Development and Application of T91 Cold Weld Repair Techniques

Abstract

Abstract The application of cold weld repair techniques in the power industry has been well documented. This type of repair is only considered when a conventional repair (involving post-weld heat treatment) is impracticable or the penalties of time and cost for conventional repair are sufficiently high. A typical cold weld repair in the UK has involved low alloy ferritic steel (½Cr½Mo¼V, 2¼Cr1Mo) components welded with nickel based SMAW consumables or ferritic FCAW consumables. Modified 9Cr steel components have been used in UK power plant since the late 1980’s for a number of applications, such as superheater outlet headers, reheat drums and main steam pipework. The problems associated with this material have also been well documented, particularly premature type IV cracking of welds on creep weakened modified 9Cr steel. RWE Generation UK have developed modified 9Cr cold weld repairs on headers, pipework and tubes. These repairs have been underwritten with extensive testing. This paper will describe the work performed on developing T91 cold weld repairs and where they have been applied on power plant.