COMBINED QUENCHING AND TEMPERING INDUCED PHOSPHORUS SEGREGATION TO GRAIN-BOUNDARIES IN 2.25CR-1MO STEEL

Combined quenching and tempering induced phosphorus segregation to pri or austenite grain boundaries in a 0 . 077 wt-%P doped 2 . 25Cr-1Mo st eel was examined using field emission gun scanning transmission electr on microscopy. the results indicate that combined equilibrium and non- equilibrium phosphorus segregation may play an important part in tempe r embrittlement of the steel caused by direct tempering after quenchin g. Non-equilibrium segregation requires the formation of sufficient qu antities of vacancy-impurity complexes and their migration to gain bou ndaries is of great importance in the segregation. For this reason, th e mechanism for migration of the complexes is discussed in detail. (C) 1996 The Institute of Materials.