会社のニュース Case Study: Thermal Gradient-Induced Stress in SiC Components

In high-temperature applications, SiC components are often selected for their excellent thermal resistance.

However, in practical operation, some components exhibit:

• Cracking
• Localized damage
• Reduced service life

Even when temperature limits are not exceeded.

Failure often occurs:

• At edges or corners
• Near contact or constraint zones
• Without uniform deformation

This indicates that:

The issue is not temperature itself, but temperature distribution

A thermal gradient refers to:

Temperature difference within a component

For example:

• Hot zone: 1400–1600°C
• Cooler zone: significantly lower

When a thermal gradient exists:

• Different parts of the component expand differently
• Internal stress is generated

This results in:

Thermal stress without external load

The process can be described as:

1. Non-uniform heating or cooling
2. Differential thermal expansion
3. Internal stress development
4. Stress concentration at critical points
5. Crack initiation

Typical features include:

• Cracks at edges or corners
• Damage near supports or constraints
• No obvious overload signs

Failure appears “unexpected"

Although SiC has:

• Low thermal expansion
• High temperature stability

It still experiences:

Thermal stress when gradients are large enough

Thermal stress is influenced by:

• Temperature difference (ΔT)
• Heating rate
• Cooling rate
• Component geometry
• Support conditions

Temperature alone does not cause failure

Temperature difference does

To reduce thermal gradient stress:

• Avoid rapid heating or cooling
• Ensure more uniform temperature distribution
• Optimize component geometry
• Minimize constraint at supports

Thermal gradient-induced stress is:

An internal stress mechanism caused by uneven temperature distribution

It is independent of external mechanical load.

Many high-temperature failures are not caused by:

• Material strength
• Maximum temperature

But by:

Thermal gradients within the system