulated overtemperature, and discuss the influence of the changes of microstructure to theremaining life of the material.The application of replica technique is researched in metallographic examination. It isobserved clearly the state of the boundary and the condition of Carbide precipitating in theboundary from the plastic replica which is made of AC paper extracting the microstructure ofalloy. The size and quantity and distribute ofγ'phase can be obtained exactly fromplastic-Carbon double replica which is produced with collodion extracting the microstructureand injecting Carbon.Standard heat treatment is carried out on gas turbine rotor blade, it makes theperformance retrieved some degrees. Overtemperature treatment of 800℃,850℃,900℃,950℃has been operated on the blade. It is shown from the research that, when rising theovertemperature, the quantity of carbide in the boundary decrease, the size and quantity ofγ'phase also reduces, so as the hardness of the alloy. Overtemperature treatment of 2～16hours has been operated on the blade. It is shown that, when prolonging the overtemperaturetreatment, the carbide of boundary doesn't change obviously, the size and quantity ofγ' phaseand hardness have a little downtrend. It indicated that the influence of overtemperature islarger than holding time to the properties of alloy. As strengthen phase, carbide phase andγ'phase have direct influence to the properties of alloy.High temperature tensile and high temperature stress-rupture test is carried out on the materialwhich treated under different overtemperature. Results shown that yield strength and tensilestrength reduce, also does persistent life as rising the overtemperature. The results of fracture surface analysis revealed that alloy shows character of intercrystalline cracking, with the hoistof temperature, dimple on the fracture increases, ductility improves.According analyzing and fitting test data, related curve between stess and rupture time isobtained, and the relation betweenγ'and remaining time can also be deduced.