TIG Welding Crack Sensibility Analysis of Co-Based Superalloys

The microstructure of alloy phases and hot crack propagation under TIG (tungsten inert gas) welding of Co-based superalloys are investigated. The μ-phase, β-phase and carbides are grown in the superalloy, and the μ-phase is mainly precipitated. The microhardness of the μ phase is higher than the β phase and the matrix. During TIG welding, the arc crater cracks in the molten pool are all intergranular. The equiaxed crystals are existed in the fusion zone, and the dendrites are appeared in the heat affected zone. The microcracks in the heat-affected zone and closed to the base metal are preferentially initiated in the region of the μ phase, and continuously extend to the matrix along the growth direction of the μ phase.