| Inconel690 alloy is widely used as PWR steam generator tube material because of its excellent high temperature mechanical properties and corrosion resistance. The nuclear power station operating experience has shown that 690 alloy has corrosion fatigue failure tendency in PWR water. Thus it is necessary to study its corrosion fatigue performance.In this paper, the corrosion fatigue crack growth behavior of 690 alloy in saturated DO simulate PWR primary water and high purity water by compact tension specimen has been researched while the crack tip keeping in small scale yielding. The result shows:(1) The crack growth rate was determined by crack tip plastic zone^ load frequency and work environment. When the crack tip was under small scale yielding, it would form obvious plastic deformation. When it was in corrosion environment, this area was dissolved quickly to enhance the crack growth. In other wise, load frequency also had obvious influence.(2) The crack growth path was transgranular, and the breachs or deflection of crack would decelerate the growth rate, and then effected on the calculation result of Fen. The fracture had obvious corrosion fatigue features, it was composited of ridge areaćfatigue platform and microcracks. The crack propagated in three-dimensional space, and oxide could be observed in some area.(3) All the crack growth experiment showed that, the crack tip could form multiple crack cores under cycle load and expanded in the same time. And then the crack which was perpendicular to the load direction would grow into main crack, the others would become into breach cracks.(4) Statistical analysis showed that, the adverse effects caused by material inhomogeneities and measurement error of instruments could be effectively reduced by introducing of Fen. In saturated DO simulated primary water it had maximum 5 times accelerate relative to the rate in RT environment, while in the high purity water it was 4 times. |
PDF Full Text Request