Properties and Characteristics of Alloy 625 Overlay Tubing for Recovery Boiler Applications, 1998 Engineering Conference Proceedings

A unique alloy 625 overlay tubing produced by a proprietary tube overlay welding process is described. The attributes of this proprietary 625 overlay tubing are briefly described with particular reference to applications in recovery boilers. Extensive evaluation of an alloy 625 overlay tube with SA 210 Al steel substrate was performed to generate the mechanical properties of the overlay tube and to characterize the microstructures of both the overlay and the substrate steel. Effects of the normalizing treatment at 1650 F (900 C) on the microstructures of the overlaid tube were also studied. The metallurgical evaluation showed that this unique overlay tubing exhibits many attributes, thus making it a very attractive material for solving the current type 304L composite floor tube cracking problems. Initial experiences and performances of these proprietary 625 overlay tubes as recovery boiler floor tubes and smelt openings are extremely encouraging.