Silicon Carbide Casting

Silicon carbide (SiC) refractory ceramics are among the most widely utilized industrial applications, offering outstanding high temperature resistance, heat shock tolerance, and outstanding mechanical properties.

SiC casting is a cost-effective method of producing large volumes of SiC parts with high density by mixing sand, graphite, binder and floating agents in liquid medium.

Characteristics

Silicon carbide is an exceptionally strong and hard material with low density. It boasts a Mohs hardness rating of 9, second only to diamond, as well as having an elevated melting point and superior thermal conductivity properties.

Manufacturers produce cubic silicon carbide (SiC) through chemical vapor deposition or grow it on carbon-based substrates using gas phase synthesis processes used in semiconductor production. Each method offers its own set of advantages and disadvantages; therefore, companies should carefully assess their production process, environmental conditions, budget constraints and other considerations in order to select the one most suited to them.

RBSC boasts superior corrosion resistance, impact strength, high temperature strength and thermal expansion characteristics that make it an ideal refractory material. It is commonly used in large distillation furnace tower plates, aluminum electrolytic tanks and zinc powder furnaces as a lining refractory, while large blast furnace linings also use this material. Slip casting produces porous preforms before liquid silicon infiltration (LSI); their size and bulk density depend on how much carbon black (CB) has been added into their green bodies.

Aplikacije

Silicon carbide is an innovative multifunctional material with numerous uses across several industries – ranging from abrasives and refractory materials, semiconductors and metal casting – such as metallurgy, automotive, energy and national defense industries. Due to its unique properties it plays a pivotal role in these areas.

Silicon Carbide (SiC) is one of the hardest materials known, found naturally as moissanite in some types of meteorite and corundum deposits; however, most commercially available SiC products are synthetically made.

Granular material with its excellent wear resistance properties makes an excellent material choice for use in thermally and mechanically demanding applications, including refractories, ceramics and nonlinear resistance elements. Furthermore, electrical applications include heating elements and nonlinear resistance elements.

Silicon carbide has multiple uses beyond producing abrasive wheels and other abrasive products, including as a deoxidizer in steelmaking and as an agent to modify cast iron microstructure. Silicon carbide improves nucleation ability of molten steel while simultaneously promoting formation of carbide phases and stabilizing microstructure in cast iron microstructure.

Processes

Silicon carbide (SiC) is an extremely hard, solid polymorph of carbon with an extremely high melting point, Mohs hardness (9.5, second only to diamond) and excellent thermal stability. Although naturally present as moissanite mineral deposits, most silicon carbide used for industrial purposes today is artificially produced through synthetic methods.

Particle gradation of raw SiC combined with slip casting can provide an economical solution to produce porous preforms prior to liquid silicon infiltration (LSI) for reaction-bonded silicon carbide (RBSC), a material with excellent mechanical performance and low porosity for easy shaping.

Sintering transforms RBSC from hexagonal crystal structure into zinc blende crystal structure, producing particles with multimodal, flaky and wrinkled impurities on their surfaces which have difficulty dispersing. Furthermore, nonuniform microstructure formation often occurs as residual Si accumulates locally to weaken pore channels resulting in 35% decrease of elastic modulus.

Materials

Silicon carbide production involves two key raw materials, silica sand and carbon. Silica sand comes from natural quartz stone deposits accounting for 12% of Earth’s crust; its purity must surpass 98.5% to avoid impurities. Carbon comes in the form of petroleum coke, metallurgical coke or pitch coal; its carbon content must fall within 0.5 weight percent while its ash content must also remain below this threshold.

Raw materials are compressed and sintered together in order to produce a green compact with high density, as well as dense sinter (RBSiC) or premium quality SSiC sintering that has superior hardness and can withstand higher temperatures.

Due to its hardness and resistance to oxidation and corrosion, carbon fiber has found use in military applications like ballistic armour plates. Other industrial uses for carbon fibre include mechanical sealing materials, sliding bearings and corrosion-resistant valve plates.