SCC Growth Behavior of Nickel-based Alloy 600 in Safe-end Welded Joints

Nickel-based alloys are commonly used as welding part for the primary circuit safe-end welded joints of pressurized water reactors. Due to the harsh service environment and uneven mechanical properties of the welded joints, the nickel-based alloys are prone to stress corrosion cracking, which has a great effect on the safe operation of nuclear power. To understand the effect of the material macrostructural parameters (including the plastic properties of the material and the stress intensity factor K) on the stress corrosion cracking (SCC) growth rate, the SCC propagation finite element model (FEM) of nickel-base alloy 600 under different macrostructure parameters was established, and the effects of different plasticity and K values on the plastic zone and tensile plastic strain around the crack tip were analyzed. Results show that the plastic zone size and tensile strain around crack tip are affected by K, yield strength and hardening exponent, among which the K at crack tip has a greater influence, and it is inversely proportional to yield strength, while the K is directly proportional to hardening exponent. According to the results of SCC growth rate calculated under different K and the experimental results under high-temperature water environment, the range of characteristic distance r(0) of nickel-based alloy 600 is obtained. The research results can provide a scientific basis for SCC rate prediction under high-temperature water environment of nickel-based alloy 600 for nuclear power plants.