Brief description of the hardness of advanced ceramics

Advanced ceramics are known for their excellent mechanical properties, with hardness being one of their most notable and valuable attributes. In high-performance applications in aerospace, electronics, medical and industrial fields, hardness is critical for wear resistance, surface durability and dimensional stability. This paper explores the concept of ceramic hardness, compares it to metals and plastics, and provides detailed hardness data for the major ceramic materials.

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What is hardness?

Hardness is the ability of a material to resist localized plastic deformation, such as indentation, scratching or abrasion. For ceramics, the Vickers Hardness (HV) test is commonly used. In this test, a diamond pyramid-shaped indenter is pressed into the surface of the material under a standard load. The smaller the indentation, the harder the material. Due to their strong ionic/covalent bonding and close-packed crystal structure, advanced ceramics are much harder than most metals and polymers.

Tip: High hardness does not mean high toughness, for example, silicon carbide, aluminum oxide is very hard, but more brittle than metal, easy to break.

Why hardness is so important in advanced ceramic applications

Wear resistance: harder ceramics resist abrasion, thus reducing component degradation.
Accuracy and dimensional stability: Ideal for tight tolerances in precision machining.
Thermal Barrier Coating: Hardness increases resistance to thermal erosion under extreme conditions.
Corrosion and chemical resistance: Hard ceramics maintain structural integrity in harsh environments.

Hardness data for major advanced ceramics

Ceramic materials	Vickers hardness (HV)	Mohs hardness	a type of literature consisting mainly of short sketches
Silicon Carbide (SiC)	2,500 - 3,100	9.5	Excellent abrasion resistance
Aluminum oxide (Al₂O₃)	1,800 - 2,200	9	Affordable and highly durable
Silicon Nitride (Si₃N₄)	1,400 - 1,800	8.5 - 9	Tough and thermally stable
ZTA Ceramics	1,500 - 1,800	- 9	Combination of hardness and toughness
Zirconium oxide (ZrO₂)	1,200 - 1,400	8 - 8.5	High toughness, medium hardness
Beryllium oxide (BeO)	1,200 - 1,400	~9	High thermal conductivity
Aluminum Nitride (AlN)	1,100 - 1,300	~8.5	thermal conductivity
Glass ceramics can be processed	450 - 600	~6	easy processing
Boron nitride (h-BN)	25 - 40	2	Very soft, lubricating properties

*Data is for reference only.

Need help choosing the right ceramic?

Choosing the right ceramic material is critical to ensuring long-term reliability and optimal performance. Whether you need zirconia, silicon nitride, or alumina-based ceramics, our materials provide industry-leading strength, durability, and precision.

Our technical team is here to help - contact us today for expert customized advice for your specific needs.

Hardness comparison table: ceramics, metals and plastics

The bar chart below shows the Vickers hardness (HV) of various engineering materials - from super hard ceramics to common industrial plastics, in order from hard to soft.

Ceramic

Metal

Plastic

*Data is for reference only.

Applications based on ceramic hardness

Mechanical seals (ceramic seals)

Applications: pumps, compressors, agitators and rotating shafts
Materials used: silicon carbide (SiC), aluminum oxide (Al₂O₃), zirconium oxide (ZrO₂)
Reason: Its extremely high hardness ensures excellent wear resistance, low friction and long service life, even under corrosive or high-pressure conditions.

Valve assemblies (dispersion and metering discs, valve seats)

Applications: chemical metering pumps, fuel injection systems, high pressure fluid control
Materials used: alumina, silicon nitride, ZTA, tungsten carbide
Why: High hardness resists erosion and mechanical fatigue, maintaining tight seals and flow accuracy over millions of cycles.

Linear guides and bearing surfaces

Applications: CNC machine tools, wafer processing equipment, sliding mechanisms
Materials used: silicon nitride, zirconium oxide, aluminum oxide
Reason: High hardness provides excellent resistance to surface abrasion and scratching at high speeds or under oscillating motion.

Nozzles (silt, sandblast, fuel)

Applications: sandblasting, slurry pumping, fuel atomization
Materials used: silicon carbide, boron carbide
Why: Excellent hardness minimizes erosion, especially in environments with abrasive media such as sand, alumina powder or mud.

Precision ball bearings and rolling elements

Applications: aerospace gyroscopes, high-speed spindles, dental handpieces
Material used: Silicon Nitride (Si₃N₄)
Reason: Lightweight but extremely hard to reduce fatigue and frictional wear in high speed applications.

Armor and protective components

Applications: personal body armor, bulletproof plates, vehicle armor
Materials used: boron carbide, silicon carbide, alumina
Reason: Among the hardest materials known, advanced ceramics have excellent impact resistance and low density.

Thread guides and yarn tension resets

Applications: textile machinery and automatic reeling systems
Material used: aluminum oxide, zirconium oxide
Reason: Surface hardness resists grooves and nicks caused by continuous friction of threads or wires.

Height pins, dies and stamping tools

Applications: precision stamping, wire drawing, abrasive molding
Materials used: tungsten carbide, silicon carbide
Why: Extremely high hardness allows for consistent dimensional control and long service life during intense repetitive operations.