Cu-Graphite Gr-CuI
Grade
Gr-CuI = copper-infiltrated graphite
Pick when the graphite skeleton must dominate (EDM electrodes, high-speed sliding contacts, pantograph strips) with copper only filling the pores for conductivity.
Values for the Gr-CuI condition
Other Cu-Graphite grades and fills
Cu-Graphite is listed in 8 conditions; see the grade overview at Cu-Graphite.
Compare all 8 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
50 Cu / 50 wt% graphite | Pick where high contact resistance is wanted to limit commutation sparking, or for graphite-dominant self-lubricating pads. | — | 28 | 0.4 | — |
Gr-CuIThis page Copper-infiltrated graphite | Pick when the graphite skeleton must dominate (EDM electrodes, high-speed sliding contacts, pantograph strips) with copper only filling the pores for conductivity. | — | 35 | 0.3 | — |
75 Cu / 25 wt% graphite | Pick for low friction and low brush wear at moderate current density, or for dry self-lubricating bushings. | — | 50 | 0.8 | — |
lead-added copper-graphite (leaded bearing/brush grade) | Pick for very low friction and quiet running on rough commutators/journals where RoHS-exempt lead content is acceptable. | 65 | 90 | 1.5 | — |
Cu-Gr10Default 90 Cu / 10 wt% graphite | Default balance of conductivity, strength and self-lubrication for DC motor brushes and current-carrying bushings. | 80 | 110 | 2 | — |
85 Cu / 15 wt% graphite | Pick when higher contact-drop and better film formation are needed on rough or intermittently loaded commutators. | — | 80 | 1.2 | — |
95 Cu / 5 wt% graphite | Pick for maximum current density and strength where only light self-lubrication is needed (high-current slip rings, grounding brushes). | 120 | 170 | 4 | — |
bronze-matrix (Cu-Sn) graphite grade | Pick when higher strength, wear resistance and better tarnish resistance are needed than plain copper matrix, at some loss of conductivity. | — | 150 | 2 | — |
What is Cu-Graphite Gr-CuI?
Cu-Graphite Gr-CuI is Cu-Graphite in the Gr-CuI grade — pick when the graphite skeleton must dominate (EDM electrodes, high-speed sliding contacts, pantograph strips) with copper only filling the pores for conductivity. Cu-Graphite Gr-CuI has a yield strength of 80 MPa (11.6 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 79% of composite grades. Elongation at break is 0.3% and the elastic modulus is 18 GPa (2.61 Msi). Cu-Graphite Gr-CuI has a density of 2.6 g/cm³ (0.0939 lb/in³), heavier than 83% of composite grades. Cu-Gr10 is the default condition FabDigit quotes; Gr-CuI is available on request or by drawing note.
Advantages
- Easy to machine — 92/100, better than 97% of composite grades
- Conducts heat well — 140 W/m·K (80.9 BTU/hr·ft·°F), better than 90% of composite grades
- Low embodied carbon — 4.2 kg CO₂/kg, better than 88% of composite grades
- Good UV / weathering resistance — 95/100, better than 78% of composite grades
Limitations
- Needs corrosion protection — 35/100, worse than 97% of composite grades
- Limited ductility — 0.3%, worse than 95% of composite grades
- Heavy — 2.6 g/cm³ (0.0939 lb/in³), worse than 83% of composite grades
- Low strength — 80 MPa (11.6 ksi), worse than 79% of composite grades
Cu-Graphite Gr-CuI properties
Typical room-temperature values for Cu-Graphite Gr-CuI; 13 are specific to this condition. Other listed values are Cu-Graphite reference data and may not represent this condition. Bars are the position among composite grades.
Physical1
Cu-Graphite Gr-CuI has a density of 2.6 g/cm³ (0.0939 lb/in³), heavier than 83% of composite grades.
Mechanical10
Cu-Graphite Gr-CuI has a yield strength of 80 MPa (11.6 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 79% of composite grades. Elongation at break is 0.3% and the elastic modulus is 18 GPa (2.61 Msi).
Thermal6
Cu-Graphite Gr-CuI is rated for continuous service to 350°C (662 °F). It conducts heat at 140 W/m·K (80.9 BTU/hr·ft·°F), better than 90% of composite grades. Thermal expansion is 6 µm/m·K (3.33 µin/in·°F).
Electrical2
Cu-Graphite Gr-CuI has an electrical resistivity of 3×10⁻⁶ Ω·m.
Chemical & Environmental3
Corrosion resistance is fair (35/100), worse than 97% of composite grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of Cu-Graphite Gr-CuI takes about 62 MJ of energy and emits 4.2 kg of CO₂ — less than 95% of composite grades. Typical recycled content is 30%.
Manufacturability2
Cu-Graphite Gr-CuI's machinability is excellent (92/100, better than 97% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Cu-Graphite Gr-CuI
Is Cu-Graphite easy to machine?
Machines easily with sharp uncoated carbide, dry, at high speed and light feed — the graphite lubricates but the chips are abrasive dust, so use vacuum extraction and avoid sharp corners in the brittle sintered body.
Can Cu-Graphite be welded?
Not fusion weldable; parts are joined by copper-shunt riveting/tamping, silver brazing on copper-rich areas, or press-fit/clamped assemblies.
Can Cu-Graphite be formed, bent or molded?
Made by die-pressing copper/graphite powder blends (200–600 MPa) and sintering at 850–1000 °C in hydrogen or cracked-ammonia, optionally repressed, coined or copper-infiltrated; no cold forming after sintering.
What surface finishes work on Cu-Graphite?
Faces are ground or lapped to the commutator radius; copper contact areas can be tin- or silver-plated, but the porous graphite-bearing surface does not accept plating or mirror polishing and is usually left as machined.
Cu-Graphite 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 |
|---|---|---|
| C (graphite)Dispersed natural/synthetic graphite flake or powder; 10 wt% ≈ 31 vol% for the default grade | 5 – 50 | 10 |
| SnOptional bronze-matrix addition (Cu-Gr-Sn grades) | 0 – 10 | 0 |
| PbOptional friction modifier in leaded grades only | 0 – 10 | 0 |
| CuElectrolytic copper powder matrix, sintered (press-and-sinter or infiltrated) | balance | — |
Cu-Graphite Gr-CuI — frequently asked
What is Cu-Graphite Gr-CuI used for?
Cu-Graphite Gr-CuI is typically used for motor/generator brushes, current collector shoes, sliding electrical contacts and pantograph strips. In short: self-lubricating conductive composite; standard brush material; brittle, non-structural.
What is the yield strength of Cu-Graphite Gr-CuI?
Cu-Graphite Gr-CuI has a typical yield strength of 80 MPa (11.6 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 79% of composite grades. Strength varies by condition: see the 8 listed tempers.
Is Cu-Graphite Gr-CuI easy to machine?
Yes — machinability is rated excellent (92/100, better than 97% of composite grades). Machines easily with sharp uncoated carbide, dry, at high speed and light feed — the graphite lubricates but the chips are abrasive dust, so use vacuum extraction and avoid sharp corners in the brittle sintered body.
Can Cu-Graphite Gr-CuI be welded?
Not fusion weldable; parts are joined by copper-shunt riveting/tamping, silver brazing on copper-rich areas, or press-fit/clamped assemblies.
What surface finishes work on Cu-Graphite Gr-CuI?
Faces are ground or lapped to the commutator radius; copper contact areas can be tin- or silver-plated, but the porous graphite-bearing surface does not accept plating or mirror polishing and is usually left as machined.
Can Cu-Graphite Gr-CuI be formed, bent or molded?
Made by die-pressing copper/graphite powder blends (200–600 MPa) and sintering at 850–1000 °C in hydrogen or cracked-ammonia, optionally repressed, coined or copper-infiltrated; no cold forming after sintering.
What is the maximum service temperature of Cu-Graphite Gr-CuI?
Cu-Graphite Gr-CuI is rated for continuous use to about 350°C (662 °F), and briefly to 450°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Cu-Graphite Cu-Gr10 and Cu-Graphite Cu-Gr5?
Cu-Gr10 is the default condition — default balance of conductivity, strength and self-lubrication for DC motor brushes and current-carrying bushings. Cu-Gr5: pick for maximum current density and strength where only light self-lubrication is needed (high-current slip rings, grounding brushes). Yield strength is 80 MPa in Cu-Gr10 versus 120 MPa in Cu-Gr5.
Sources
- ASM Handbook Vol.7: Powder Metallurgy — Copper and copper-graphite PM parts — ASM International (2015)
- ASM Handbook Vol.21: Composites — Metal-Matrix Composites — ASM International (2001)
- IEC 60413 — Test procedures for determining physical properties of brush materials for electrical machines — IEC (2005)
- MPIF Standard 35 — Materials Standards for PM Self-Lubricating Bearings — MPIF (2019)
- Metal-graphite brush grade catalogs (Mersen, Morgan Advanced Materials, Schunk) — various (2023)
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.