There is currently approximately 10% cobalt (Co) in the matrix of tungsten carbide (WC) cermet armor piercing projectiles. The US Department of Health and Human Services has classified cobalt as “reasonably anticipated to be a human carcinogen”. The classification of cobalt as an “anticipated carcinogen” has resulted in subsequent complications (i.e. strict industrial controls) in the production and machining of cobalt‐containing bodies for all applications, not just armor‐piercing cores (e.g. tooling, jewelry, abrasives, etc.), where the inhalation of airborne dust can be hazardous to persons handling or machining these materials. The objective of this topic is to identify non‐hazardous alternative matrix materials for tungsten carbide cermets that will yield materials with the necessary properties for use in armor‐piercing projectiles.
This SERDP Special Study focused on the science needed to achieve success in this area, as well as the environmental impact this topic encompasses.
Tungsten carbide (WC) cermets are among the most successful composite materials yet developed, with a unique combination of high hardness, strength, and fracture toughness. This combination of properties, along with exceptionally high density, provides a superior material for small caliber armor‐piercing projectiles. The current state of the art is ≈10% cobalt (Co) matrix. Cobalt is a critical and strategic material for the US military due to its utilization in tungsten carbide munitions, however, cobalt supply is influenced by economic, environmental, political, and technological factors affecting exploration for and production of copper, nickel, and other metals as well as factors affecting the cobalt industry. Moreover, The United States is predominately import dependent for cobalt. Much of the cobalt supply is derived as a byproduct of copper and nickel mining. Consequently, economic, environmental, political, and technological factors affecting copper and nickel exploration and production may also affect cobalt supply. The demand for cobalt raw materials has increased, due to the emergence of China as a major producer and consumer of refined cobalt, primarily for rechargeable batteries. In 2012, worldwide estimates of the amount of cobalt mined/refined were estimated to be ≈92,000 tons/year.
Through interviews, it became clear that research should focus on two new areas, not previously looked at. These areas include:
- Thermodynamic modeling of new alloys using Thermocalc modeling for focusing on wetting, compaction/consolidation of powders, melting temperature and viscosity properties as well as mechanical properties
- How best to modify ternary alloys
Elimination of cobalt‐containing materials is essential and advantageous from two perspectives, reduction of potential health risks associated with these materials as well as stabilization of the supply chain and cost. Efforts need to be initiated to identify non‐hazardous alternatives to cobalt that will yield materials with the necessary properties for use as armor‐ piercing projectiles. Attention is slowly starting to focus on cobalt‐free compositions for economic, as well as environmental reasons. It is anticipated that the results of this work will also benefit industrial applications because tungsten carbides containing cobalt are also widely used in the commercial sector in cutting tools, coatings, saw blades, and wear‐resistant components in industrial machinery, as well as in sporting goods and surgical equipment.