Graphite Felt
Graphite Felt is a needled carbon-fibre felt, carbonised or graphitised, available as soft felt (SGF, RGF, CF) and higher-purity rigid grades such as RGF-HP.
Reference datasheet — Graphite Felt is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SGF condition
Graphite Felt tempers and conditions
Graphite Felt is supplied in 4 conditions, soft to hard. SGF is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Rayon (viscose)-based, halogen-purified high-purity graphite felt | Use in single-crystal silicon, sapphire and semiconductor furnaces where ash/metal contamination and out-gassing must be minimal. | 0.2 | 12 | 0.08 W/m·K | ||
SGFDefault Soft graphite felt, PAN-based, needled | Default flexible insulation blanket/roll for vacuum and inert-gas hot zones; cheapest and easiest to wrap around cylindrical chambers. | 0.3 | 10 | 0.09 W/m·K | ||
Carbon felt, carbonised only | Lower-cost, higher-resistivity felt for service below ~1600 °C and for redox-flow-battery / filtration electrodes. | 0.4 | 8 | 0.08 W/m·K | ||
Rigid graphite felt board | Pick when the insulation must be self-supporting, machinable to shape, or must resist gas erosion in a vacuum furnace hot zone. | 0.8 | 0.2 W/m·K |
What is Graphite Felt?
Graphite Felt is a needled carbon-fibre felt, carbonised or graphitised, available as soft felt (SGF, RGF, CF) and higher-purity rigid grades such as RGF-HP. At about 0.1 g/cm³ and 0.09 W/m·K it is used as hot-zone insulation to 2200 °C in vacuum and inert-atmosphere furnaces, and as porous electrode felt in redox-flow batteries. It has almost no structural capability (tensile strength around 0.3 MPa, modulus 0.003 GPa), oxidises in air at high temperature, and dusts unless faced. Rigid CFC board is the alternative where the insulation must carry load. Graphite Felt has a density of 0.1 g/cm³ (0.0036 lb/in³), lighter than 99% of ceramic grades. It melts at 3,650°C (6,602 °F). Graphite Felt has a tensile strength of 0.3 MPa (0.0435 ksi), weaker than 99% of ceramic grades. Elongation at break is 10% and the elastic modulus is 0 GPa (4.35×10⁻⁴ Msi).
What is Graphite Felt used for?
- furnace hot-zone insulation
- crystal-growth furnace lining
- electrode felt for redox-flow batteries
Advantages
- Ductile — tolerates forming and impact — 10%, better than 100% of ceramic grades
- Lightweight — 0.1 g/cm³ (0.0036 lb/in³), better than 99% of ceramic grades
- Easy to machine — 95/100, better than 99% of ceramic grades
- High service temperature — 2,200°C (3,992 °F), better than 96% of ceramic grades
Limitations
- Low stiffness — 0 GPa (4.35×10⁻⁴ Msi), worse than 100% of ceramic grades
- Poor heat conductor — 0.09 W/m·K (0.052 BTU/hr·ft·°F), worse than 99% of ceramic grades
- High embodied carbon — 25 kg CO₂/kg, worse than 78% of ceramic grades
Graphite Felt properties
Typical room-temperature values for Graphite Felt-SGF; bars are the position among ceramic grades.
Physical3
Graphite Felt has a density of 0.1 g/cm³ (0.0036 lb/in³), lighter than 99% of ceramic grades. It melts at 3,650°C (6,602 °F).
Mechanical6
Graphite Felt has a tensile strength of 0.3 MPa (0.0435 ksi), weaker than 99% of ceramic grades. Elongation at break is 10% and the elastic modulus is 0 GPa (4.35×10⁻⁴ Msi).
Thermal4
Graphite Felt is rated for continuous service to 2,200°C (3,992 °F). It conducts heat at 0.09 W/m·K (0.052 BTU/hr·ft·°F), worse than 99% of ceramic grades.
Electrical2
Graphite Felt has an electrical resistivity of 0.002 Ω·m.
Chemical & Environmental2
Corrosion resistance is very good (75/100), better than 50% of ceramic grades.
Sustainability3
Producing a kilogram of Graphite Felt takes about 300 MJ of energy and emits 25 kg of CO₂ — more than 74% of ceramic grades. Typical recycled content is 5%.
Manufacturability2
Graphite Felt's machinability is excellent (95/100, better than 99% of ceramic grades).
Common Calculations3
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the ceramic family
Yield strength against density for every ceramic grade FabDigit runs. Graphite Felt is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Graphite Felt
Is Graphite Felt easy to machine?
Soft felt is cut with a razor blade, die or waterjet; rigid board is sawn/milled dry with carbide tools — always use HEPA dust extraction and avoid coolant absorption.
Can Graphite Felt be welded?
Not weldable; joined mechanically with graphite pins, CFC screws, graphite foil clamps or carbonising cement.
Can Graphite Felt be formed, bent or molded?
Supplied as needled roll or press-moulded rigid board; soft felt drapes and wraps to small radii and can be layered/compressed to tune conductivity.
Graphite Felt chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| ash≤500 ppm standard; ≤50 ppm for halogen-purified high-purity grade | 0.01 – 0.5 | 0.05 |
| Nresidual nitrogen in PAN-based, carbonised (non-graphitised) felt only | ≤ 0.5 | 0.2 |
| Cgraphitised carbon fibre; purified grades ≥99.99 % | ≥ 99 (balance) |
What surface finishes work on Graphite Felt?
Optionally faced with graphite foil, CFC skin or SiC/pyrocarbon CVD coating to stop erosion and dusting; halogen purification at ~2000 °C removes metallic ash.
How much does Graphite Felt cost?
Graphite Felt is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Graphite Felt — frequently asked
What is Graphite Felt used for?
Graphite Felt is typically used for furnace hot-zone insulation, crystal-growth furnace lining and electrode felt for redox-flow batteries. In short: lowest-conductivity graphite insulation; 2200 °C in inert atmosphere; no load-bearing capability.
What is the tensile strength of Graphite Felt?
Graphite Felt has a typical tensile strength of 0.3 MPa (0.0435 ksi) — weaker than 99% of ceramic grades. Strength varies by condition: see the 4 listed tempers.
Is Graphite Felt easy to machine?
Yes — machinability is rated excellent (95/100, better than 99% of ceramic grades). Soft felt is cut with a razor blade, die or waterjet; rigid board is sawn/milled dry with carbide tools — always use HEPA dust extraction and avoid coolant absorption.
Can Graphite Felt be welded?
Not weldable; joined mechanically with graphite pins, CFC screws, graphite foil clamps or carbonising cement.
What surface finishes work on Graphite Felt?
Optionally faced with graphite foil, CFC skin or SiC/pyrocarbon CVD coating to stop erosion and dusting; halogen purification at ~2000 °C removes metallic ash.
Can Graphite Felt be formed, bent or molded?
Supplied as needled roll or press-moulded rigid board; soft felt drapes and wraps to small radii and can be layered/compressed to tune conductivity.
What is the maximum service temperature of Graphite Felt?
Graphite Felt is rated for continuous use to about 2,200°C (3,992 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Graphite Felt cost?
Graphite Felt is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- SIGRATHERM soft and rigid graphite felt insulation data sheets — SGL Carbon (2022)
- Carbon and graphite felt / rigid board hot-zone insulation — Kureha / Mersen (2021)
- ASM Handbook Vol. 4 — Heat Treating (furnace insulation materials) — ASM International (1991)
- GB/T 32545 / (industry practice) — SAC (2016)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.