Assessment of Damageability of Heat-Resistant Steels by the LM-Hardness Method Under Biaxial Cyclic Tensile Conditions

Results of experimental studies on 10GN2MFA and 15Kh2MFA heat-resistant steels as to the stressed state type effect on regularities of development of their damage are presented. These results took into account the maximum load cycle stress under cyclic creep conditions at temperatures of 20–350°C by the LM-hardness method. It is shown that at the beginning of plastic deformation resistance loss caused by decreasing cross-sectional area and strengthening module, the intensity of metal damage accumulation in the specimen under biaxial tension is higher than that in uniaxial tension. The limiting values of homogeneity coefficients, which correspond to the moment of the beginning of plastic deformation resistance loss of the steels under study, were obtained experimentally. The effect of the stressed state stiffness on kinetics of the damage at room and elevated temperatures was analyzed. A possible practical use of research results, based on a quite simple LM-hardness method, for evaluation of metal damageability during their operation is outlined for some heavy-duty components of NPP power equipment structures.