What happens when you combine ceramics and metals? You get a cermet. These composite materials harness the best qualities of both: the high hardness and chemical resistance of ceramics, plus the strength and fracture toughness of metals.
Because of their unique properties, cermets are used everywhere, from high-speed cutting tools to medical implants and even solar energy technology.
In this article, we’ll cover the composition of cermets, how they’re made, and some of the most interesting and useful applications.
Composition and properties of cermets
Cermets are made up of ceramic and metallic materials, which gives them a range of useful properties.
Common cermet compositions
- Tungsten carbide-cobalt (WC-Co): This cermet is often used to make cutting tools. The cobalt content usually ranges from 5% to 10%.
- Titanium carbonitride (TiCN) based cermets: These cermets often use nickel or cobalt as a binder, along with additives such as Mo2C or WC. The ratio of titanium carbide to titanium nitride in Ti(C,N) solid solution is often 50/50 or 70/30.
- Aluminum oxide-platinum (CerMet): This biocompatible material is sometimes used for medical feedthroughs.
Key properties and advantages
- Enhanced strength and fracture toughness: The metal component makes the ceramic less brittle.
- High hardness and wear resistance: The ceramic component contributes to overall durability.
- Chemical resistance: The ceramic also provides corrosion protection.
- Bio-compatibility: CerMet is biocompatible, so it can be used in medical applications.
How are cermets manufactured?
Cermets can be manufactured using a variety of techniques, some of which are well-established and some of which are relatively new.
Traditional methods
- Metal infiltration. In this process, molten metal is drawn into a pre-formed porous ceramic material.
- Sputter deposition. This is often used to create nanostructured coatings, including those used in solar energy applications.
Advanced methods
- Binder-jetting. This is used in the creation of cermets containing titanium carbonitride (TiCN).
- Layered manufacturing. This patented process helps ensure that CerMet feedthroughs are hermetically sealed. Hermeticity levels can reach ≤1,0×10^(-9) mbar.l/s.
- In-direct laser sintering. This is used in the fabrication of experimental reactors.
What are cermets used for?
Cermets’ high hardness, temperature resistance, and wear resistance make them useful in a surprising number of applications.
- Cutting tools and wear parts. Cermets made of tungsten carbide and cobalt (WC-Co cermets) are commonly used in cutting tools.
- Solar energy. Cermets such as gold-magnesium oxide (Au-MgO), chromium-chromium oxide (Cr-Cr2O3), nickel-aluminum oxide (Ni-Al2O3), and molybdenum-aluminum oxide (Mo-Al2O3) are used to absorb solar radiation in solar collectors. Researchers choose the materials, film thickness, and nanoparticle properties to optimize performance, and cermets are “generally considered the best for practical collectors.”
- Medical devices. A cermet of aluminum oxide and platinum allows for smaller, more reliable super-miniaturized feedthroughs for neurostimulation devices. These cermets allow for higher channel counts (as many as 800 channels per square centimeter) and can reduce pitch by more than 50% compared to traditional technology.
- Nuclear technology. Cermet target improvements are being considered for irradiation cycles in the production of plutonium-238.
- Gas-solid heat transfer. Cermets are used in experimental reactors for studying gas-solid heat transfer.
Final Thoughts
Cermets are unusual materials, and their special combinations of properties means they can be used in many different ways. They’re strong, hard, and able to handle high temperatures, which makes them ideal for all sorts of applications.
Researchers are constantly working on ways to make cermets even better by adjusting their composition, how they’re made, and their structure. Because cermets are so adaptable and versatile, they will continue to be important in many industries for years to come.