Hardmetal
A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".
Deadline for manuscript submissions: closed (15 December 2020) | Viewed by 8966
Special Issue Editors
Interests: novel synthesis; magnetic materials; bulk metal glass; high entropy alloys; superconductors
Interests: computational materials design; integrated computational materials engineering; cemented carbides; alternative binders; microstructures; properties
Interests: Phase transformations in metallic alloys and hardmetals
Special Issue Information
Dear Colleagues,
‘Hardmetal’ has a very particular meaning – it is not about a hard metal in general - it means a composite of (typically) tungsten-carbide grains in a cobalt matrix, the so called ‘binder’ (CoWC). It is used as inserts in all sorts of tools in a wide variety of applications for metal cutting and rock drilling and wherever high wear resistance is needed. ‘Hardmetal’ as such represents a huge market of 10s of thousands of tons pa at present.
Historically it has been around for ca 100ys, and it is industrially prepared by a sintering process. Powders/grains of the hard constituent is mixed with the binder, compressed and sintered at about 1500C. Obviously this concept has experienced substantial development over the years. E.g. the grain size has decreased from several micrometers at the beginning to being in the nanometer range at present. However, these improvements are still rather incremental, and today’s product is not dramatically different from the earlier. Moreover, the cobalt content is now considered becoming increasingly problematic. Cobalt is relatively expensive and has recently become suspect of being carcinogenic. Also, the mining of cobalt in areas like Congo, has made it a ‘conflict mineral’. Thus, there is a definite strive to replace Co with ‘friendlier’ alternatives.
Therefore, we invite researchers in the field of metallurgy as well as from novel preparation techniques like additive manufacturing to contribute to the effort of replacing cobalt and possibly also replace WC with alternatives. Efforts in this direction have shown that even a ‘simple’ FeNi alloy might be a replacement candidate to the binder.
In hindsight it appears that this very combination of the extremely hard WC phase with the particular binder – cobalt – is quite fortuitous. Not only gives cobalt the right amount of plasticity to accommodate slight deformation, but it has also given the composite a very convenient way for quality control by magnetic measurements well suitable for production. Saturation magnetization is directly related to the Co content, and the coercivity is a well understood function of grain size.
Despite this, we are confident that a serious effort, both theoretical and experimental, will eventually lead to a better Hardmetal.
Dr. Ström Valter
Dr. Joakim Odqvist
Dr. David Linder
Guest Editor
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Keywords
- High Entropy Alloys
- Characterization of the grain-binder interface
- Thermodynamic modeling
- Preparation from a uniform precursor
- Wear – models and assessment
- Increased temperature of operation
- Additive Manufacturing
- Spark Plasma Synthesis
