SiC/SiC CVI
Matrix · default condition
also Nicalon/SiC, Hi-Nicalon Type S/SiC
CVI = chemical vapor infiltration matrix
Choose chemical vapour infiltration on a 2D/3D woven preform for aero-engine hot sections needing the highest matrix purity and temperature capability; accept 10–15 % residual porosity and long deposition cycles.
Values for the CVI condition
Other SiC/SiC grades and fills
SiC/SiC is listed in 7 conditions; see the grade overview at SiC/SiC.
Compare all 7 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Nicalon CG fiber reinforcement | Specify this first-generation, lowest-cost fibre only for moderate-temperature or short-life parts; its oxygen-containing, non-stoichiometric structure creeps and loses mass above 1100 °C. | 80 | 250 | 0.4 | — |
Hi-Nicalon Type S fiber reinforcement | Pick the near-stoichiometric, low-oxygen fibre as the default reinforcement for 1300 °C-class engine hot-section parts where creep resistance and 320 MPa strength are required. | 120 | 320 | 0.6 | — |
Tyranno SA3 / Sylramic fiber reinforcement | Choose the highly crystalline fibre with a little sintering aid for the highest temperatures and nuclear service, giving 30 W/m·K and best creep resistance; it is more brittle and limits weaving radius. | 140 | 300 | 0.4 | — |
Nano-infiltration & transient eutectic-phase sintering | Choose nano-infiltration and transient eutectic-phase sintering for nuclear fuel cladding and fusion first walls needing near-theoretical density, 45 W/m·K and gas tightness; hot pressing limits shapes. | 200 | 400 | 0.4 | — |
Polymer infiltration & pyrolysis matrix | Use polymer infiltration and pyrolysis for large, complex, cost-sensitive exhaust and secondary-load structures; the porous matrix gives only 8 W/m·K and 1200 °C capability. | — | 250 | 0.7 | — |
CVIDefaultThis page Chemical vapor infiltration matrix | Choose chemical vapour infiltration on a 2D/3D woven preform for aero-engine hot sections needing the highest matrix purity and temperature capability; accept 10–15 % residual porosity and long deposition cycles. | — | 300 | 0.6 | — |
Melt-infiltrated | Pick melt infiltration for turbine shrouds and combustor liners needing near-full density, 28 W/m·K conduction and good interlaminar strength; free silicon limits use to about 1315 °C. | — | 320 | 0.45 | — |
What is SiC/SiC CVI?
SiC/SiC CVI is SiC/SiC in the CVI condition — choose chemical vapour infiltration on a 2D/3D woven preform for aero-engine hot sections needing the highest matrix purity and temperature capability; accept 10–15 % residual porosity and long deposition cycles. SiC/SiC CVI has a tensile strength of 300 MPa (43.5 ksi), stronger than 53% of composite grades. Elongation at break is 0.6% and the elastic modulus is 230 GPa (33.4 Msi). SiC/SiC CVI has a density of 2.5 g/cm³ (0.0903 lb/in³), heavier than 81% of composite grades.
Advantages
- High service temperature — 1,350°C (2,462 °F), better than 98% of composite grades
- Good UV / weathering resistance — 100/100, better than 93% of composite grades
- Polishes to a fine finish — 55/100, better than 83% of composite grades
- Stiff — 230 GPa (33.4 Msi), better than 82% of composite grades
- Tough — resists crack growth — 25 MPa·√m (22.8 ksi·√in), better than 80% of composite grades
Limitations
- High embodied carbon — 110 kg CO₂/kg, worse than 100% of composite grades
- Difficult to machine — 4/100, worse than 99% of composite grades
- Limited ductility — 0.6%, worse than 88% of composite grades
- Heavy — 2.5 g/cm³ (0.0903 lb/in³), worse than 81% of composite grades
SiC/SiC CVI properties
Typical room-temperature values for SiC/SiC CVI; 10 are specific to this condition. Other listed values are SiC/SiC reference data and may not represent this condition. Bars are the position among composite grades.
Physical1
SiC/SiC CVI has a density of 2.5 g/cm³ (0.0903 lb/in³), heavier than 81% of composite grades.
Mechanical12
SiC/SiC CVI has a tensile strength of 300 MPa (43.5 ksi), stronger than 53% of composite grades. Elongation at break is 0.6% and the elastic modulus is 230 GPa (33.4 Msi).
Thermal6
SiC/SiC CVI is rated for continuous service to 1,350°C (2,462 °F). It conducts heat at 15 W/m·K (8.67 BTU/hr·ft·°F), better than 77% of composite grades. Thermal expansion is 4.3 µm/m·K (2.39 µin/in·°F).
Electrical1
SiC/SiC CVI has an electrical resistivity of 0.1 Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 77% of composite grades. UV resistance is excellent.
Sustainability3
Producing a kilogram of SiC/SiC CVI takes about 1,500 MJ of energy and emits 110 kg of CO₂ — more than 100% of composite grades. Typical recycled content is 0%.
Manufacturability2
SiC/SiC CVI's machinability is not recommended (4/100, worse than 99% of composite grades).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SiC/SiC CVI
Is SiC/SiC easy to machine?
Diamond grinding, ultrasonic, laser or waterjet cutting only; cutting tears the fibers and damages the interphase, so produce holes and contours net-shape at the preform stage.
Can SiC/SiC be welded?
Not weldable. Use Si-based or MAX-phase brazing, glass-ceramic or precursor-conversion joining, or CMC bolts with compliant metal bushings to absorb thermal mismatch.
Can SiC/SiC be formed, bent or molded?
Weave or lay up the SiC-fiber preform to the part contour and deposit the BN interphase, then densify with multiple CVI/PIP cycles or Si melt infiltration; cycle times run to several weeks and tooling must survive above 1000 °C.
What surface finishes work on SiC/SiC?
Seal the surface with a CVI layer, then plasma-spray a Si bond coat plus an ytterbium/yttrium silicate EBC. No plating or anodising; inspect by CT and ultrasonic porosity mapping with infrared thermography.
SiC/SiC 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 |
|---|---|---|
| SiC fiber (Nicalon/Hi-Nicalon Type S/TyrVolume fraction; 2D/3D woven or laid up | 30 – 45 | 38 |
| BN or PyC interphase0.3-1 um interphase controlling fiber debonding | 1 – 4 | 2 |
| free SiOnly in MI melt infiltration; limits maximum use temperature | 0 – 15 | 0 |
| porosityCVI 10–15% MI/NITE <3% | 1 – 15 | 10 |
| SiC matrixdensified by CVI/PIP/MI | ≥ 40 (balance) | — |
SiC/SiC CVI — frequently asked
What is SiC/SiC CVI used for?
SiC/SiC CVI is typically used for turbine shrouds and combustor liners, nuclear cladding research, hypersonic leading edges, rocket combustion chambers and industrial burner components. In short: highest-strength CMC here; strength retained above 1200 °C; turbine hot-section grade.
What is the tensile strength of SiC/SiC CVI?
SiC/SiC CVI has a typical tensile strength of 300 MPa (43.5 ksi) — stronger than 53% of composite grades. Strength varies by condition: see the 7 listed tempers.
Is SiC/SiC CVI easy to machine?
Not especially — machinability is rated not recommended (4/100, worse than 99% of composite grades). Diamond grinding, ultrasonic, laser or waterjet cutting only; cutting tears the fibers and damages the interphase, so produce holes and contours net-shape at the preform stage.
Can SiC/SiC CVI be welded?
Not weldable. Use Si-based or MAX-phase brazing, glass-ceramic or precursor-conversion joining, or CMC bolts with compliant metal bushings to absorb thermal mismatch.
What surface finishes work on SiC/SiC CVI?
Seal the surface with a CVI layer, then plasma-spray a Si bond coat plus an ytterbium/yttrium silicate EBC. No plating or anodising; inspect by CT and ultrasonic porosity mapping with infrared thermography.
Can SiC/SiC CVI be formed, bent or molded?
Weave or lay up the SiC-fiber preform to the part contour and deposit the BN interphase, then densify with multiple CVI/PIP cycles or Si melt infiltration; cycle times run to several weeks and tooling must survive above 1000 °C.
What is the maximum service temperature of SiC/SiC CVI?
SiC/SiC CVI is rated for continuous use to about 1,350°C (2,462 °F), and briefly to 1,600°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SiC/SiC CVI and SiC/SiC NITE?
CVI is the default condition — choose chemical vapour infiltration on a 2D/3D woven preform for aero-engine hot sections needing the highest matrix purity and temperature capability; accept 10–15 % residual porosity and long deposition cycles. NITE: choose nano-infiltration and transient eutectic-phase sintering for nuclear fuel cladding and fusion first walls needing near-theoretical density, 45 W/m·K and gas tightness; hot pressing limits shapes.
Sources
- ASM Handbook Vol.21: Composites — Ceramic Matrix Composites — ASM International (2001)
- ASTM C1275 / C1292 / C1341 — Tensile, Shear and Flexural Testing of CMCs — ASTM International (2018)
- NASA Glenn CMC property compilations for CVI/MI SiC/SiC — NASA (2015)
- Nicalon / Hi-Nicalon / Hi-Nicalon Type S fiber data — NGS Advanced Fibers (2020)
- Tyranno SA3 SiC fiber data — Ube Industries (2019)
- Handbook of SiC/SiC Composites for Nuclear Applications (NITE / ) — ORNL / IAEA (2015)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.