The properties and application limits for thin-walled and thick-walled components of heat-resistant steels NF616 and P92 are presented. The study is in view of improving the efficiency and reducing the carbon dioxide emissions of coal-fired power plants by increasing the steam parameters temperature and pressure. The study is focused on the creep rupture strength tests carried out at the Dresden Materials Engineering Department of Siempelkamp Pruef- und Gutachter-Gesselschaft mbH, where the base metal as specimens from similar welds were tested.