EVOLUTION OF SECONDARY PHASES DURING QUENCHING AND TEMPERING 12-PERCENT CR STEEL

Secondary phase evolution in the 12 wt.% Cr steel austenitized at 1100 and 1330 degrees C and subsequently tempered at 750 degrees C was inv estigated. To describe the microstructures and identify the secondary phases, methods of light microscopy and transmission electron microsco py including electron diffraction and microanalysis were used. It was found that oil quenching from 1100 degrees C leads to formation of aut otempered martensite containing intragranular (Fe4Cr)(3)C and MN parti cles. After oil quenching from 1330 degrees C the microstructure consi sts of martensite, delta-ferrite, intragranular MN particles, and M23C 6 particles precipitating at the gamma/delta interfaces. In microstruc tures of tempered states Cr-rich M23C6, Ti-rich MN, and V-rich MC part icles were found. It was shown that quenching temperature and/or appea rance of delta-ferrite in the microstructure do not significantly affe ct the evolution of secondary phases during tempering. (C) 1998 Elsevi er Science S.A. All rights reserved.