Copper is viewed as a material that will accelerate future aerospace production. For example, the privately funded company Ursa Major delivered a copper-based 3D-printed rocket engine combustion chamber from its additive manufacturing lab in Youngstown, Ohio. A challenge, however, is that the existing supply chain for high temperature metal alloy components is limited. However, development continues.
Dr. Ankit Saharan, Senior Manager of Metals Technology at EOS North America discusses how copper and additive manufacturing can accelerate aerospace production and potentially other areas.

MPF:
How is additive manufacturing better than using traditional methods to work with copper materials?

Saharan:
Well, to be honest, copper is no different than other materials when it comes to additive, so I would say many standard benefits that additive manufacturing offers to other materials still do apply. I can go for better design, better functional integration, supply chain robustness and so on and so forth. I think what we are also quickly realizing is that we can do much finer detail resolution with copper, especially with additive manufacturing, depending on layer thicknesses, depending on laser spot sizes, and it’s beyond what traditional manufacturing can do today. Plus, of course, if you count the amazing possibilities that the new alloys offer, not just in terms of pure copper but talking about traditional alloys like copper chrome zirconium, or we’re talking about NASA alloys like GRCop-42 and 84, GRCop-42 being the rage in the space industry right now. This is just beginning of how we are going to shape the copper story.

And I think copper itself is going to lend a very distinguished mark on the AM side of things as we all know that additive began with aerospace and medical and now it’s taken off, especially on the space side. If we’re talking about space, the concepts of regenerative cooling, the concepts of aerospike engines, the concept of RDRE engines, they’re all possible through additive manufacturing. If we talk about regenerative cooling, it’s not a new concept. Traditionally, you had straight through drill holes through chambers and liners to be able to cool the part, but now to be able to go around the part in a spiral fashion that’s hugging the geometry of your thrust chamber, your liners, you’re getting much more efficient cooling. Same goes for aerospike engines. They are decades old technology that NASA did, but nothing really happened with them until… Companies are starting to explore them right now because additive is offering a way to produce these kinds of hardware reliably and more economically.

MPF:
Now, I know that because copper is a high temperature tolerant material, it’s used primarily in the engine portions of an aerospace application. Are there other uses for copper in aerospace?

Saharan:
Definitely. I think copper… being a very conductive material, it’s primarily not just used from a space standpoint in terms of thrust chambers and liners. It can also be used for heat exchanger applications, which are also prevalent in the industry. Historically, that has been done using AlSi10Mg, which has been the aluminum alloy of the 3D printing market or additive manufacturing market, but people are now realizing that copper offers some unique benefits too, being highly conductive and now being able to process copper in additive manufacturing, especially laser powder bed fusion. They’re realizing they can swap some of the aluminum components with copper ones, albeit to get better thermal connectivity properties.

MPF:
Are there any design tips that an engineer needs to be aware of when working with copper materials in additive manufacturing?

Saharan:
Copper being copper is very exciting and unique in the way that it runs typically much hotter than other materials. By that, I mean is that you have to put a lot more energy in to be able to sustain a stable melt pool. Now the thing with copper is, the more heat you put in, the more heat it dissipates away because it’s an excellent conductor of heat. So that’s where the challenge comes from copper, to be able to manage that, to be able to manage a general melt pool. In general, the heat input or the laser power or other factors required to melt copper reliably result in the copper melt pool being slightly larger than that of other materials. But like I said, but with the advancements in software process and material innovations, new things are becoming possible where we’re trying to see, can we push the limits and go with wall thicknesses of less than 150 microns on pure copper? That would really change the game on the heat exchanger side of technology or application.

MPF:
Why is that?

Saharan:
With the thinner profile, you can pack a lot more of those 10 profiles in a compact fashion and if we’re looking from a heat exchanger standpoint, the more surface I have, the better heat I’ll conduct. And when we’re talking about next generation heat exchanger devices or vapor chambers or those kinds of devices, that’s what’s going to matter. It’s this design that’s going to unlock a lot more for the future.

MPF:
Are there any environmental considerations in working with copper in an additive method?

Saharan:
I don’t think there are any special considerations that are required to what is already known in the industry today. So anyone who’s working and has controls in place for titanium and aluminum can very well do copper as well.

MPF:
Are there any drawbacks that an engineer should be aware of when working with copper and additive, other than the ones you’ve mentioned about how it just dissipates heat so efficiently?

Saharan:
Yes, Yes and no. I mean, copper, like I said, is very challenging and it’s one of the more exciting materials. So historically when people looked at materials and process parameters, it was really easy for them. Say people have an M 290 and they had a parameters on an M 290. Now they wanted to go to an M 400-4, which is a larger machine. What many people do today is, take the parameters that are available on the 290 and then just transfer them one to one and just do minor modifications and you’re at a pretty good starting point.

But that doesn’t work with copper. So because of the highly conductive nature of the material, the process window changes from machine to machine because you have a smaller build plate on the M 290, which is 250 mm, so it’s a smaller heat sink, versus a larger plate on the M 400-4, which is 400 mm and it’s a larger heat sink, so you have to compensate for that in terms of process parameters. So that’s where one challenge is, that process development for copper for different materials essentially means that you’re kind of starting from a little bit farther from scratch. But yes, not like other materials.

MPF:
Now are there any applications for using additive manufacturing and copper in electronics, like printed circuit boards or something along those lines?

Saharan:
There definitely are. Our machines are not going to be able to do a printed circuit board. Printing circuits on a board, that’s not powder bed. There are other technologies that can definitely do that and are doing that, in my opinion, today, but where we would typically shine on the electronic side of things is still whatever applies on the aerospace side. Now we’re talking about the electronic side. We’re talking heat exchangers, vapor chambers, and think about, on a very high level, where would heat exchangers be required in a electronics or in a consumer market would be, all this data that we do. We always talk about how fast we can drive the internet, how fast we can, terabytes of data being stored in the cloud, your photographs and everything. All these are hosted on data centers across the world and all these data centers are hosting all this data and they’re running hot.

Sometimes you have special coolers required to cool down whole buildings because the servers are running so hot and that’s where heat exchangers here would come. Thing is that looking at, “Hey, how can we make efficient thermal management system for cooling the server racks?” for example, that’s one example, if that makes sense. And that’ll have huge implication of how we store data, how we manage data, and how data is especially managed across sites, especially with now, countries requiring that my country’s citizens’ data should remain within my borders because it’s a challenge with data. Once it’s in the cloud, it’s in the cloud. It doesn’t have any physical location.

MPF:
So, are we working predominantly with pure copper or copper alloys? What’s the range there?

Saharan:
I would say on the applications that require pure conductivity, like heat exchange or vapor chambers and such, people are primarily using pure copper and very low copper alloys. By low copper alloys, I mean mainly copper, but with small additions added for better processability or other properties that are desired. On the other side where we’re talking about the space industry where we’re talking about better oxidation resistance, where we’re talking about better thermo-conductivity, but at the same time, strength, then we’re talking about alloys like copper chrome zirconium. We’re talking about alloys like GRCop-42, GRCop-84, so it’s a fair mix.

At this point, I would say in an application, if I have to guess, in a guess estimate, an educated guess would be that 80% of the applications today are going to be for alloy copper, like copper alloys, but I would say 20% are going to be for pure copper, low copper alloys, but not just on the electronic side, but also on the automotive side. Think about inductors, think about robo bars or EV vehicles, so that’s a sector which is up and coming as well. So I feel that in the future it’s going to be about 50/50, but right now it’s very heavy on the copper alloy side because the space industry is right now leading the adoption of this material.

MPF:
So at this point, do you think that additive technology is as advanced as it needs to be to deal with the use of copper and the various applications, or is there more technical development for the machinery itself that needs to happen?

Saharan:
I personally believe that we would never be there. It’s a journey. That’s just my personal opinion, but I would definitely say that this is the start. Think about six, seven years ago, and at that time people wanted to do copper, but we were talking about, “Hey, what if the laser is getting reflected back into the optic system? What do I do with a laser back scatter? How do I handle so much heat?” But now we are now talking about how can we do more alloys. How can we do copper with a better strength, with more speed? Because now that’s not a question of whether we can do copper. Now we can do copper, what kinds of copper we can do?

And I think the next thing would be, how fast we can drive the process, because the processes with copper are still relatively slow, but I think with the new advancements in technology, especially on the optic side, whether we’re talking about more powerful lasers, we’re talking about different wavelength lasers, better software technology and being able, to controlling how the scan packs on the laser powder bed fusion machine are getting controlled. I think it’s going to be a game… It’s going to change, but it’s always going to be a journey.

MPF:
Any final thoughts that you might have on copper and additive manufacturing and what’s coming down the pike for the industry?

Saharan:
One thing I would always like to add is, it’s always easy to say that I wanted copper and I want this copper and I want that copper and people get into comparison, which is fair, but it’s very important to realize that every copper is suited for every unique application. It’s not like I can switch pure copper with a copper alloy or a copper alloy with pure copper, depending on what the application demands. And right now there’s always a concern of, especially in the space industry right now, there’s not a debate, I would say, but there’s a seesaw going between GRCop-42 and copper chromium zirconium. We have NASA who’s driving the adoption of GRCop-42 versus traditional copper chrome zirconium available, and there are caveats to both material because GRCop-42, being a newer material, still has to mature its supply chain, whereas on the other side for copper chrome zirconium, the supply chain is much more robust. Even on the pricing points, there are huge differences between the two. Sometimes the differences are three times and four times in prices.

So one thing I would always like to tell folks is, just keep the materials in mind and keep them for what they are. You’re comparing apples and oranges and we would definitely… We’re very soon going to be coming up with a short article basically comparing copper chrome zirconium and GRCop-42, so I’d like to ask your listeners, just keep an eye out for that on LinkedIn. That’s going to come out shortly.
Those are all the questions that I had, so thank you very much for your time, Ankit.

Saharan:
Thank you, Leslie. It was really a pleasure talking to you.