For many years, low alloy CrMo(V) creep-resistant steels are applied for parts in the construction of energy and chemical structural units working under creep conditions (temperature about 550 °C and pressure about 15 MPa). These steels most often include creep-resistant steel 13CrMo4-4 (ČSN 15 121), 14MoV6-3 (ČSN 15 128), 10CrMo9-10 (ČSN 15 128). The main problem of steam pipe-lines made of these creep-resistant steels is a residual lifetime, because these parts are at presence in most Czech power plants at the end of their designed lifetime (2,5 . 105 hours).This article deals with a lifetime assessment of one steam piping bend made of ČSN steel 15 128 (14MoV6-3) which was operated in conditions of creep damage in Czech fossil fuel power plant until its creep deformation obtained a limit of 1 percent. The overall condition of the bend was assessed using replica and cross section metallography including electron microscopy and by evaluation of mechanical properties in as-received state and after additional laboratory ageing at 600 °C for up to 5 000 hours in air conditions. As the final result, the residual lifetime by using mathematical approaches and standards was estimated.Keywords: low alloy creep-resistant steels, creep, life assessment of steam pipe-lines, microstructure rating charts, laboratory ageing
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