Influence of high mean stresses on lifetime and damage of the martensitic steel X10CrNiMoV12-2-2 in the VHCF-regime
Martensitic 9-12% Cr-steels are widely applied in steam turbines.In the low pressure rotor blades,fatigue loadings at several 100 Hz induced by the inhomogeneous flow field behind the vanes are superimposed by high mean stress due to centrifugal forces.Using an ultrasonic fatigue testing machine and in-depth microstructure analyses,the present study investigates the influence of mean stresses at load ratios up to R = 0.7 on the VHCF behavior with an ultimate cycle number of 2·109.From R = -1 (no mean stress) up to R = 0.7 crack initiation changes consistently from the surface to internal inclusions at a cycle number around 4·107.Fractography indicates that fine grained areas around the inclusions only occur for R=-1.With increasing load ratio,fractures are observed at increasing cycle numbers.In spite of this fact and in spite of considerable cyclic creep at load ratios up from R = 0.5,the fracture mechanics approach proposed by Murakami consistently describes the lifetime behavior for load ratios up to R = 0.5 over 4 decades of lifetime.The contribution will give a comprehensive overview of these findings together with detailed microstructure studies of the fracture surfaces.
Cr steel turbine blade steel mean stress fatigue damage
Tilmann Beck Stephan Kovacs Lorenz Singheiser
Institute of Energy and Climate Research(IEK-2),Forschungszentrum Jülich,Jülich 52425,Germany
国际会议
北京
英文
1-10
2013-06-16（万方平台首次上网日期，不代表论文的发表时间）