Борид хрома (CrB2)

Identification

Chromium boride (CrB2), also called chromium diboride or monochrome diboride, is a binary inorganic compound of chromium and boron from the group of transition metal borides. CAS number 12007-16-8, related registration numbers 1615228-07-3 and 1821115-27-8. Chemical formula B2Cr, EC number 234-499-3, DSSTox ID DTXSID3093991.

Basic Attributes

• CAS No.: 12007-16-8
• Chemical Formula: B2Cr
• Molecular Weight: 73.62
• Exact weight: 77.99040
• EU number: 234-499-3
• DSSTox ID: DTXSID3093991

Physico-chemical characteristics

• Appearance: Gray powder
• Density: 5.15 g/cm3
• Melting point: 1550 °C
• Solubility in water: insoluble
• Storage conditions: -20 °C

Substance class and structure

Chromium diboride belongs to the refractory borides of transition metals with a hexagonal crystal lattice of the AlB2 type: flat networks of boron atoms alternate with layers of chromium atoms. This structure gives the material high hardness, metallic electrical conductivity and resistance to oxidation when heated. In industry, CrB2 is the most commonly produced and most stable of the phases of the chromium-boron system, along with CrB and Cr2B, making it the main commercial chromium boride. The material is obtained primarily by borocarbothermic or carbothermic reduction of chromium oxide in the presence of boron or boron carbide, followed by grinding into powder and, if necessary, consolidation by sintering or spark plasma sintering into dense workpieces.

Hardness and mechanical properties

According to the Rockwell scale, the hardness of CrB2 is rated in the range of 77-88 HRA. For composites of chromium diboride with chromium carbide Cr3C2 in amounts of 10 and 15 wt. % measured Vickers hardness at room temperature is about 14 and 15 GPa, respectively, which characterizes chromium diboride itself as one of the hardest transition metal borides suitable for wear-resistant applications.

Scope of application

CrB2 powder is used as a component of wear-resistant and heat-resistant coatings applied by spraying or surfacing on metal and ceramic surfaces. The material is in demand in the manufacture of cutting tools - drills, milling cutters, replaceable inserts - where it is important to maintain the sharpness of the edge for a long time when processing metals. It is used to make refractory parts of furnaces: crucibles and protective tubes of thermocouples, operating at high temperatures and subject to thermal shocks up to 1316 °C. Electrical conductivity allows chromium diboride to be used in electrical contacts to reduce transient resistance, and also as a coating for electrostatic cartridges in semiconductor production. In aerospace and defense technology, the compound is used in wear-resistant coatings, armor protection elements and parts operating under conditions of extreme heat and mechanical stress.

Storage and handling

Store tightly at a temperature of about -20 °C, in a dry place, away from moisture and acids. When packaging and dosing the powder, avoid dust and use respiratory and eye protection. According to the WGK Germany classification, the compound is classified as hazard class 3 for water bodies, therefore, flushes and waste powder are prohibited from being discharged into sewers and open water bodies.