The alloyed martensitic P91 steel was chosen for the analysis
since it is quite often used for the manufacturing of steam superheaters,
i.e. the most thermally-loaded heat transfer surfaces in the
boilers. The chemical composition and mechanical properties of the
steel are shown in Tables 1 and 2, respectively (in Table 2 Rp0,2 is the
tensile yield stress, Rm is the tensile strength, and Amin is the
elongation).
The steel tube samples were exposed to thermal treatment in
one of Polish large-scale (over 400 MW) bituminous coal-fired CFB
boilers. The particle size of the designed fuel was