Abstract
Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures.
Highlights
Interfaces and grain boundaries in metal-ceramic composites, WC-Co cemented carbides, play an important role with respect to obtaining high mechanical and performance properties of such materials
This phenomenon almost does not occur in the model alloy with the medium-low carbon content and does not occur in the model alloy with the high carbon content
The formation of Co nanoparticles in the binder model alloy with the medium-low carbon content near the WC/Co interface was established for the first time
Summary
Interfaces and grain boundaries in metal-ceramic composites, WC-Co cemented carbides, play an important role with respect to obtaining high mechanical and performance properties of such materials. There is almost no information in the literature on WC-Co interfaces in WC-Co materials that are not containing grain growth inhibitors at an atomic level by use of high-resolution transmission electron microscopy (HRTEM) studies. Such studies are complicated due to difficulties with respect to finding in transmission electron microscopy (TEM) WC-Co interfaces with both WC and Co grains simultaneously in a zone axis orientation. The interaction between Co-based binders and WC grains in WC-Co cemented carbides on the initial stages of liquid-phase sintering plays an important role with respect to obtaining cemented carbides with proper microstructures and properties. There is no information on interfaces between tungsten carbide grains and Co-based binders having various carbon contents when liquid-phase sintering is interrupted in several seconds after the liquid phase formation
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