Effect and mechanism of out-of-plane constraint on creep crack growth behavior of a Cr–Mo–V steel

The effect and mechanism of out-of-plane constraint on creep crack growth rates were experimentally investigated. The results show that the out-of-plane constraint effect on creep crack growth rates is related to C∗-integral levels. In low C∗-integral region, with increasing out-of-constraint, there is a change in creep fracture mode from ductile to brittle intergranular fracture, which leads to the increase in creep crack growth rates. In middle and high C∗-integral regions, the constraint basically has no effect or slight effect on the creep crack growth rates. In creep life assessments, the effects of constraints and C∗-integral levels on the creep crack growth rates should be considered.

► Out-of-plane constraint effect on creep crack growth (CCG) rate is related to the C∗.
► Creep fracture mode and CCG rate change with out-of-constraint in low C∗ region.
► The constraint basically has no effect on the CCG rate in middle and high C∗ regions.
► Effect of constraint and C∗ level on CCG rate should be considered in life assessment.