The present invention is a composite welding wire for fusion welding of components manufactured of superalloys. The composite weld wire includes a surface layer applied to the core wire in a green condition and bonded to the core wire. The surface layer includes alloying elements selected from among B and Si, the total bulk content of B and Si representing 0.5 to 4.0 wt. % of the composite welding wire. The boron and silicon alloying elements reduce the melting temperature and increase the solidification range of the weld pool, minimizing the incidence of weld cracking compared to welding without the coating. The green condition surface layer is comprised of more than 80 wt. % of the bulk content of the composite welding wire selected from the combination of B and Si.