Shot-peening of steam turbine blades: Residual stresses and their modification by fatigue cycling

摘要: Abstract Power generation in thermal stations typically relies on large steam turbines. The corrosion resistant steel blades used the last stage of a typical low pressure rotor set are approximately 1m long and experience high centrifugal loading during service. They operate wet environment, at 120 °C while rotating 3000 rpm, failure modes either stress cracking or fatigue. retained by fir tree root which is shot-peened to generate compressive residual stresses that resist crack initiation. Finite element (FE) modelling has indicated that, absence shot-peening, above yield induced operation. To date, no systematic information been obtained level shot-peening their relaxation, nor there any guidelines as magnitude necessary ensure integrity turbine over life span least twenty years. At one these failed recent years causing catastrophic severe damage turbinegenerator set. This paper will report results from comprehensive program measurements roots service blades, specimens simulate root, using diffraction data laboratory synchrotron X-ray radiation (SXRD). Shot-peening coverage between 75% 200% was were measured up 5 mm into blades/specimens. Measurements made as-peened condition after applying cyclic representative overspeed proof testing be calibrate FE input fatigue prediction.