Enhancement of mechanical properties and corrosion resistance in laser lap welding joint of zirconium R60702 by forced water-cooling

A comparison was conducted on the microstructure, mechanical properties, and corrosion resistance of the fusion zone (FZ) in Zr R60702 laser lap joints prepared under air-cooled and water-cooled conditions. The results reveal that the upper and lower regions of the FZ in the welded joint consist of dendritic structure and α′ martensite, respectively. When water-cooled forced cooling is applied, α′ martensite emerges in the upper region of the FZ, with a few dendrites exhibiting an isoaxial distribution. Furthermore, the α′ martensite in the lower region becomes noticeably refined. The utilization of water-cooling triggers multiple strengthening mechanisms that, through synergistic interactions, enhance the microhardness, strength, and plasticity of the welded joints. The improved corrosion resistance within the FZ of the welded joint is attributed to the formation of a more stable passivation film.