Weld repair of ferritic welded materials for high temperature application

Abstract

Weld repair of ferritic and austenitic materials, particularly related to high temperature applications, has become increasingly important as the life of high temperature operating plant has been extended to obtain the maximum economic benefit commensurate with rigorous safety requirements. This has led to the development of advanced and innovative repair procedures which rely on the improved understanding that now exists for the control of the microstructures developed in the heat affected zone and the weld metal. This review focuses on the weld repair of ferritic steels and considers the factors that contribute to the damage build up in components requiring repair, especially weldments, and the typical repairs that are required. It considers the basic features of conventional welds and weld repairs, the assessment of their performance, the principles of microstructural control and their application to advanced repair procedures. Finally, it examines the different methods of assessing the performance, the various controlling parameters, summarises the current guidelines and finally considers the future requirements. Wherever possible, use is made of reviews in associated fields.

Microstructural Characterization of the Heat-Affected Zones in Grade 92 Steel Welds: Double-Pass and Multipass Welds

“…The thermal history in the HAZ of a multipass weld is more complicated and the characterization of the weldment needs to include consideration of both the reheated weld metal and reheated HAZ regions. [4,5] Each of the weld thermal cycles exposes a given region in the HAZ to a variable peak temperature and unique heating and cooling rate specific to the distance of the location from the weld source. [6] The microstructure in the HAZ is, in turn, controlled by the thermal history resulting from the welding process.…”

Review Type IV cracking in ferritic power plant steels

“…Methods of weld repair for existing creep damage have been reviewed elsewhere. 9 The focus here is on the newer steels containing between 8 . 5 and 12 wt-% chromium, i.e., candidate materials for future power plant applications.…”

Design of Boiler Welding for Improvement of Lifetime and Cost Control

“…In general, heat generated from latter pass can effect on microstructure of former pass joint. A number of different structures, recrystallization, and grain growth can be generated in the former pass region as reported in the literature [ 12 ]. In this study, granular bainite was presented in the former pass region.…”

“…A boiler rack, a bundle of steam tubes, is usually welded to a header or manifold. Because maintenance of boiler is costly and complicated, many works have emphasized the effect of weld microstructure on boiler lifetime, especially the effect on corrosion behavior, which has a great influence on the boiler lifetime, and the techniques for improvement of the boiler lifetime, e.g., use of inhibitors, control of exposure time and temperature, design of heat treatment, and design of weld repair [ 1 , 7 , 8 , 9 , 10 , 11 , 12 ]. There are three zones of the weld, fusion zone (FZ), heat affected zone (HAZ), and base metal (BM), which have different microstructures leading to different corrosion behavior [ 9 , 13 ].…”