Cyclic corrosion crack resistance curves of certain vessel steels

Abstract

ant layer, damage may occur in the facing [4] and, consequently, contact of the working medium with the vessel pearlitic steel is possible. This in combination with the very severe service conditions of water-cooled-water-moderated power reactors (low loading frequency, high cycle stress ratio, increased temperature, etc.) accelerates corrosion fatigue failure. Statistically [5] it has been established that 30-40% of all damage to power unit high-pressure vessels is related to the formation of corrosion mechanical cracks, pits, pitting, and other defects. Growth of such defects is significantly intensified under the combined action of force loads and the liquid medium, which may lead to failure of the reactor veseel. Therefore, in the design stage of a water-cooled-water-moderated power reactor it is very important to determine the probability of occurrence of such a danger during its design operating life. For this purpose and also for designation of the preventive maintenance schedule of the reactor, data on the rules of corrosion fatigue crack development in vessel steels taking into consideration the actual service conditions is necessary. The primary material for production of reactor vessels is 15Kh2MFA (water-cooled-watermoderated power reactors up to 440 MW) and 15Kh2NMFA (1000-MW water-cooled-water-moderated power reactors) steels [6-9]. At present their cyclic crack resistance in air has been most studied [10-22], while there is practically no information on crack resistance in the working medium. In connection with this a program of cyclic corrosion crack resistance tests was developed and carried out using a new method [23].