Due to a unique combination of elevated-temperature strength and corrosion resistance, Alloy 740H is a leading candidate for the construction of Advanced Ultra Supercritical coal-fired power plants.To date, virtually no information regarding the solidification behavior of this alloy is available.In this investigation, the weld metal of Alloy 740H and candidate filler metals Haynes 282 and Nimonic 263 diluted by 740H were studied.Computational modeling was used to determine solidification temperature ranges and partition coefficients of these combinations. Small samples of Alloy 740H and mixtures of 740H with filler metals 282 and 263 were cast into small buttons which were used to collect solidification temperature range data. Actual gas tungsten arc welds on 740H plate were compared to the solidification data and computational modeling results. Characterization of these welds after heat treatment revealed γ' free zones which were previously thought to exist only after creep testing. The effect of postweld heat treatment on the microstructure and properties of 740H weld metal was also investigated.

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Due to a unique combination of elevated-temperature strength and corrosion resistance, Alloy 740H is a leading candidate for the construction of Advanced Ultra Supercritical coal-fired power plants.To date, virtually no information regarding the solidification behavior of this alloy is available.In this investigation, the weld metal of Alloy 740H and candidate filler metals Haynes 282 and Nimonic 263 diluted by 740H were studied.Computational modeling was used to determine solidification temperature ranges and partition coefficients of these combinations. Small samples of Alloy 740H and mixtures of 740H with filler metals 282 and 263 were cast into small buttons which were used to collect solidification temperature range data. Actual gas tungsten arc welds on 740H plate were compared to the solidification data and computational modeling results. Characterization of these welds after heat treatment revealed γ' free zones which were previously thought to exist only after creep testing. The effect of postweld heat treatment on the microstructure and properties of 740H weld metal was also investigated.

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