Abstract
Cast superaustenitic stainless steels with ∼6 wt-%Mo are used in applications requiring good corrosion resistance. However, the weld corrosion resistance is reduced due to Mo microsegregation. Ni based filler metals with higher Mo concentrations are typically used to compensate for this problem. The weld corrosion resistance and microstructural evolution are controlled by the weld composition, which is a function of the welding parameters. This article describes the effect of weld composition on the microstructure and corrosion behaviour of welds on cast alloy CN3MN using IN686 filler metal. The amount of interdendritic σ phase was independent of dilution due to offsetting changes to the nominal composition, eutectic composition and distribution coefficient. The weld corrosion resistance improved significantly with decreasing dilution due to higher concentrations of Mo in the fusion zone. A post-weld heat treatment of 1150°C for 1 h restored the corrosion resistance, which is attributed to weld homogenisation.
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