Study on the microstructure and properties of rail cladding layer after laser quenching

Abstract

The U71Mn rail surface processed by laser cladding suffers from large rough area and grain size at the top of cladding layer as well as residual tensile stress in the cladding layer. This paper proposes to remanufacture rail surface by combining laser cladding with laser quenching. The experiment results show that the quenched cladding layer was transformed from dendritic to equiaxed crystals at a specific quenching depth, with refine grains. Laser quenching results in dense martensite structure on the surface of the cladding layer. The hardness of the cladding layer after quenching is about 895 HV0.2, 18 % higher than that before quenching. The wear rate after quenching is 0.713 μm3/(N∙μm), with a decline of 22.3 % compared with that before quenching 0.918 μm3/(N∙μm), indicating that wear resistance is improved after laser quenching. In addition, the cladding layer after quenching exhibits stronger corrosion resistance than that before quenching, and internally it is transformed from tensile stress to compressive stress, with a maximum residual compressive stress of about −486 MPa, which endows the rail with stronger fatigue performance and longer service life.