The hardness of white fused aluminum oxide

The hardness of white fused aluminum oxide is 9.0 on the Mohs scale.  And Knoop hardness of white fused aluminum oxide is 20500N/MM2.  It is harder than most metal, stainless steel, and alloy parts. Therefore, it can grind most metals, iron, stainless steel, and other materials.

Before exploring the hardness of white fused aluminum oxide, we have to figure out the principle, method, and numerical meaning of testing hardness first.

There are several hardness testing methods:

• Mohs hardness
• Rockwell hardness
• Vickers hardness
• Knoop hardness.

Mohs hardness and Vickers hardness are methods by scratching. Rockwell hardness and Knoop hardness are methods by static loading.

1. Mohs hardness (Mohs).

It is a relative hardness. 10 kinds of natural minerals are selected as the basic standard of hardness. The surface of the mineral is scratched with a conical diamond drill. The depth of the scratch shows the hardness. The hardness distribution of the ten minerals is:

The practical meaning of Mohs hardness also lies in the fact that scratches are produced only when a material with high Mohs hardness is scratched with a material with low Mohs hardness. Therefore, when grinding a material, we will choose an abrasive with a higher Mohs hardness than the substrate itself.

2. Rockwell hardness (HR) Use a diamond cone (HRC) or hardened (tungsten) steel ball indenter (HRB, etc.) with a preload of 10kgf and the main test force of 60, 100, or 150kgf to measure the surface of the material. The hardness value is then calculated from the depth dimension of the indentation.

3. Vickers hardness (HV) With a test force of 1-120kgf, press a square-cone diamond indenter with an angle of 136° to the surface of the material. The indentation is observed and measured by video using a microscope or a USB camera. The hardness value is calculated according to the size of the indentation diagonal and is generally suitable for the hardness determination of larger workpieces and deeper surface layers.

4. Knoop hardness (HK), also known as Knoop hardness, is a kind of microhardness, which uses a small force to indent a pyramid diamond indenter with an α angle of 172.5°/β angle of 130° between the top two edges. The material is pressed and the hardness value is calculated from the diagonal size of the indentation. Knoop hardness is generally used in metallographic and metallographic research and is suitable for the detection of hard and brittle materials.  Such as enamel, synthetic diamond, cermet, glass, and other materials. There is a fixed conversion relationship between Knoop hardness and Vickers hardness.

It is a good way to compare white fused aluminum oxide and substrate material. By doing so, users could get a basic clue to choose proper abrasive media.
The hardness of abrasive media is generally measured by Mohs hardness. However, the standard of Mohs hardness is relatively rough. In this case, we still get proper technology to get harder white fused aluminum oxide as an experienced white fused aluminum oxide manufacturer. Those technologies are controlling the smelting time, impurity content, and cooling process. If smelting time is sufficient, smelting in the fixed furnace and water cooked,  the white fused aluminum oxide is better. As a result, the WFA will be low impurity content( especially low Na2O content), high hardness, and strong grinding ability.