Narrow gap laser welding (NGLW) of structural steels—a technological review and future research recommendations

Advanced welding processes for structural materials are gaining increasing importance for strategic applications in nuclear, aerospace, automobile, and defence sectors. These processes have been designed keeping in view the criterion of minimal stress generation, microstructure retentivity, and process reproducibility. Narrow gap laser welding (NGLW) is one such advanced welding technique that has been developed in the past decade owing to its fabricate-ability of thick-section steels at high welding speeds. Of the many advantages, several characteristics of the process outperform the traditional arc welding processes as well as single-pass autogenous laser welding, including process flexibility, increased welding productivity, excellent weld properties, and the potential for automation. This paper provides a state-of-the-art technological review on the NGLW process primarily for structural steels covering several topics including the effect of process parameters, structure-property relationship, and induced defects and residual stresses of NGLWed joints. A list of future research recommendations based on several research gaps is also reported in this article.