Cu-Graphite
Cu-Graphite is a powder-metallurgy copper matrix with dispersed graphite, supplied from Cu-Gr5 to Cu-Gr50 plus tin-, lead- and copper-infiltrated variants, giving self-lubrication together with electrical and thermal conduction.
Reference datasheet — Cu-Graphite 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 Cu-Gr10 condition
Cu-Graphite grades and fills
Cu-Graphite is supplied in 8 conditions, soft to hard. Cu-Gr10 is the default FabDigit quotes; the values on this page are for it.
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 | ||
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?
Cu-Graphite is a powder-metallurgy copper matrix with dispersed graphite, supplied from Cu-Gr5 to Cu-Gr50 plus tin-, lead- and copper-infiltrated variants, giving self-lubrication together with electrical and thermal conduction. Default-condition values are 6.4 g/cm³ density, 80 MPa yield, 110 MPa tensile, 2% elongation, 75 GPa modulus and 170 W/m·K, with service to about 300 °C and a machinability rating of 80. It is a brittle, porous sintered body with low strength and modest corrosion resistance (rated 35), so it carries no structural load and cannot be fusion welded. For sliding contacts without a current path, a bronze-graphite or PTFE-filled bearing material is the usual alternative. Cu-Graphite has a density of 6.4 g/cm³ (0.231 lb/in³), heavier than 95% of composite grades. Cu-Graphite has a yield strength of 80 MPa (11.6 ksi) and a tensile strength of 110 MPa (16 ksi) — weaker than 79% of composite grades. Elongation at break is 2% and the elastic modulus is 75 GPa (10.9 Msi).
What is Cu-Graphite used for?
- motor/generator brushes
- current collector shoes
- sliding electrical contacts
- pantograph strips
Advantages
- Conducts heat well — 170 W/m·K (98.2 BTU/hr·ft·°F), better than 94% of composite grades
- Low embodied carbon — 4.2 kg CO₂/kg, better than 88% of composite grades
- Easy to machine — 80/100, better than 85% 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
- Heavy — 6.4 g/cm³ (0.231 lb/in³), worse than 95% of composite grades
- Low strength — 80 MPa (11.6 ksi), worse than 79% of composite grades
Cu-Graphite properties
Typical room-temperature values for Cu-Graphite-Cu-Gr10; bars are the position among composite grades.
Physical1
Cu-Graphite has a density of 6.4 g/cm³ (0.231 lb/in³), heavier than 95% of composite grades.
Mechanical10
Cu-Graphite has a yield strength of 80 MPa (11.6 ksi) and a tensile strength of 110 MPa (16 ksi) — weaker than 79% of composite grades. Elongation at break is 2% and the elastic modulus is 75 GPa (10.9 Msi).
Thermal6
Cu-Graphite is rated for continuous service to 300°C (572 °F). It conducts heat at 170 W/m·K (98.2 BTU/hr·ft·°F), better than 94% of composite grades. Thermal expansion is 13.5 µm/m·K (7.5 µin/in·°F).
Electrical2
Cu-Graphite has an electrical resistivity of 4×10⁻⁸ 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 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's machinability is very good (80/100, better than 85% of composite grades).
Common Calculations5
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 composite family
Yield strength against density for every composite grade FabDigit runs. Cu-Graphite is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Cu-Graphite
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.
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 |
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.
Equivalent designations
Standards and trade names that resolve to Cu-Graphite in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- Cu-Gr
How much does Cu-Graphite cost?
Cu-Graphite is a high-cost composite ($$$$), 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.
Cu-Graphite — frequently asked
What is Cu-Graphite used for?
Cu-Graphite 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?
Cu-Graphite has a typical yield strength of 80 MPa (11.6 ksi) and a tensile strength of 110 MPa (16 ksi) — weaker than 79% of composite grades. Strength varies by condition: see the 8 listed tempers.
Is Cu-Graphite easy to machine?
Yes — machinability is rated very good (80/100, better than 85% 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 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?
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 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?
Cu-Graphite is rated for continuous use to about 300°C (572 °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.
How much does Cu-Graphite cost?
Cu-Graphite is a high-cost composite ($$$$), 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
- 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; 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.