Surface Integrity Characteristics and Fatigue Failure Mechanism of Carburized M50NiL Steel

Abstract

The surface integrity of carburized M50NiL steel was studied by optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), microhardness tester and residual stress tester. The fatigue properties of the two specimens were measured by the rotational bending fatigue test, and the fatigue test results were simulated and analyzed. The results show that the rotation bending fatigue of carburized M50NiL steel is originated in the sub-surface in the ideal case without considering the surface processing defects. The surface stress concentration factor produced by general grinding causes the fatigue source to be moved from the surface to the sub-surface. Precise grinding improves the surface quality by optimizing the grinding process, effectively restrains the stress concentration of the working surface, and returns the fatigue source from the surface to the sub-surface. The maximum rotary bending fatigue life can be increased by 30 times and the average is 15 times.

Keywords

• M50NiL steel
• grinding
• surface integrity
• fatigue
• failure mechanism