GRCop-42. NASA’s copper alloy, printed on our floor.
A copper chromium niobium alloy developed at NASA Glenn for rocket combustion chamber liners. It moves heat almost like pure copper and keeps its strength past 700 °C, and it is one of two alloys AME runs every week.
GRCop-42 is not a catalogue material. It was developed at NASA Glenn Research Center, matured for additive manufacturing at NASA Marshall in Huntsville, and adopted by the engine programs that print regeneratively cooled chambers. AME built a GRCop-42 fuel injector with NASA and Marshall Space Flight Center under our chief engineer Ken Cooper, and we have run the alloy on our EOS M 400 since.
- Chromium
- 4atomic percent, with 2 at% niobium in copper
- Thermal conductivity
- 290W/m·K at room temperature, approx.
- Use temperature
- 700+°C, continued use
- Density
- 8.89g/cm³
What GRCop-42 is.
GRCop-42 is copper with 4 atomic percent chromium and 2 atomic percent niobium. During atomisation the chromium and niobium combine into Cr2Nb, a hard intermetallic that sits in the copper matrix as fine, stable particles. Those particles pin the grain structure and keep the alloy strong at temperatures where ordinary copper alloys soften, while the matrix stays almost pure copper and keeps conducting heat. The dispersion does not dissolve at high temperature, so the alloy does not overage the way precipitation hardened coppers such as CuCrZr do.
GRCop-84 came first, with twice the chromium and niobium. GRCop-42 halves the alloying content to trade a little room temperature strength for about 15 percent higher thermal conductivity, and NASA’s testing found that above 400 °C the two alloys have nearly the same tensile strength. For a chamber liner, where heat flux is the enemy, that is the right trade.
Properties.
| Composition | Cu, 4 at% Cr, 2 at% Nb |
|---|---|
| Strengthening | Cr2Nb dispersion, thermally stable, does not overage |
| Density | 8.89 g/cm³ theoretical |
| Thermal conductivity | About 285 to 290 W/m·K at room temperature, roughly three quarters of pure copper |
| Tensile at room temperature, LPBF plus HIP | UTS about 360 MPa (52 ksi); yield about 185 MPa (27 ksi); elongation about 30 percent |
| Use temperature | Continued use above 700 °C; characterised by NASA to 800 °C |
| As built density | Above 99 percent; above 99.9 percent after HIP |
| Low cycle fatigue | Comparable to NARloy-Z, the Space Shuttle main engine liner alloy |
Values are typical for laser powder bed fusion material after HIP as reported in NASA and published characterisation work. Program allowables come from your own coupon testing.
Why printing copper is hard, and why it works here.
Copper reflects most of the infrared light a fibre laser puts out and conducts away the heat that does get in, so the melt pool is small, unstable and hungry for power. Pure copper is a notorious LPBF material for that reason. GRCop-42 is more forgiving: the Cr2Nb dispersion raises the absorptivity, and the alloy has been characterised by NASA on the machine class we run, so the parameter window is known. Even so it rewards experience. Spatter, powder handling and the hot isostatic press cycle all need attention, and we have made the mistakes on test builds so that we do not make them on yours.
What it is for.
- Regeneratively cooled combustion chambers and thrust chamber liners, with the cooling channels printed into the wall in one piece.
- Injector faceplates and injector bodies that see combustion gas on one side and propellant on the other.
- Nozzle extensions and throats for small engines.
- Heat exchangers, cold plates and anything that has to pull a lot of heat through a wall and survive.
Additive is what made GRCop practical. Machining channels into a copper liner and closing them out with a jacket is the traditional route; printing the liner and channels together removes the joints, the tooling and months of lead time. How the process works.
Design notes for printed GRCop-42.
- Channel walls to 0.5 mm are achievable; give the design review a chance to check the aspect ratio.
- Every channel needs an inlet and an outlet for powder removal, and a way to verify it is clear.
- Plan for HIP: it closes porosity and is standard for pressure boundary copper parts.
- Sealing faces, bores and manifold interfaces get machining stock and a finish pass.
- Where a smooth channel surface matters for flow, chemical or abrasive flow polishing is available through our finishing partners.
GRCop-42 against the other coppers.
Approximate room temperature conductivity and the behaviour that matters when the part gets hot.
| Alloy | Conductivity | Strength when hot | Strengthening | Printability |
|---|---|---|---|---|
| GRCop-42 | About 290 W/m·K | Holds strength above 700 °C | Cr2Nb dispersion, does not overage | Established LPBF process, NASA characterised |
| GRCop-84 | About 15 percent lower than GRCop-42 | Slightly stronger at room temperature, similar above 400 °C | Cr2Nb dispersion, twice the volume fraction | Printable; the higher strength, lower conductivity option |
| CuCrZr (C18150) | About 320 W/m·K | Overages and softens above about 500 °C | Precipitation hardened, must be aged | Printable; loses strength if it runs hot |
| Pure copper (C10100) | About 390 W/m·K | Soft; no useful strength when hot | None | Difficult with infrared lasers; needs a green laser or very high power |
Selected work
A GRCop-42 fuel injector, printed in Huntsville.
Designed by In Space, built at AME under chief engineer Ken Cooper in partnership with NASA and Marshall Space Flight Center, surface finished by REM, and shown at RAPID + TCT.
Questions we get asked.
What is GRCop-42?
A copper alloy with 4 atomic percent chromium and 2 atomic percent niobium, developed by NASA for rocket engine combustion chamber liners. Chromium and niobium form Cr2Nb particles that keep the alloy strong at high temperature while the copper matrix keeps conducting heat.
Who developed GRCop-42?
NASA Glenn Research Center in Cleveland, Ohio; the GRC in the name stands for Glenn Research Center. The laser powder bed fusion process for the alloy was matured and hot fire tested at NASA Marshall Space Flight Center in Huntsville, Alabama, a few miles from our shop.
What is the difference between GRCop-42 and GRCop-84?
GRCop-84 has twice the chromium and niobium. GRCop-42 gives up a little room temperature strength for about 15 percent higher thermal conductivity, and above 400 °C the two have nearly the same tensile strength. GRCop-42 is the one most engine programs print today.
Can GRCop-42 be 3D printed?
Yes. Laser powder bed fusion is its main manufacturing route. The alloy prints more readily than pure copper because the Cr2Nb dispersion improves laser absorption, and NASA has published parameter and property data for it. Parts are hot isostatically pressed after the build.
How hot can GRCop-42 go?
NASA characterises the GRCop alloys for continued use above 700 °C, with test data to 800 °C. The dispersion that strengthens it does not dissolve at temperature, so it does not overage the way CuCrZr does.
Is GRCop-42 available commercially?
Yes, though the powder is made in small lots by a handful of suppliers and lead times can be long. AME runs it regularly. Tell us early if a program needs it so the powder is on the shelf when the file is ready.
What does GRCop-42 3D printing cost?
More than Inconel 718. The powder is a specialty alloy made in small lots, and the parts almost always go through HIP and finishing. Chambers and injectors are priced by build time and post processing; see the cost guide.
Go deeper.
Inconel 718 3D printing
Composition, properties, heat treatment and ASTM F3055.
ProcessLaser powder bed fusion
How the machine works, the design rules, and LPBF next to powder metallurgy.
ServiceMetal 3D printing service
What the job includes, the specifications, and how to choose a shop.
PricingMetal 3D printing cost
Six cost drivers, typical ranges, and how to bring the number down.
PrimerMetal additive manufacturing
The process families, the standards, and where laser powder bed fusion fits.
LocationMetal 3D printing in Huntsville, AL
Next to Redstone Arsenal and Marshall. Visit the shop.
Request a quote
Send the chamber. We’ll tell you if it builds.
Channels, walls, HIP and finish, read by an engineer who has printed this alloy for NASA.