The microstructure stability of welded power plant steel components is typically assessed using the precipitate growth kinetics. The long-term exposure of welded structures at high temperatures results in coarsening of precipitates which may lead to the failure of the components. The dilution of base and filler material in the weldment could give rise to detrimental precipitates. The present work proposes an Integrated Computational Materials Engineering (ICME) methodology to identify optimum dilution levels for welded components used during high-temperature aging to obtain best possible lifetime for the component. For this study, the TC-PRISMA® module of ThermoCalc® software was used for precipitation calculations after appropriate benchmarking. Weld dilution study was performed to predict dilution effect influence on Laves phase precipitates in a welded component of CB2 and P92 steels during aging for up to 100,000 h. From the dilution study, it was found that the composition of the weld affects the size and coarsening of the Laves phase precipitate. It was also observed that the size of Laves phase precipitates for all dilution ratios remains within the critical size limit for CB2 steel and it exceeds the critical size limit in P92 steel during aging. Based on the study, an ICME workflow was proposed to determine the optimum dilution ratio for welded power plant steel components used in high-temperature applications for obtaining the best possible lifetime for the component and to reduce the associated cost of experimental trials. © 2021, ASM International.