boron carbide hardness？
Boron carbide (B₄C) is one of the hardest known materials, with hardness values as follows:
1. Mohs Hardness
- Mohs hardness: 9.5
- It is only softer than diamond and cubic boron nitride (cBN), making it the third-hardest material on the Mohs scale.
2. Vickers Hardness (HV)
- Vickers hardness: 30–40 GPa
- Equivalent to 3,000–4,000 kgf/mm²
- This is the most common engineering hardness scale for superhard ceramics.
3. Knoop Hardness
- Knoop hardness: 2,900–3,580 kgf/mm² (under 100 g load)
Key Notes
- It is often called “black diamond” due to its extreme hardness and black appearance.
- Its hardness comes from a strong covalent network structure of boron icosahedra linked by carbon chains.
- It is widely used in armor, abrasives, nozzles, and nuclear applications because of its high hardness, low density (~2.52 g/cm³), and chemical inertness.