Time-temperature-precipitation and property diagrams for super duplex stainless steel weld metals

Super duplex stainless steel (SDSS) weld metal microstructures, covering the complete temperature range from ambient to liquidus, were produced by arc heat treatment for 1 minute and 10 minutes. Temperature modelling and thermodynamic calculations complemented microstructural studies, hardness mapping and sensitization testing. After 1 minute, intermetallics such as sigma and chi phase had precipitated, resulting in moderate sensitization at 720-840°C. After 10 minutes, larger amounts of intermetallics resulted in hardness up to 400 HV0.5 and more severe sensitization at 580-920°C. Coarse and fine secondary austenite precipitated at high and low temperatures, respectively: The finer secondary austenite was more detrimental to corrosion resistance due to its lower content of Cr, Mo and N as predicted by thermodynamic calculations. Increased hardness and etching response suggest that 475°C embrittlement had occurred after 10 minutes. Results are summarized as time-temperature-precipitation and property diagrams for hardness and sensitization.