Quantitative investigation on the crack evolution behavior for creep-fatigue test of CrMoV steel welded joint

The artificial interrupted creep-fatigue test was carried out to quantitatively investigate crack initiation and propagation rate of the CrMoV steel welded joint at 520 degrees C. The evolution of crack and the role of oxide could be clarified clearly by several stages. A crack of 1.6 mu m length initiated on the oxide in the first 10 cycles. Then, crack propagated inside the oxide layer with a low rate, forming a periodic multilayer bamboo-like structure. Meanwhile, further oxidation resulted in deepening of oxide notches. Finally, cracks penetrated the oxide with a rate of 50 mu m/cycle into the matrix resulting in the rupture.