Influence Mechanism of Rare Earth Inclusions on Fatigue Crack Initiation and Propagation of Heavy Rail Steel

ABSTRACT This paper introduces the influence of the depth, shape, and size of inclusions on crack initiation in RE (La, Ce) rail. A very novel auxiliary strain measuring fixture and an interesting precrack innovative method are used to study the crack and strain at the sharp corner of inclusions. With the increase of RE content (wt%) from 0.030% to 0.130%, the density and size of inclusions first decrease and then increase. The shape of inclusions tends to spheroidize first and then sharpen. Cracks initiate at the sharp corners of long, triangular, irregular, and shallow, large (> 20 μm) inclusions. Precrack deeper than the wear layer will promote the formation of a spiral plastic flow zone at the crack tip and the merger of multiple cracks. These findings provide new insights into the relationship between microstructural features and cyclic loading that could lead to different mechanisms of noninclusion‐induced crack initiation.