Research On Creep Behavior And Life Prediction Model Of Heat-resistant Stainless Steel Used In Power Station

With economic development and increasing energy tensions,higher requirements have been placed on the efficiency of thermal power generation.309 S austenitic heat-resistant stainless steel and X10 Cr Al Si18 ferritic heat-resistant stainless steel are the main materials of superheater and reheater tubes,and their creep life is the decisive factor for safe use.In order to systematically study the creep behavior of 309 S and X10 Cr Al Si18 heat-resistant steel,this paper established a power law creep equation by uniaxial creep test,and based on the isotherm extrapolation method,Larson-Miller parameter method,and modified ? projection Method and creep damage model Kachanov-Robatnov(K-R model)performs life prediction analysis and damage analysis on creep test results.The main research contents and conclusions of this article are as follows:(1)Creep tests were conducted on 309 S and X10 Cr Al Si18 heat-resistant steels at 700?,800?,850?,900? and 650?,700?,750? and 800?.309 S heat-resistant steel obtained creep curves with three characteristic stages at 700?/100 MPa and 800?/50 MPa,and the longest creep life of 700?/100 MPa is 480.129 h,and the apparent activation energy of creep is 413.978 k J /mol.The X10 Cr Al Si18 heat-resistant steel obtained creep curves with three characteristic stages under the conditions of 700?/15 MPa and 750?/10 MPa.The creep rupture times were 491.449 h and 356.049 h,and the apparent activation energy of the creep was 188.42 k J/mol.The creep stress index of 309 S heat-resistant steel at 700°C,800°C,900°C and X10 Cr Al Si18 heat-resistant steel at 700°C and 750°C are all greater than 4,the creep mechanisms are all dislocation type creep,and its creep fracture the modes are both intergranular and transgranular mixed fracture.(2)Based on the phenomenological model isotherm extrapolation method and Larson-Miller parameter method,the creep life prediction models of 309 S heat-resistant steel at 700?,800?,900? and X10 Cr Al Si18 heat-resistant steel at 700? and 750? were established.The C value in the Larson-Miller parameter method is 20,and the polynomial nonlinear fitting is adopted.The predicted life of 309 S heat-resistant steel at 800?/45 MPa is 231.7h,the actual life is 249.79 h,the relative error is 7.23%,and the prediction accuracy is relatively higher.(3)Based on the modified ? projection method and creep damage K-R model,the creep life prediction models of 309 S heat-resistant steel at 700?,800?,900? and X10 Cr Al Si18 heat-resistant steel at 700? and 750? were established.Using the modified ? projection method to predict the creep curve and life of 309 S heat-resistant steel at 800?/45 MPa,when the strain is 26.45% in the third stage of creep,the relative error between the predicted creep time and the test creep time is only 2.9%.Compared with the Larson-Miller parameter method,the modified ? projection method can predict not only the creep life but also the creep curve,with higher accuracy and stronger safety and reliability.The creep damage K-R model is used to predict the creep life of 309 S heat-resistant steel at 700?/130 MPa.The relative error between the predicted creep time and the test creep time is 8.74%,the error is within 10%,and the prediction accuracy is high.