Influence of Mean Stress and Defect Distribution on the High Cycle Fatigue Behaviour of Cast Ni-Al Bronze

Nickel Aluminium Bronze (NAB) alloys have been used extensively in marine applications such as propellers, couplings, pump casings and pump impellers due to their enhanced mechanical properties such as tensile strength, creep resistance and corrosion resistance. However, there have been several instances of in-service failures of the alloy due to high cycle fatigue (HCF). The present research aims at characterizing the HCF behavior of as-cast NAB at room temperature in the presence of casting defects by analysing the effect of variation in mean stress and the influence of size and location of defects on the HCF life of NAB. A significant decrease in the HCF life was observed with an increase in the tensile mean stress, irrespective of the defect size. Further, a considerable drop in the HCF life was observed with an increase in the size of defects and proximity of the defects to the surface. However, the surface proximity was seen to override the influence of defect size and maximum cyclic stress.