Molybdenum (Mo), with its high chemical stability and resistance to neutron irradiation, has wide application prospects in the nuclear industry; however, the embrittlement of welded Mo joints limits its further application. In this study, the brittleness of the welded joints of Mo alloy was reduced and their strength was enhanced by adding carbon to the fusion zone (FZ) during laser welding. In the FZ of the Mo joints, carbon mainly existed as Mo₂C, and some free C atoms, and MoC and MoO_xC_y phases were also present. The distribution of Mo₂C directly influenced the bonding strength of the grain boundaries. As Mo₂C was dispersedly distributed as particles or discontinuous lines at the grain boundaries of Mo, it improved the resistance of the grain boundaries to the propagation of cracks and thereby increasing their strength. However, the Mo₂C phases distributed in a reticular pattern at the grain boundaries of Mo provided channels that enabled cracks to rapidly propagate, thereby reducing the resistance of the grain boundaries to crack propagation and weakening their strength. The emergence of the MoO_xC_y phase reduced the weakening effect of free oxygen atoms on the strength of grain boundaries of Mo.

钼（Mo）具有很高的化学稳定性和耐中子辐射性，在核工业中具有广阔的应用前景。但是，Mo焊接接头的脆性限制了其进一步的应用。在这项研究中，通过在激光焊接过程中向熔合区（FZ）添加碳，可以降低Mo合金焊接接头的脆性，并提高强度。在Mo接头的FZ中，碳主要以Mo ₂ C的形式存在，并且有一些自由C原子，并且还存在MoC和MoO _x C _y相。Mo ₂ C的分布直接影响晶界的结合强度。作为Mo ₂C以颗粒或不连续线的形式分散分布在Mo的晶界处，它提高了晶界对裂纹扩展的抵抗力，从而提高了其强度。但是，在Mo的晶界处以网状分布的Mo ₂ C相提供了使裂纹快速扩展的通道，从而降低了晶界对裂纹扩展的抵抗性并削弱了其强度。MoO _x C _y相的出现减少了自由氧原子对Mo晶界强度的减弱作用。