Influence of Hardness and Carbon Content on Rolling Contact Wear in Pearlitic Steels

It has been reported that the characteristic of rolling contact wear of rail steels varies depending on the microstructure and carbon content of steels. However, the reasons for such variations have not been fully elucidated yet. Accordingly, the authors conducted two-cylinder rolling contact wear test by using pearlitic steels with carbon content in the range from 0.8 to 1.0 mass% and studied the effects of carbon content of pearlitic steels on the rolling contact wear. In addition, the authors examined the dominating factor of the rolling contact wear in pearlitic steels and the effects of carbon content on this factor. The main findings obtained are as follows: (1) The wear resistance of pearlitic steels improves with increasing carbon content. (2) The rolling contact wear of pearlitic steels is dominated by the rolling contact surface hardness (RCSH). (3) The improving wear resistance of pearlitic steels is attributable to an increase in RCSH due to raising work-hardening rate of the rolling contact surface with increasing carbon content. (4) The reason why the work-hardening rate of the rolling contact surface of pearlitic steel rises with increasing carbon content is considered as follows: An increase in the cementite density (carbon content) increases the amount of dislocation in the matrix ferrite and promotes the grain refinement of the matrix ferrite. Moreover, the solid solution of carbon in the matrix ferrite takes place due to the decomposition of cementite. As a result, the matrix ferrite is strengthened through the promotion of dislocation hardening, grain refinement and solid solution of carbon.