Nonmetallic Inclusions in 08Kh18N10T Steel as the Cause of Initiation of Defects in Heat-Exchange Tubes of Steam Generators of Nuclear Power Plants

Abstract

We present the results of investigation of the microstructure of 08Kh18N10T steel in heat-exchange tubes after their long-term operation in steam generators of WWER-1000 power-generating units. We study the influence of nonmetallic inclusions on the degradation of the metal of heat-exchange tubes at the nuclear power plants. It is shown that nonmetallic inclusions located on the metal surface serve as a possible cause of the violation of passivation of the metal and the initiation of corrosion defects. Under the influence of operating factors, alternating stresses are formed in the metal, which leads to microfracture on the inclusion–metal interface and to the development of corrosion fatigue.