Effect of deep rolling parameters on surface integrity of LZ50 axles

Abstract

Deep rolling is a surface treatment method by which a hydraulically controlled ball produces a specific pressure on material surface, causing plastic deformation and introducing compressive residual stresses. In this paper, LZ50 steel which is often used as high speed train axle is treated by deep rolling. Surface morphology was observed, and roughness, microhardness and residual stress were measured. Effects of deep rolling parameters (pressure, feed speed, speed, number of runs) on the surface integrity of LZ50 axles were studied systematically. The results show that the surface roughness decreases obviously after deep rolling compared with the original surface. The feed speed has greater influence than other parameters on surface roughness. The minimum roughness (Ra) can decrease to 0.14 [Formula: see text]m. The surface layer of LZ50 deforms in different degrees. Meanwhile, the surface stress state of LZ50 changes from tensile stress to compressive stress after deep rolling. The maximum residual compressive stress is 862 MPa. The main influence factor is pressure. However, for LZ50 axle, the surface hardness does not change significantly after deep rolling.