Short answer: choose GRCop-42 when the copper part has to keep its strength and creep resistance at high wall temperatures over many thermal cycles. The classic case is a regeneratively cooled rocket chamber liner. Choose CuCrZr when the part runs cooler and needs high room-temperature yield strength after aging, for example cold plates, induction tooling or moderate-temperature heat exchangers. Before you compare powders, find out the hottest wall temperature, how long the part stays there, and every brazing, HIP or deposition cycle the part sees after printing. Those exposures decide more than the conductivity on a datasheet.
The two alloys are hardened in different ways, so their data cannot be swapped. CuCrZr is precipitation hardened: its strength comes from fine chromium and zirconium precipitates formed during aging, and later heat can coarsen them. GRCop-42 is dispersion strengthened by Cr₂Nb particles, which NASA developed for high-heat-flux liners with oxidation and blanching resistance.
For quotations, see the GRCop-42 powder and CuCrZr powder grade pages, which carry chemistry windows, particle sizes and list prices (EXW China, from 1 kg).
Decision table
| Part duty | Start with | Main risk | Evidence to request |
|---|---|---|---|
| Rocket chamber liner, nozzle with integral channels | GRCop-42 | Thinner property base than GRCop-84; oxygen and Fe control | HIP’d tensile, conductivity, LCF or creep at service temperature, hot-fire plan |
| Liner with the highest cycle-life margin | GRCop-84 (wider design base; 280 vs 344 W/(m·K) extruded) | Lower conductivity raises wall temperature | Same as above, from the GRCop-84 route |
| Cold plate, heat sink, induction coil at moderate temperature | CuCrZr | Wrong aging route for the target (strength or conductivity) | Paired yield strength and % IACS in one heat-treated condition |
| Part that is brazed, HIP’d or clad after printing | Check both | Later thermal cycles over-age CuCrZr | Properties measured after the full thermal history |
| Conductivity first, little load | Pure copper | Low strength; laser coupling | See the CuCrZr vs pure copper guide |
What GRCop-42 is
GRCop-42 is Cu-4 at.% Cr-2 at.% Nb. NASA Glenn developed it by halving the chromium and niobium of GRCop-84 (Cu-8 at.% Cr-4 at.% Nb), giving up some strength for higher thermal conductivity (NASA, 2004). In weight percent, NASA’s powder chemistry for additive manufacturing is 3.1–3.4% Cr and 2.7–3.0% Nb, balance copper. The alloy contains about 7 vol.% Cr₂Nb (Gradl et al., AIAA 2019-4228).
NASA and industry partners then developed laser powder bed fusion for GRCop-42 and ran hot-fire tests on printed liners. One printed GRCop-42 liner accumulated more than 168 starts and more than 7,400 seconds in LOX/hydrogen testing (Gradl et al., 2019). NASA reported more than 41,000 seconds and 1,100 starts on over 30 GRCop-42 and GRCop-84 chambers by 2022 (Gradl et al., IAC 2022). These are NASA program results for specific powders, machines and designs. They show that the alloy can work; they do not qualify any other powder lot or part.
Property evidence, with conditions
The table collects published values for each alloy. They come from different sources, machines and heat treatments, so they show the trend between the alloys, not a side-by-side test.
| Property | GRCop-42 | CuCrZr |
|---|---|---|
| Thermal conductivity, room temperature | 344 W/(m·K), extruded, about 100–125 ppm Fe (NASA 2004); 85% IACS (NASA 2019) | 76% IACS, 325–340 W/(m·K) after a strength-oriented heat treatment (partner LPBF series); ≥85% IACS after a conductivity-oriented treatment (partner datasheet) |
| Tensile / yield, room temperature | 359 / 173 MPa, 32% elongation; LPBF + HIP (NASA 2019, converted from 52 / 25.1 ksi) | 586 / 519 MPa, 22% elongation; LPBF, heat treated, XY (partner LPBF series) |
| Strength at temperature | Nearly equal to GRCop-84 up to 800 °C, extruded (NASA 2004) | 361 / 358 MPa at 500 °C, same heat-treated LPBF series |
| Creep and fatigue | Creep stress for a 15 h life at 500 °C about 25% below GRCop-84; LCF life about half of GRCop-84 at equal strain range (NASA 2004) | Depends on aging state and later thermal exposure; request data for your route |
Three points follow from this table.
- CuCrZr is much stronger at room temperature after aging. In these two data sets its yield strength is roughly three times that of HIP’d GRCop-42. If the part runs near room temperature, CuCrZr usually gives more margin per wall thickness.
- GRCop-42 is designed for the hot side. NASA’s liner work focuses on strength, creep and low-cycle fatigue at wall temperature. NASA lists GRCop alloys for chambers with high strength up to 800 °C (IAC 2022). CuCrZr gets its strength from aging precipitates. In a fusion-materials study, holding CuCrZr at 600–700 °C coarsened the precipitates (PNNL, 2001). Any brazing, HIP or cladding cycle above the aging range has to be part of the CuCrZr property data.
- Conductivity is close, and depends on condition. A conductivity-oriented CuCrZr treatment can reach GRCop-42’s 85% IACS. A strength-oriented treatment drops to the mid-70s. NASA notes that iron picked up from the chromium melt stock lowers GRCop conductivity, and estimates that lower-Fe AM powders gain about 10 W/(m·K) at room temperature (NASA 2019). Specify the condition when you ask for a conductivity value.
The CuCrZr values come from one partner’s published LPBF test series, shown in the CuCrZr powder guide. They are not lot guarantees for either alloy.
The powder specification differs
NASA published practical rules for GRCop powder after qualifying several powder sources (Gradl et al., 2019). They translate directly into RFQ fields.
| Topic | NASA GRCop-42 practice | What to put in the RFQ |
|---|---|---|
| Chemistry | Cr 3.1–3.4, Nb 2.7–3.0 wt.%; target Fe <50 ppm, O <400 ppm; Al and Si <50 ppm | Governing chemistry with Fe and O limits, not only Cr and Nb |
| Atomization | Argon gas atomization; nitrogen forms nitrides and is not acceptable | Atomizing gas |
| Particle size | Spherical, without satellites; sieved to −325 mesh (<45 µm); fines retained | Maximum particle size and whether fines are kept |
| Lot blending | Lots may be combined only if each lot meets chemistry; never blend a high-oxygen lot into a low-oxygen one | Blending rule and lot traceability |
| Packaging | Inert gas or vacuum at all times; argon-backfilled containers, aluminium preferred, no plastic | Container type and backfill gas |
Fines matter more than buyers expect. In NASA’s comparison, one supplier’s −325 mesh powder gave 8.7% elongation with the fines removed and 32.5% with them kept (NASA 2019, Table 2). Production lots in that program keep the fines and cap the maximum diameter at 45 µm.
Our partner screening window for GRCop-42 (D10 ≥15 µm, D50 30–40 µm, D90 ≤60 µm, O ≤0.04%) is shown on the grade page. Its chemistry matches the NASA ranges above, but a D90 of up to 60 µm is coarser than a hard 45 µm maximum. If your program follows the NASA practice, write the maximum particle size and the fines rule into the RFQ, so the cut is agreed before quoting.
For CuCrZr, the open questions are different. State which Zr range your drawing allows (the partner offers 0.03–0.3% and 0.3–0.6% Zr). Then state whether the heat treatment should target strength or conductivity, because one condition cannot maximise both.
Process and post-processing
Both alloys are printed by LPBF. Copper’s reflectivity and conductivity make melting harder than for steel or nickel alloys, so check that the machine and parameter set have been proven on the alloy you are buying. NASA’s GRCop-42 work reached densities above 99.2% before HIP, ran 45 µm layers, and HIP’d all tensile samples. The parameters transferred between two machine sizes with small adjustments (NASA 2019).
GRCop-42 has also been deposited by blown-powder DED with porosity below 0.1%, but with lower room-temperature tensile strength than LPBF material (Landes et al., 2020). DED needs a coarser particle size than the LPBF cuts on our grade page; ask separately if you plan DED.
For bimetallic chambers, the copper liner is joined to a nickel-alloy jacket by deposition or bonding. That step adds heat to the liner. Our CuCrZr rocket chamber guide and the nickel jacket and hot-fire guide cover the liner-jacket split and its inspection.
Acceptance evidence
Data from GRCop-84, from another powder source, or from extruded material does not transfer to your GRCop-42 part. The same applies between CuCrZr variants. Ask for:
- a lot COA with Cr, Nb (or Cr, Zr), Fe, O, Al and Si, and the PSD with its measurement method;
- the atomizing gas and packaging record;
- density and tensile results from coupons built with that powder on your machine, after your full thermal history (HIP, aging, brazing or cladding cycles);
- conductivity measured by a named method (laser flash for thermal, eddy current or four-point for % IACS) on the same condition;
- LCF, creep or hot-fire evidence where the part duty requires it. That is part qualification, not powder acceptance.
RFQ fields
| Field | What to state |
|---|---|
| Alloy | GRCop-42, GRCop-84 or CuCrZr (with Zr range and any designation such as C18150) and the governing specification |
| Powder | Maximum particle size, fines rule, PSD method; Fe and O limits; atomizing gas |
| Lot and packaging | Single lot or blending rule; inert-gas backfill and container type |
| Process | LPBF or DED, machine and laser, layer thickness if fixed |
| Thermal history | HIP, aging target (strength or conductivity), brazing or cladding cycles |
| Quantity and documents | Sample or production quantity, COA and test reports needed, destination |
Request a GRCop-42 powder quotation or a CuCrZr quotation. Paid samples start at 1 kg. Particle-size availability, documents and delivery are confirmed during review.
Sources
- NASA Glenn, Conductivity of GRCop-42 Alloy Enhanced, Research and Technology 2003 (2004): composition, conductivity, LCF, strength to 800 °C and creep versus GRCop-84.
- Gradl, Protz, Cooper, Garcia, Ellis, Evans, GRCop-42 Development and Hot-fire Testing Using Additive Manufacturing Powder Bed Fusion for Channel-Cooled Combustion Chambers, AIAA 2019-4228: powder chemistry, powder handling rules, fines data, LPBF and HIP tensile results, hot-fire summary.
- Gradl et al., Advancement of Extreme Environment Additively Manufactured Alloys for Next Generation Space Propulsion Applications, IAC 2022: temperature capability and cumulative hot-fire experience.
- Landes et al., Investigation of Additive Manufactured GRCop-42 Alloy Developed by Directed Energy Deposition Methods, 2020: DED porosity and tensile comparison.
- Edwards and Singh, overaging study of a commercial CuCrZr, DOE fusion materials semi-annual progress report, 2001: precipitate coarsening at 600–850 °C.