A Study Of Elevated-temperature Creep Evaluation In P91 Steel

In the present paper,different methods of magnetic detection,X-ray diffraction and hardness measurement were used to characterize the creep behavior of P91 steel under various conditions to evaluate the creep behavior of service components.Firstly,the high temperature mechanical properties of P91 steel was studied by elevated uniaxial tensile test under different temperatures.Then the complete creep curve and fracture time were obtained by the creep test under given conditions.Subsequently,the various creep damage samples were prepared by the interrupted test.Finally,various methods of magnetic detection,X-ray diffraction and hardness measurement were introduced to characterize different creep behavior of samples with the related parameters.Combined with metallographic and fracture tissue observation to verify the accuracy of parameter characterization.The main research contents and conclusions are as follows:1)The ultimate tensile strengthth ?b,yield strength ?0.2,Young's modulus E and elongation ? of P91 steel at 600? and 620? were measured by elevated uniaxial tensile test.The complete creep curves and creep lifetime were obtained under conditions 600?/175MPa and 620?/145MPa by the elevated temperature creep rupture test.And also obtained the time of interrupted tests to prepare the creep damage samples.2)Magnetic detection,X-ray diffraction measurements and Vickers hardness measurements results showed that with the increase of the life fraction,the magnetic parameters of coercivity(Hc),remanence(Br)and maximum permeability(?m),the full width at half maximum(FWHM)and dislocation density(p),and the hardness all showed"up-down" trend.Combined with metallographic and fracture tissue observation to verify the accuracy of parameter characterization.3)By Analyzing above three detection methods,it showed that the magnetic parameters are affected by the chemical composition and structure of the material easily,and the measurement is simple,but the characterization parameters are not sensitive to the evolution of material internal structure under short-term creep damage.X-ray diffraction method is more mature which is suitable for applications where the stress changes abruptly.However,this method is limited to the damage state to the surface of the component,and it is to some extent detrimental to human health.Vickers hardness detection method is simple,but hardness is an indirect parameter reflecting the evolution of material within the organization and material properties,generally used as a reference index.Based on above analyses,magnetic detection,X-ray diffraction and hardness measurements used in the present paper achieved characterization of different creep behavior of P91 steel.Especially,magnetic detection could directly reflect the state of dislocation and precipitation phase,which can further characterize the damage of P91 steel during creep process.