CuW vs CuCr vs AgW: Which Contact Material Does Your Switchgear Need?
Three composite materials cover almost every contact application in medium- and low-voltage switching apparatus: copper tungsten (CuW), copper chromium (CuCr), and silver tungsten (AgW). They are not interchangeable. Pick the wrong one and you either overpay for performance you don't need, or you put a material into a duty it can't survive.
The confusion is understandable. All three are powder-metallurgy composites. All three resist arc erosion far better than plain copper. They share suppliers, datasheets, and a lot of the same vocabulary. But each one earns its place in a different switching environment, and the boundary between them is set by the physics of how the contact interrupts current — not by price alone.
This guide walks through where each material belongs, what drives the choice, and how to avoid the two most common specification mistakes.
The One-Minute Answer
If you only read this far:
- CuCr (copper chromium) — for vacuum switching. Vacuum circuit breakers (VCBs), vacuum interrupters, vacuum contactors, reclosers. CuCr is the standard contact material inside the vacuum bottle.
- CuW (copper tungsten) — for arcing in gas or oil, and for high-voltage duty. SF6 breakers, oil breakers, air-break disconnectors, MV/HV arcing contacts, and high-current conductive parts that take an arc.
- AgW (silver tungsten) — for low-voltage apparatus. Contactors, motor starters, relays, LV breakers. Silver matrix for low contact resistance in continuous LV operation.
The switching medium and voltage class usually settle the choice before cost even enters the conversation. The rest of this article explains why.
Why the Switching Medium Decides Everything
A contact material's job is to survive the arc that forms every time the contacts part under load. What that arc does to the surface depends almost entirely on the environment it burns in. That environment — vacuum, gas, oil, or air — is what separates these three materials.
CuCr is built for vacuum
Inside a vacuum interrupter there is no gas to ionize, so the arc is sustained by metal vapor boiled off the contact surface itself. The contact material has to do three things at once: emit enough vapor to keep the arc stable until current zero, then chop that arc cleanly without dangerous voltage spikes, and re-establish high dielectric strength across the gap within milliseconds.
Copper chromium does this well. The chromium phase getters residual gases inside the bottle and keeps the vacuum clean over thousands of operations, while the copper carries current with low resistance. The two common grades, CuCr25 and CuCr50 (25% and 50% chromium by weight), trade off between current-carrying capacity and dielectric recovery. CuCr is covered in China by GB/T 26867 for vacuum contact technical requirements; equivalent international practice follows the vacuum interrupter manufacturers' own qualification.
Tungsten composites are the wrong choice here. CuW does not emit vapor the way an evacuated arc needs, and its higher melting constituents change the chopping behavior. If your apparatus uses a vacuum bottle, you want CuCr. Our Copper Chromium (CuCr) series covers the vacuum-interrupter contacts, discs, and custom components for this duty.
CuW is built for arcing in gas, oil, and air
Outside vacuum, the arc burns in a gas or oil medium and the failure mode shifts to thermal erosion: the arc root heats one spot on the contact face until material vaporizes. Here the tungsten skeleton earns its place. Tungsten has one of the highest melting points of any metal, so a CuW contact keeps its shape and surface integrity even as the copper matrix locally vaporizes under the arc root.
That makes CuW the standard for SF6 and oil circuit breakers, air-break disconnectors, load-break switches, and the arcing contacts in apparatus where a vacuum bottle isn't used. It also handles the high-voltage end of the range — 40.5 kV and above — where arc energies climb and erosion resistance matters more than the last few points of conductivity.
Grade selection within CuW follows the arc duty. CuW70 keeps more conductivity for standard MV service; CuW80 trades conductivity for more tungsten and better erosion resistance in severe arc duty. The grades are defined in GB/T 8320-2025 for copper tungsten and silver tungsten electrical contacts. Our Copper Tungsten (CuW) series spans the arcing contacts, conductive rods, and shielding components for this family, and the grade choice itself is covered in our copper tungsten grade selection guide.
AgW is built for low-voltage continuous duty
Drop down to low-voltage apparatus — contactors, motor starters, relays — and the priorities change again. Arc energies are lower, but the contact may switch hundreds of times a day and carry continuous current for hours. Contact resistance, and the heat it generates, becomes the dominant concern.
Silver tungsten answers this. The silver matrix gives lower contact resistance than copper at the same tungsten content, which keeps the contact cooler in continuous operation, while the tungsten still provides the arc-erosion resistance an LV contactor needs through its switching life. AgW grades run from roughly AgW30 for lighter duty up to AgW70 and AgW80 for motor and reversing duty. The trade-off between AgW grades is covered in our AgW grade selection guide for AC contactors, and the LV-vs-MV boundary between AgW and CuW is the subject of a separate comparison. The full range sits in our Silver Tungsten (AgW) series.
A Side-by-Side View
| CuCr | CuW | AgW | |
|---|---|---|---|
| Matrix metal | Copper + chromium | Copper | Silver |
| Built for | Vacuum switching | Gas / oil / air arcing | Low-voltage apparatus |
| Typical apparatus | VCB, vacuum interrupter, recloser, vacuum contactor | SF6 / oil breaker, MV/HV disconnector, arcing contacts | Contactor, motor starter, relay, LV breaker |
| Voltage range | MV (vacuum) | MV–HV | LV |
| Dominant concern | Vacuum integrity, current chopping, dielectric recovery | Thermal arc erosion | Contact resistance in continuous duty |
| Standard reference | GB/T 26867 | GB/T 8320-2025 | GB/T 8320-2025 |
The numbers behind these materials — conductivity, hardness, density — fall within published ranges for each grade and standard, but the certified properties for a given lot are confirmed against the order. Use the table to narrow the family; settle the exact grade and properties at the quoting stage.
The Two Most Common Mistakes
Mistake 1: specifying CuW for a vacuum interrupter. This happens because CuW is the better-known "switchgear contact material," and someone carries that habit into a vacuum design. Inside the bottle, CuCr is the right answer. Its vacuum compatibility and chopping behavior are what the application needs; CuW's strengths don't transfer to evacuated arcing.
Mistake 2: paying for AgW where CuW would do, or the reverse. Silver costs far more than copper. Putting AgW into an MV arcing contact wastes money on conductivity the application can't use, while the duty really wants tungsten content for erosion resistance. Going the other way — CuW in a continuous LV contactor — leaves contact resistance higher than a silver-matrix material would, running the contact hotter than it needs to be. Match the matrix metal to the voltage class.
How to Specify Without Guessing
If you know your apparatus, you almost certainly know your material:
- Is there a vacuum bottle? Yes → CuCr. Stop here.
- Is it an arcing contact in gas, oil, or air, or an MV/HV duty? → CuW. Then pick the grade by arc severity (CuW70 standard, CuW80 severe).
- Is it a low-voltage contactor, starter, or relay? → AgW. Then pick the grade by duty cycle.
When the application sits on a boundary, or when you're producing to a drawing that calls out a material you want to second-guess, send us the drawing or a sample. We produce all three families to your specification, and the right material call is part of the conversation before anything gets quoted.
The drawing is the contract. Tell us the apparatus, the switching medium, and the duty, and the material follows from there.