Complete TEM investigation of a nitrided layer for a Cr alloy steel

Abstract

Un-nitrided material is investigated by TEM in order to identify the different types of precipitates and to determine their respective volume fraction. M23C5 and M4C3 carbides arc reported. Experimental results are confirmed by thermodynamical calculations. The same material is nitrided in industrial conditions and also investigated by TEM. Crystallographic structures and chemical compositions are determined by Selected Area Electron Diffraction (SAED), Energy Dispersive Spectroscopy (EDS) and Electron Energy Loss Spcctroscopy (EELS). V-rich carbonitrides, incoherent globular CrN nitrides and semi-coherent CrN nitrides are reported. In both cases, CrN precipitates have the Baker-Nutting orientation relationship with respect to the ferritic matrix. Their size distributions as a function of depth are studied. © EDP Sciences 1998.