The Effects of Carburization on the Fatigue Crack Growth Behaviors of Local Surface Cracks in Cylindrical Bars

In this study, a series of fatigue tests were conducted on C45 steel specimens with local surface cracks. The effects of carburizing treatment with different case depths were discussed under cyclic tensile and torsional loading. Moreover, the surface crack extension paths and crack propagation rates were discussed. In addition, the effects of additional static torsion under cyclic tensile loading and additional static tension under cyclic torsional loading were analyzed, and comparisons were made between the results of the carburized materials and those of the uncarburized materials. Some conclusions show that carburization can effectively retard crack extension and improve fatigue life. However, the improvement provided by the case depth on the fatigue life is limited to a certain range, and extensive case depths might decrease the fatigue strengths of materials. For the studied material, carburization had a more direct influence on the crack growth under cyclic tensile loading than cyclic torsional loading.