Identification of precipitate phases in CLAM steel

Abstract

Precipitate phases in a reduced activation ferritic/martensitic steel CLAM (HEAT-0912) were observed and analyzed using transmission electron microscopy and energy dispersive spectroscopy. The steel samples were normalized at 980 °C for 30 min and then tempered at 760 °C for 90 min followed by an air cooling. Through the selected-area electron diffraction pattern analyses and energy dispersive X-ray data, eight kinds of precipitate phases were identified to be Ta-rich MX carbonitride with a f.c.c. crystal structure, Ta-rich M3X2 carbonitride with a base-centered monoclinic crystal structure, Ta-rich MSi2 phase with a hexagonal structure, V-rich MX carbonitride with a f.c.c. crystal structure, V-rich M2C carbide with an orthorhombic-simple crystal structure, Cr-rich M23C6 carbide with a f.c.c. structure, Cr-Ta-rich M7C3 carbide with an orthorhombic-simple crystal structure, Cr-rich M6C carbide with a f.c.c. structure, respectively. There appear to have no previous reports of the Ta-rich MSi2, Ta-rich M3X2, V-rich M2C and Cr-rich M6C phases identified in reduced activation ferritic/martensitic steels.