Base elements → Materials → Composite materials

CERAMICS

Table of main properties of technical ceramics

 

Property Typical Value Remarks
Density ~3.0–6.0 g/cm³ Moderate (depends on type: zirconia, alumina, etc.)
Young’s modulus (E) ~200–400 GPa High
Tensile strength ~200–1000 MPa Variable, brittle behavior
Hardness (HV) ~1000–2000 HV Very high
Thermal conductivity ~2–30 W/m·K Low to moderate
Electrical conductivity Very low Insulating material
Thermal expansion ~5–10 ×10⁻⁶ /K Low
Melting point ~1500–2700 °C Depends on composition
Magnetism No Non-magnetic
Corrosion resistance Excellent Chemically inert
Machinability Very difficult Requires diamond tools or laser

Technical ceramics are inorganic, non-metallic composite materials obtained through the shaping and sintering of mineral powders. Introduced into watchmaking in the second half of the 20th century, they are now widely used for their exceptional hardness, wear resistance, and chemical stability.

Unlike metals, ceramics exhibit a brittle behavior (fragile), but offer remarkable resistance to scratches and external aggressions. They are mainly used for external components, but also, more selectively, for technical movement components.

Main Properties

Ceramics used in watchmaking exhibit the following characteristics:

  • Very high hardness (1200 to 2000 HV)
  • Excellent wear and scratch resistance
  • Very good corrosion resistance
  • Non-magnetic material
  • Low thermal expansion coefficient
  • High Young’s modulus (~200–400 GPa)
  • Low thermal conductivity

These properties make them particularly suitable for demanding environments.

1. Zirconia (ZrO₂)

Stabilized zirconia (often yttria-stabilized) is the most widely used ceramic.

Characteristics:

  • Very high hardness
  • Relatively good toughness (compared to other ceramics)
  • Excellent surface finishing capability (mirror polishing)

2. Advanced Technical Ceramics

  • Alumina (Al₂O₃)
  • Carbides (SiC, WC)
  • Nitrides (Si₃N₄)

Used for specific applications requiring:

  • High thermal resistance
  • Enhanced mechanical strength
  • Specific tribological properties

The manufacturing of watchmaking ceramics relies on several key steps:

1. Powder Preparation

  • Selection of fine ceramic powders
  • Addition of binders and additives
  • Homogenization of the mixture

2. Shaping

Different techniques are used:

  • Dry pressing
  • Injection molding (CIM – Ceramic Injection Molding)
  • Isostatic pressing

The resulting part is referred to as a “green part”.

3. Debinding

  • Removal of organic binders
  • Stabilization of the structure

4. Sintering

  • High-temperature firing (≈ 1400–1600 °C)
  • Material densification
  • Volume reduction (controlled shrinkage)

5. Machining and Finishing

Due to their very high hardness, ceramics are difficult to machine and require:

  • Diamond tools
  • Abrasive processes

Possible finishes:

  • Mirror polishing
  • Satin finishing
  • Microblasting

6. Femtosecond Laser Machining (Femto Laser)

For certain technical applications (notably ceramic shafts), advanced processes such as femtosecond laser machining are used:

  • Contactless machining
  • Very high precision
  • No mechanical stresses
  • Enables complex micro-geometries

Ceramics are used for:

External Components

👉 Advantage: scratch resistance and aesthetic stability

Technical Components

  • Shafts (machined using femtosecond laser)
  • Ball bearings (oscillating weights, tourbillon cages, etc.)

Advantages

  • Exceptional scratch resistance
  • High chemical stability
  • Non-magnetic
  • Low aging over time
  • Durable aesthetic appearance
  • Relatively lightweight

Limitations

  • Brittleness (fragile material)
  • Sensitivity to strong impacts
  • Difficult machining
  • Relatively high cost
  • Complex manufacturing process