Authors:
Zheng-yang Li
Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China and Key Laboratory for Advanced Manufacturing by Materials Processing Technology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China

Hai-yan Zhao
Yu Gu
Min-lin Zhong
Bin Zhang
Hong-jun Zhang
Wen-jin Liu
Key Laboratory for Advanced Manufacturing by Materials Processing Technology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People's Republic of China

Zhi-yuan Ren
Ming-jiang Yang
Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China

Hua-qiang Lin
National Engineering Laboratory for System Integration of High-speed Train (South), CSR Qingdao Sifang Co., Ltd., Qingdao, Shandong 266111, People's Republic of China

Due to a limited dimension of the focused laser beam, multiple passes are required to treat large surface areas, which results in overlapping of laser tracks. This process increases the cracking susceptibility and is a major barrier for the wide application of the laser treatment. To avoid the formation of cracks in multiple overlapping laser tracks, a novel technique referred to as the laser dispersed alloying (LDA) has been developed. The technique consists of creating a dispersed pattern of laser alloying on the surface to be processed. This treatment enhances the fatigue resistance of the surface layer. In the present study, the microstructure, the residual stress, and the fatigue crack growth rate (FCGR) for the ductile cast iron surface formed with the LDA technique were investigated. It was found that the fatigue resistance of the ductile cast iron is markedly increased after the LDA process, due to the compressive stresses and the fine dendritic structure formed in the laser alloying zone, the excellent bond strength between the laser alloying zone and the substrate, and the martensite shell surrounding graphite nodule in the heat affected zone near the boundary of the laser alloying zone.