Microanalytical characterization of a powder metallurgical ledeburitic tool steel by transmission electron microscopy

The microanalytical investigation of a new powder metallurgic tool steel was performed with an analytical transmission electron microscope. The chemical composition of the matrix and the precipitates were determined with the help of X-ray spectrometry (EDX) and electron energy loss spectrometry (EELS). The crystallographic parameters of the precipitates were determined by means of convergent beam electron diffraction (CBED). Two different types of precipitates could be prooved: small spherical precipitates with grain sizes of 0.3-1μm of type MX and larger precipitates with grain sizes of 1-4μm of type M7X3. The EDX and EELS microanalyses for the carbide MX resulted in a composition of 56.5 at.%V, 8.5 at.%Cr, 30 at.%C and 5 at.%N. For the carbide M7X3 the composition was 11at.%V, 32at.%Cr, 29at.%Fe and 28 at.%C. The lattice constant of the cubic vanadium carbonitride was determined as 0.4122 nm. The lattice constants of the hexagonal M7X3 are a0 = 0.69 nm and c0 = 0.47 nm. (Author)