Working within metallurgical limitations in the successful repair welding of power-plant components

CIM Bulletin, Vol. 74, No. 831, 1981

W.H.S. LAWSON and D. MILLS, Ontario Hydro Research Division, Toronto, Ontario

The need to make repairs is seldom a major consideration in the design, fabrication and installation of major components of electrical generation plants. Repair welding, however, is a fact of life in the electrical generation industry, for restoration of degradation in service, from cavitation of hydraulic turbine runners, to corrosion and fatigue damage in pressure vessels. In making weld repairs to carbon and low-alloy steels, the largest source of trouble is hydrogen embrittlement and related post-weld cracking. Various strategies have been developed to control problems from this source, including post-weld heat-treatment, the use of nickel-base alloy filler metals and the temper bead welding technique. Each of these basic strategies is being applied as circumstances require; each strategy must, however, be implemented in a manner that reconciles weld-ment structure and hardness, degree of restraint and service environment with the consequences of unsatisfactory performance of the repaired component.
Keywords: Technology, Metallurgical sciences, Welding, Repair welding, Power plants, Hardness