Electron Backscatter Diffraction (EBSD)

EBSD patterns and OIM orientation map collected from a Tungsten filament used in scanning electron microscopy.

EDAX Periodic Table of Elements - Tungsten

EDAX Periodic Table of Elements - Tungsten

EDAX Periodic Table of Elements - Tungsten Light Bulb Filament

EBSD is an ideal characterization tool for measuring the grain size of crystalline materials, particularly when the Tungsten-Carbide (WC) grain size approaches the resolution limits of optical microscopy. By indexing the orientation of grains on the sample surface, engineers are able to measure not only grain orientation but also size, shape and distribution and to determine materials phases.

EBSD grain map of a Tungsten Carbide material
EBSD grain map showing grain structures in a WC material where individual grains highlight size and morphology

Grain size distribution of a Tungsten Carbide material
Corresponding grain size distribution resulting from the grain map to the left

Energy Dispersive Spectroscopy (EDS)

Tungsten Carbide (WC) is a ceramic material used in many industrial applications and is well know for its abrasion resistance and ability to withstand high temperatures. One standard application is for cutting tools, where the WC is typically cemented together with a binder material, usually metal such as Cobalt (Co). The metal forms a ductile matrix phase which counters the brittle nature of the WC grains, raising the toughness and durability of the tool.

Elemental map of a Tungsten Carbide material
Elemental map of W (green), Co (blue) and C (red).

Elemental map of Carbon in a Tungsten Carbide material
Standard C elemental map.

Map of Carbon from Tungsten Carbide phase only
Map of C from WC phase only.

EDS elemental mapping is sufficient to examine the distribution of Co in the microstructure but C is much more difficult because of its association with W in WC and its existence as elemental C. Standard elemental mapping cannot distinguish between C in different phases. EDAX’s Smart Phase Mapping has the unique ability to be able to look at C distribution as it relates to each phase; whereas, competitive systems provide only overall distribution. Engineers gain invaluable insight from this accurate depiction of the microstructure.

Wavelength Dispersive Spectrometry (WDS)

The thermal shock properties of WC tools are controlled by the varying percentage of the binder phase and with specific binder additives to modify transport properties of the final composition. While EDS is often sufficient to analyze the amount of binder present, the additives are often present in minute amounts, requiring the trace analysis capabilities of WDS. The image below shows two WDS spectra from a binder phase, one with trace Fe additive (red) and one without (green). The increased sensitivity of WDS, paired with the resolution necessary to resolve crowded low energy X-ray lines, allows engineers to make very small changes to binder composition and design the thermal properties of the tool to match the application.

WDS spectra from 2 different regions of binder phase of a Tungsten Carbide material
WDS Spectra from two different regions in the binder phase.