Study On High Temperature Corrosion Behavior And Life Prediction Of T92 Steel Used In Power Station Boiler

With the rapid development of China's economy,the demands for electricity are lasting increase,and thus the operating parameters of ultra super critical thermal power generating units are continuously improved,and thus the safety performance of steel for thermal power units need to reach a higher goal.Fireside corrosion resistance is an important safety index for selecting of heat-resistant steel.In addition,high temperature strength and long service life is also very important for high temperature component running in such bad environment.T/P92 steel is a typical representative of the "third generation of martensitic heat-resistant steel" and is quickly becoming preferred material on high temperature component of China's ultra super critical unit from 2006 for its excellent performance and low prices.Firstly,the high temperature corrosion behavior of T92 steel coated with sulfate,chloride and coal ash at 625 ? and 675 ? was respectively examined by XRD,SEM,EDS and kinetic curve of weighing.The results show that corrosive on the surface has obvious acceleration to high temperature corrosion of T92 steel,which followed the order of chloride salt >sulfate >coal ash.The composition of the corrosion products are mainly Fe2O3 and Cr2O3 with complex oxide generating.Besisdes,the effects of high temperature corrosion on the mechanical properties of T92 steel at high temperature and room temperature were examined by measuring the mechanical property indexes such as strength,percentage elongation,reduction of area,stress-strain curve,fracture morphology,microstructure and hardness.The results show that the strength of T92 steel decreases obviously at high and room temperature,and the hardness and strength decrease with the increase of corrosion temperature.The elongation of some specimens increases with the improvement of corrosion temperature,and the fracture mode is also related to corrosion temperature.The life prediction of T92 steel is preliminary discussed in the end of this paper.Based on the Manson-Succop parameter method,the T92 steel life prediction model has been established.Compared with the published data of ECCC.The predicted maximum allowable stress was slightly smaller than the measured value which indicating predicted value is reliable.The influence of high temperature corrosion on the creep life of T92 Steel has been analysed in terms of temperature and stress.The theoretical calculation shows that the effect of corrosion scale attached on the outer wall fireside on tube temperature can be neglected.High temperature corrosion will reduce the outer diameter of the tube,so the reduction of equivalent stress need to be considered when calculating the remaining life of T92 steel tube.