Chromium carbide

Chromium carbide

Chromium carbide (Cr3C2) is an extremely hard refractory ceramic material. It is usually processed by sintering. It has the appearance of a gray powder with orthorhombic crystal structure. Its CAS number is 12012-61-9. The orthorhombic Cr3C2 occurs extremely rarely as mineral tongbaite.

Other compositions are available, eg. Cr23C6 (occurring as extremely rare mineral isovite, cubic) and Cr7C3.

Chromium carbide is used as a thermal spray material for protecting the underlying metal surface, and as an additive to corrosion-resistant and wear-resistant materials. It is used in coatings of bearings, seals, orifices, and valve seals, and as a fine-crystal phase in other sintered carbides, where, like the vanadium carbide, it inhibits growth of submicrometre grains during pressing and sintering. It is highly corrosion-resistant, and does not oxidize even at high temperature (1000-1100 °C). The powder for coating costs $40-$65 per pound.

The thermal expansion coefficient of chromium carbide is almost equal to that of steel, reducing the mechanical stress buildup at the layer boundary.

Precipitation of chromium carbide at the grain boundaries, depleting the grain edges of chromium, is the cause of intergranular corrosion of stainless steel near the welds.

Physical Properties:

  • Density (kg/m³ ): 6,650-6,680 (Cr3C2)
  • Melting point (°C ): 1250 (Cr23C6), 1665 (Cr7C3), 1890 (Cr3C2).

References

External links

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