Effects and mechanisms of constraint on creep crack growth behavior of GH3535 alloy.

• The constraint effects and mechanism on the creep crack growth of GH3535 alloy under the condition of W/B variation and constant were investigated. • Wedge cracking is the dominant form of crack initiation. • The deformation of the thick specimen is larger, which inhibits the wedge-shaped crack initiation. • Samples with small W/B or initial load are prone to crack branching. To clarify the influence of constraint effects on the creep crack growth behavior and mechanism of GH3535 alloy, creep crack growth tests on compact tension (CT) specimens of various sizes were performed at 650 °C. To reduce dispersion and more clearly compare the crack growth rate and crack initiation time under different constraints, an incremental polynomial was used to obtain the fracture parameter C * and the crack growth rate. Then the fracture parameter C * were used to correlate the crack growth rate and crack initiation time, respectively, and their relationships in double logarithmic coordinates were obtained. The results show that both the crack initiation time and the crack growth rate are affected by the constraint at the crack tip but remain linearly related to the fracture parameter C * in log–log scales. The essence of the constraint effect is that the structure hinders the plastic deformation of the crack tip. If the constraint is large, the plastic deformation corresponding to the crack tip will be small. However, the deformation accompanying the crack propagation of the alloy in this study will increase with increasing constraint. The crack growth rate at the middle thickness of the plain specimen without side grooves is greater than that at the near surface, and the crack profile is inverse parabolic shape, whereas the crack profile of the side-grooved specimen is relatively uniform. [ABSTRACT FROM AUTHOR]