In order to improve the durability and cost performance of weld overlay superheater tubes used in high efficiency waste-to-energy boilers, a reverse polarity plasma arc welding process was developed. Evaluation of the high-temperature corrosion-resistance was carried out by using a thermal gradient corrosion test method and by a 4000 hour field corrosion test in a high-efficiency waste-to-energy boiler supplying 500°C/9.8MPa steam. From these evaluations, good corrosion-resistance which is equal to conventional weld overlay processes, or more, was confirmed. Especially with a newly developed process, localized corrosion arising in the bonding part of SA178/weld
metal and selective corrosion of the weld metal were less than conventional welding processes due to it's lower dilution and heat input.
Keywords : weld overlay, waste-to-energy plant, superheater tube, alloy 625, alloy 310, corrosion-resistant materials, reverse polarity plasma arc welding, thermal gradient corrosion test, field corrosion test, locarized corrosion, corrosion life evaluation