The influence of the structure of casting high-temperature nickel alloys on their crack resistance at welding has been studied. It has been shown that crack formation in the weld-adjacent zone is promoted by the presence of lamellar precipitates of the σ-phase, large colonies and eutectic films of the γ΄-phase, carbides, and topologically close-packed phases on the grain boundaries, as well as the heterogeneity of distribution of the liquating elements. Homogenization heat treatment of the base metal before welding provides the maximum level of crack resistance and heat resistance of the joints. It is established that the ratio of Тc.d.γ΄, Teut. and Ts has a great influence on the formation of a ductile metal layer in the weld-adjacent zone of the cast workpiece, which improves its crack resistance at surfacing and welding. To prevent crack formation during welding of alloys with Teut. (Ts) < Тc.d.γ΄, it is necessary to apply new filler alloys with a zirconium-containing eutectic phase.
Thermodynamic analysis of the topologically close packed σ phase in the Co Cr system