Fatigue behaviour of a multiphase medium carbon steel: Comparison between ferrite/pearlite and tempered microstructures

Fatigue crack growth is the essential process in the total life of components and is unavoidable in most structures and machines. In this study, the effects of cementite particles on the fatigue properties of medium carbon steel were investigated. A quenching and tempering treatment was developed to obtain uniformly distributed cementite particles with dozens of nanometres. To evaluate the fatigue properties, fatigue strength, fatigue crack growth rate and dynamic mechanical behaviour were examined. It was found that the fatigue strength of the tempered steel is much higher than that of air cooling ferrite/pearlite steel because the cementite particles act as barriers and hinder crack propagation during cyclic loading. More importantly, the high sensitivity of the damping peak to prior fatigue may play an important role on the fatigue history of multiphase medium carbon steel.