99 alumina ceramics refers to special engineering ceramics with alumina content higher than 99%. 99 alumina ceramic materials are widely used in medical equipment, petrochemical, electronic appliances and other fields with wear resistance, high hardness and high strength. What is the processing hardness and brittleness of alumina ceramics? Discuss with you below.

Machining hardness of 99 alumina ceramics:

AL203 mainly has three crystal forms, α, β, and γ, among which α-AL203 is relatively stable in crystal form, and almost all of I3 and γ crystals are converted into α crystals at 1300 °C.

In the crystalline form of α-AL203, the atomic bonds formed by aluminum ions and oxygen ions are mostly covalent bonds, ionic bonds or their mixed bonds, so the bonding energy between atoms is high and has strong directionality.

The hardness of 99 alumina ceramics is equivalent to the hardness of carbide cemented carbide, which is several times higher than that of steel. Usually, the density of high-purity alumina ceramics can reach 3980 (Kg-m4).

The tensile strength is 260 (MPa), the elastic modulus is between 350-400 (GPa), and the compressive strength is 2930 (MPa), especially its hardness can reach 99HRA. The strength and hardness of 99 alumina ceramics have decreased.

According to our measurement of the experimental sample, its hardness at room temperature also reaches 70HRA.

Machining brittleness of 99 alumina ceramics:

In general, the microstructure of alumina ceramics is equiaxed grains, which are polycrystalline structures composed of ionic bonds or covalent bonds, so the fracture toughness is low.

Under the action of external load, the stress will cause fine cracks on the surface of the ceramics, and the cracks will rapidly expand and cause brittle fractures. Cracked small gap.

Reasons for the collapse phenomenon:

1. The separation of the cut part of the material and the machined surface is caused by tensile failure, which is not the result of normal cutting.

2. Cracks caused by chipping and cutting deformation generally crack down along the surface of the workpiece. At this time, due to the cutting tensile stress, the cutting and the bonded workpiece matrix are peeled off together to form a chipping phenomenon.

Note: The greater the tensile stress, the more serious the chipping phenomenon, which may lead to the waste of the entire workpiece.