Fracture lifetime of hydrogen-charged AISI 4130 alloy steel under intermittent sustained overloads

The fracture lifetime of a hydrogen-charged AISI 4130 alloy steel under various intermittent sustained overloads was investigated. Overload ratios of 1.4, 1.7, and 2.0 were used to establish five types of intermittent sustained overloads. The magnitude of fracture lifetime was rationalized using the mechanisms of residual compressive stresses, crack closure, dislocation shielding, and hydrogen damage. The fracture lifetime prolonged with increasing the overload ratio and decreasing the hold time and time period. The sustained overloads with the ratio of 2.0, 0.5-h time period, and 0.1-h hold time maximized the fracture lifetime, about 90-fold the lifetime under the overload-free conditions.