15Kh1M1F steel fracture during creep in dependence of structure type

15Kh1M1F steel castings after heat treatment comprising two normalizations (the first one at 1030-1050, the second one at 980-1020 deg C) and tempering at 730 deg C are inves-- tigated. The nature of long-term splitting fractire has been studied by means of a light microscope on microsections cut out near the sample fracture as well as on sample fractures by means of an electron microscopy using the technique of microfractography. It is shown that the square of sections of intercrystalline fracture in metal with bainite structure after tests of equal duration is two times larger than in the fracture of metal with ferrite structure. Intercrystalline fracture in metal with bainite structure after 10000 h test is typical for such tests at high temperature that is fracture due to pore formation while for mwetal with ferrite structure these sections of fracture are absent