Some aspects of microstructure damage to Cr–Mo–V rotor steel as a consequence of extremely long operation

The observed plasticity degradation of Cr–Mo–V heat resistant steel as a consequence of more than 20-year operation at 510 and 300$^{\circ}$C is caused by an increase in microdistortions of the crystalline lattice, density of dislocations, and sizes of mosaic blocks. The greatest variation of these microstructure properties in comparison with those for the initial state was observed for material operating at 300$^{\circ}$C. According to the data of acoustic emission in the variant of linear location with an increase in stresses of the second kind, there occurs accelerated formation of clusters, regions of local explosive plastic deformation. The clusterization should directly result in an increased probability of nucleation of an equilibrium mesocrack of millimeter range.