Do you offer anti-oxidation coatings?

Yes. We supply and apply graphited coatings and paints (e.g. GRAFOTERM, GRAFICOAT) that protect graphite and refractory surfaces in furnaces and oxidizing environments, extending component life.

Which carbon felts do you recommend for furnaces?

Soft felt for flexible liners and conformable insulation; rigid felt for panels and stable structures. Choice depends on max temperature, atmosphere (vacuum, inert), and thermal cycle.

Soft felt or rigid felt?

Soft felt follows curves, voids, and irregular geometry and is installed in layers; rigid felt is self-supporting and forms panels and liners with stable geometry. In practice many chambers combine both: rigid where shape is needed, soft to fill and close joints.

How much insulation is needed?

It depends on working temperature, dwell time, and the acceptable shell temperature. Thickness and number of layers are defined from those figures; there is no single value that fits every furnace.

What is the difference between PAN and rayon felt?

They differ in fibre precursor and in purity and outgassing behaviour. The choice follows the contamination requirement of the process and the vacuum level; both variants are available.

Does felt contaminate the load with fibre?

It can shed fibre during handling and in flow zones. This is controlled with surface finishes, with rigid panels on exposed faces, and by avoiding direct gas flow over soft felt.

Carbon/graphite felt rolls and rigid insulation panels

Thermal applications

Furnace thermal insulation

Provides protection against high temperatures in industrial applications with graphite and carbon felts.

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Thermal insulation system

Also known as: Carbon felt insulation · Thermal insulation for vacuum furnaces · Graphite felt insulation · Hot-zone insulation

[ Technical summary ]

Carbon and graphite felt insulation reduces heat loss from the chamber toward the furnace shell. Its low conductivity comes from the fibrous structure, which slows both conduction and radiation between layers, and it is especially effective in vacuum, where convection disappears. It is installed as soft felt to follow shapes, or as rigid panel where the insulation must be self-supporting; most chambers combine both by zone.

[ Problem it solves ]

Keep heat inside the chamber to cut energy consumption and protect the shell, using a material that withstands process temperature and does not degrade in vacuum or inert atmospheres.

Processes

Insulation of heat-treatment furnace chambers
Soft felt liners and rigid panels

Operating conditions

Vacuum and inert atmosphere
High temperature

When it is suitable

The furnace works in vacuum or inert atmosphere
Energy consumption or shell temperature is excessive
The existing insulation has degraded or compacted
The chamber mixes free-form zones with zones needing rigidity

When it may not be suitable

The process runs in air at high temperature without a protective atmosphere
The process cannot tolerate fibre shedding onto the load
The insulation will be exposed to direct impact or abrasion

Process challenges

Heat losses
Fiber contamination
Chamber geometry fit
Incorrect choice between soft and rigid felt

Advantages

Low thermal conductivity
Vacuum stability
Cut-to-size
Soft + rigid combination by zone

Limitations

Oxidation in air above ~400–500 °C
Chemical compatibility with specific atmospheres
Design must account for shrinkage and service life

[ Critical selection variables ]

These variables define the grade and the geometry. Actual values are confirmed against the grade datasheet.

Operating temperatureDecisive
Atmosphere (air, inert, vacuum)Decisive
Thickness and number of layersDecisive
Geometry and tolerancesRelevant
Fiber precursor (PAN or rayon)Relevant
Required purity and allowable contaminationRelevant
Fastening system and jointsRelevant

[ Required material properties ]

Properties that guide selection. Numerical values come from each grade's datasheet.

Critical properties

Thermal conductivity
Thermal shock resistance
Purity
Thermal stability

Secondary properties

Dimensional stability

[ Related ]

[ Frequently asked questions ]

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Technical content reviewed by ESGRAF — Last reviewed: September 8, 2026

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