Corrosion fatigue behaviour of high V–Cr–Ni cast irons in 3%NaCl aqueous solution

Corrosion fatigue behaviour was studied on high V–Cr–Ni cast irons with different microstructures. Rotary bending fatigue tests have been performed using smooth specimens in 3%NaCl aqueous solution. In 3%NaCl aqueous solution, the fatigue strengths were nearly the same as those in laboratory air in short life regime, but fatigue failure took place at applied stresses below the fatigue limit in laboratory air. Corrosion pits extensively generated at vanadium carbides (VCs), within lamellar microstructure, and at the boundary between those phases and austenitic matrix microstructure. Fatigue cracks were initiated relatively much earlier due to the growth and coalescence of corrosion pits, but subsequent crack growth was considerably slower than in laboratory air due to complicated crack path.