Mechanism of improving corrosion resistance in heat affected zone of duplex stainless steel by tantalum addition.

The effect of tantalum addition on corrosion resistance in HAZ of duplex stainless steel was investigated by pitting corrosion test and material characterizations (SEM, TEM, APT). The Ta addition improved corrosion resistance of HAZ simulating welding at low heat input and rapid cooling rate since Ta segregated in the Cr nitrides and suppressed formation of Cr-depleted zone. The Ta addition also improved corrosion resistance in HAZ subjected to isothermal aging heat treatment assuming welding at high heat input and low cooling rate because Ta promotes the formation of χ phase and delays the formation of σ phase and Cr-depleted zone. • Ta addition improves corrosion resistance in HAZ of duplex stainless steel. • Ta suppresses Cr-depleted zone associated with Cr nitride formation. • Ta promotes χ phase formation and suppresses Cr-depleted zone associated with σ phase. [ABSTRACT FROM AUTHOR]