Creep damage and crack initiation in P92–BNi2 brazed joint

Abstract

Nickel-based brazed joints are widely used at high temperatures, and it is very important to ensure the creep strength. Using three-dimensional finite element method, this paper presents a study on the creep damage and creep crack initiation (CCI) in P92–BNi2 brazed compact tension (CT) joint specimen, and the effect of brazed residual stress on CCI has been investigated. Firstly, the as-brazed residual stress is simulated. Then the effect of residual stress on creep and damage is calculated by an uncoupled Norton equation and the ductility exhaustion approach. The results show that the CCI is a function of residual stress, load level, joint thickness and notch radius. The brazed residual stress has a great effect on creep damage, and it can lead to the initiation of creep crack lonely without any mechanical load. The combination of applied load not only accelerates the creep damage and decreases the CCI time, but also determines the creep crack propagation rate. The CCI time decreases with the increase of applied load and joint thickness. As the notch radius increases, the CCI time increases.