Effect of W addition on the low cycle fatigue behavior of high Cr ferritic steels

Low cycle fatigue (LCF) behavior of 9Cr-1Mo steels containing different amounts of W has been investigated at room temperature and 873K. It has been found that the fatigue life increases with the increase in W content up to 1.8 wt.% at both temperatures. However, further increase in W up to 2.7 wt.% results in the deterioration of fatigue life, primarily due to the formation of soft delta -ferrite in the tempered martensite. Oxidation occurring at high temperature also deteriorates LCF properties, which is resulted from the formation of brittle oxide layers induced along the slip bands during cyclic deformation.