Study on the corrosion fatigue properties of ultrasonic surface strengthened axle steel

Abstract

Owing to fatigue damage and environmental erosion, locomotive axles are prone to premature failure during service. It is therefore very important to improve the corrosion fatigue properties of axles. In this paper, the fatigue behavior of ultrasonic surface strengthened axle steel under corrosive environment was studied. The surface integrity of ultrasonic strengthened axle steel was characterized by microscopic analysis and hardness test. The fatigue data and fatigue fracture of axle steel under corrosion environment were compared. Also, the mechanism of the corrosion environment on fatigue crack initiation and propagation was analyzed. Results show that serious plastic deformation is generated in the surface of axle steel after ultrasonic strengthening. The grains in surface layer are obviously refined and get coarse gradually as deep into the matrix. The hardness of surface layer is greatly improved as well. The maximum value is located on the outermost surface, about 2 times of the matrix. Under the same fatigue load, the fatigue cycle number for ultrasonic strengthened axle steel is more than that of original sample. This is due to grain refinement, work hardening, and residual compressive stress induced by ultrasonic strengthening, which inhibits fatigue crack initiation in corrosion environment.