Extended Analysis Of A Cutting Tool Material Microstructure By DualEELS Spectrum Imaging

Abstract:

This paper offers an insight into the microstructural evolution of a cubic Boron Nitride based cutting tool material (50% polycrystalline cubic boron nitride in a TiCN matrix ) by using advanced analytical transmission electron microscopy methods.Owing to newly developed high resolution spectrometers and detectors, electron energy loss- spectra acquired in scanning TEM mode as a spectrum image (EELS SI), offers the possibility to find answers to increasingly thorny questions. This method produces full data sets, containing the complete spectroscopic signature with both high spatial and energy resolution. By using more sophisticated off-line processing, subnanometer localized information which may promote the understanding of the nucleation and/or elemental enrichment of different phases, can be extracted. EELS spectrum images, acquired in DualEELS mode, by using the prototype of a Gatan Quantum spectrometer mounted on a monochromated Tecnai F20 microscope, have been processed from a commercial polycrystalline cubic Boron Nitride (PCBN) sample provided by Chalmers Technical University and Sandvik Tooling, Sweden.This analytical method combined with a multiple linear least square fitting procedure enables the calculation of elemental maps containing areal and/or volumetric densities of each element bounded in different phases. Therefore, EELS fine structure and absolute edge energy information have been involved to unambiguously chart the aluminum, boron, carbon, nitrogen, titan and oxygen bounded in c-BN, TiC0.7N0.3, TiC0.5N0.5 , TiB2, Al2O3 and oxidized AlN. Moreover the oxygen present as surface oxidation of TiCN phases has been evaluated.

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