Crack-Free Welding of a Co-Base Superalloy with High γ' Precipitate Fraction

Abstract

Laser cladding of superalloys provides an attractive and cost-efficient technique for near-net shape manufacturing, remanufacturing, or individualized repair of components. While the weldability of γ' hardened Ni-base superalloys is limited, Co-base superalloys should have a lower susceptibility for cracking during welding due to a lower γ' solvus temperature and less segregation than Ni-base superalloys. The weldability of the Co-base superalloy CoWAlloy2Mod and the resulting mechanical properties at 950 °C are investigated. In the as-welded condition of CoWAlloy2Mod, a fine dendritic microstructure without forming cracks and limited porosity is found. After a three-step heat treatment, recrystallized, equiaxed grains and a high γ' volume fraction are obtained leading to a very good strength. CoWAlloy2Mod shows a significantly higher strength and creep strength than the conventional weld filler Co-alloy PWA795.