Abstract
This paper presents changes in mechanical properties and microstructure of the material of components of a power station boiler made of X10CrWMoVNb9-2 (P92) steel after long-term thermal ageing. Mechanical properties and microstructure were examined on material in initial heat treatment condition and after long-term thermal ageing up to 100,000 h at 600 and 650 °C. The microstructure was observed using a scanning and transmission electron microscope. The examinations of steel microstructure and mechanical properties in initial heat treatment condition have confirmed that the requirements for this steel are met. Long-term thermal ageing at a temperature similar to the operating one as well as mechanical properties and microstructure examinations have enabled the effect of the long-term impact of temperature on properties and microstructure of P92 steel to be evaluated. The presented method can be used for evaluation and qualification of microstructural changes in power station boiler components operating under creep conditions.

Key words
P92 steel, microstructure, mechanical properties, long-term thermal ageing

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