Alumina ceramic is an indispensable material in modern industry, among which hardness is one of its particularly outstanding characteristics. In this article, we will discuss the hardness of alumina ceramics and help you understand this important characteristic from all aspects.
What Is The Hardness of Alumina Ceramics?
Hardness is an important indicator of a material’s ability to resist local deformation or scratches. In ceramic materials, high hardness can affect the product’s service life and wear resistance.
The hardness of alumina is very outstanding among many ceramic materials and it is a superhard material second only to diamond.
- Mohs hardness：9
- Vickers hardness：15~20 GPa
The Reason for The High Hardness of Alumina Ceramics
The high hardness of alumina ceramics is determined by various factors：
Crystal Structure
Alumina ceramics are a corundum structure with a very precise atomic arrangement and very high bonding strength, which is one of the factors for its high hardness.
Chemical Bond Strength
In the microstructure of alumina, ionic bonds and covalent bonds are combined, which makes its internal structure extremely stable and difficult to destroy.
Material Purity
Purity is also a major factor affecting the hardness of alumina ceramics. High purity can reduce the interference of impurities on the crystal lattice. Therefore, high-purity alumina (such as 99% and above) has stronger hardness.
Alumina’s Use in Hardness
Alumina has excellent performance in industrial wear-resistant parts due to its high hardness, and compared with steel, the wear resistance of alumina ceramics can be improved several times. Alumina can be made into various high-wear-resistant products such as grinding wheels, grinding sand, bearings, high-temperature furnace linings, engine parts, etc.
- Frosted
- Mechanical bearings
- High temperature furnace lining
- Engine components
- Cutting tools
- Pump valve parts
- Substrate
- Artificial joint implants
Test Method for Hardness of Alumina Ceramics
Mohs Hardness Test
The Mohs hardness test is a method of evaluating the hardness of a material by observing a scratch on its surface. Alumina ceramic has a Mohs hardness of 9, which is slightly lower than diamond’s 10, but is enough to easily scratch glass and other softer materials.
Vickers Hardness Testing
The Vickers hardness test uses a diamond pyramid to press into the surface of the material, measuring its indentation area to calculate the hardness value. The Vickers hardness of alumina ceramics is 15~20 GPa, which shows that alumina has very strong compressive resistance.
How to Improve The Hardness of Alumina Ceramics?
1.Using higher purity alumina ceramics, the impurities are reduced and the hardness of the alumina ceramics will be higher
2.Optimize the sintering process, such as using hot pressing or microwave sintering to improve density
3.Adding modifiers, such as adding an appropriate amount of zirconium oxide and other materials, can further enhance the hardness and toughness of alumina
Conclusion
Alumina ceramics play a key role in industry with their excellent hardness performance. High hardness can not only extend the service life of the product, but also improve work efficiency. Thank you for reading this article.
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FAQ
What is the hardness of alumina ceramics?
The Mohs hardness of alumina is 9 and the Vickers hardness is 15~20 GPa.
Is alumina ceramic harder than steel?
Yes, alumina ceramics are much harder than most steels, but you need to be aware that alumina ceramics are less tough.
In what scenarios are high-hardness alumina ceramics mainly used?
The high hardness of alumina is very suitable for various wear-resistant parts, high-temperature parts and medical equipment.