SILICON CARBIDE: A MATERIAL WITH EXCEPTIONAL HARDNESS

Silicon carbide (SiC) is formed from the chemical compound of silicon (Si) and carbon (C) and is one of the most high-performance materials in technical ceramics for hard material technology. The material forms a very stable, diamond-like crystal structure, which is responsible for its exceptionally high hardness and strong resistance to abrasion. Accordingly, silicon carbide is commonly regarded as the “diamond among ceramics.”

Unlike conventional tungsten carbides (e.g., WC–Co), silicon carbide (SiC) is a monolithic ceramic and does not contain a metallic binder phase. As a ceramic material, it offers very high wear resistance and excellent chemical resistance , but is also more brittle than tougher cemented carbide grades.

Crystal structure of the non-oxide ceramic silicon carbide

KEY PROPERTIES OF SILICON CARBIDE AT A GLANCE

Silicon carbide, as a high-performance ceramic, combines properties that often determine service life and process reliability in wear parts – especially when abrasion, temperature and medium act on the component simultaneously:

Very low density: 3.20 g/cm³, therefore significantly lighter than tungsten carbide
Very high hardness: approx. 94 HRA, correspondingly high abrasion resistance, even in particle-laden media
Good heat dissipation:thermal conductivity of approx. 80 W/mK
High dimensional stability under temperature changes:low coefficient of thermal expansion of approximately 4.5 × 10⁻⁶/K (at 400 °C)
High temperature resistance:maximum operating temperature up to approx. 1600 °C depending on the SiC variant.
Corrosion-resistant and wear-resistant even at high temperatures:properties remain stable in many media even at high temperatures

Despite these strengths, the classification remains important: silicon carbide is a ceramic and reacts more sensitively to impact stress and point-like edge loads than tougher grades of carbide.

STRUCTURE AND VARIANTS OF THE MATERIAL IN ENGINEERING

Not all silicon carbide is the same. Depending on the bonding type and manufacturing process, the microstructure and therefore the property profile change. Six core variants have become established in engineering:

Silicon-infiltrated, reaction-bonded silicon carbide (SiSiC, also RBSiC)
A SiC structure that is densified by silicon infiltration. This variant often allows for larger or more complex geometries with high dimensional accuracy and exhibits very good thermal shock resistance.

Pressureless sintered silicon carbide (SSiC)
Very dense, high-purity SiC with high hardness and strong corrosion and wear resistance. This variant is frequently chosen when media are chemically demanding and service life is a key consideration.

Liquid-phase sintered silicon carbide (LPS SiC)
SiC that is densified using sintering additives via a liquid phase. Depending on the system, this results in different strength and high-temperature properties compared to SSiC, making this variant suitable for specific load conditions.

Recrystallized silicon carbide (RSiC)
A high-temperature resistant SiC material, often with higher porosity. It is primarily used in applications where temperature resistance and furnace processes are critical, rather than where maximum density is required.

Nitride-bonded silicon carbide (NSiC)
SiC grains that are bonded together by a nitride bonding phase. This variant is often used in high-temperature environments where dimensional stability and temperature cycling are critical.

Oxide-bonded silicon carbide (OSiC)
SiC with an oxide bonding phase. This variant is common in certain high-temperature and refractory applications, but is usually less prominent for dense wear parts compared to SSiC or SiSiC.

Special forms: In addition, CVD-SiC (a particularly pure SiC coating) and SiC composites are used – especially when very specific requirements regarding surface, purity or temperature behavior are the focus.

Which SiC variant is suitable for your component depends on the key operational requirements, such as temperature range, medium, component geometry, tolerances and mechanical load conditions.

Microstructure before annealing

microstructure-SiC-Si-50-50-after-1000-degrees

Microstructure after annealing

Microstructure: SiC-C-Si 50-50 ceramics after annealing (1000 °C) in air

Microstructure of SiC-C-Si-50-50 ceramics before and after annealing at 1000 °C in air

TYPICAL COMPONENTS MADE OF SILICON CARBIDE CERAMIC

Silicon carbide is used wherever wear, erosion, or corrosion determine the service life of components. As a material, SiC is particularly suitable for components that operate continuously under friction, high temperatures, or aggressive media . In many applications, silicon carbide complements cemented carbide. Under particularly high thermal or chemical stress, silicon carbide can fully take on the material function in certain applications.

In practice, SiC components are primarily found in these forms:

Nozzles, flow elements and linings for abrasive media
Valve components such as seats, balls or guides
Sliding rings, sealing surfaces and bearing points in pumps and units
Wear parts in systems where particles and chemicals act simultaneously
Precision parts where dimensional stability under temperature changes is important

CHEMICAL RESISTANCE IN DEMANDING MEDIA

Silicon carbide (SiC) often demonstrates its strengths where components are exposed to acids, alkalis, or corrosive process media while simultaneously subject to abrasion. Unlike tubgsten carbide with a metallic binder phase, SiC remains stable in many of these environments.

The specific chemical resistance depends heavily on the individual operating conditions. Medium, concentration, and temperature influence the level of stress, as do pH value, oxidizing conditions, and flow effects. The chosen SiC variant also affects the behavior in the process, as the microstructure and any potential secondary phases play a role.

APPLICATION SCENARIOS IN THE PROCESS INDUSTRY AND MECHANICAL ENGINEERING

Oil industry: Valves and nozzles are often made of silicon carbide when abrasive media and corrosive process conditions limit service life.
Chemical industry: Seals and seal-related components often rely on silicon carbide when chemical resistance and low-wear sliding surfaces are required.
Mechanical industry: Bearings, balls and other sliding components benefit from high hardness and good friction properties, especially under continuous load and when dimensional stability must be maintained during temperature changes.
Aerospace: Silicon carbide ceramic is used in hot gas components such as gas turbine blades and turbocharger rotors when temperature resistance and dimensional stability under thermal load are required.

BUY SILICON CARBIDE (SIC) COMPONENTS FROM GRAF HARTMETALL

Are you looking to determine whether silicon carbide is suitable for your application, or whether another technical ceramic such as aluminum oxide might be the right choice? Graf Hartmetall will gladly assist you in selecting the appropriate material and in the production of precision parts , ceramic components , or structural components .

Get a free consultation now – we look forward to your inquiry!