Metal additive repair of nickel alloy engine components

3D-printed parts are typically printed using STL files generated from CAD drawings. However, this works only for new-make production where the goal is to produce identical parts conforming to the blueprint. When repairing used parts, however, the repair has to be customized for each individual part because each part wears differently during service.
Additive technology in repairs also offers the possibility of embracing complexity, rather than shying away from it. Chen Keng Nam, executive manufacturing leader at GE AESS in Singapore, has also been involved in the metal additive roll-out.

“This disruptive technology can be used for lots of applications, not only in aviation. When I see beyond the realm of repair into new-make, it’s mind-blowing to see the parts that we can design and print using additive. Now designers are making use of the ability to produce new designs that couldn’t be imagined or manufactured before with traditional methods.”
Iain Rodger, managing director at GE AESS, also sees the potential for metal additive technology in MRO.
“In this part of the supply chain our customers truly value faster turn-around time, and that’s what we are achieving. Using our GE Additive Concept Laser M2 machines typically halves the amount of time it takes us to repair these aircraft parts.”

Engine repair

Rodger says his teams are already using additive technology to repair parts in GE Aviation’s CF6 engines. The next goal is to include parts on the CFM56, the best-selling engine in commercial aviation history.
One example is the repair of high-pressure compressor (HPC) blades that run at high speeds and tight clearances within aircraft engines. The blades are crafted from nickel alloy 718. They face regular erosion and wear and tear that, over time, demand continuous repair and replacement. Repairing these blade tips used to require a long process of cutting, welding and grinding to create the proper shape.
GE Aviation has established an automated additive manufacturing process to repair the HPC blade tips, saving time and costs associated with labor and machining. The team created image-analysis software that maps the shape of a used blade and creates customized instructions for the Concept Laser M2 machine to build a new tip with precise alignment and profile. The 3D-printed part is near-net shape and can be finished with minimal additional processing.
“Productivity has increased with our employees able to repair twice as many parts in a day compared to the conventional repair process. Less equipment is also needed for post-processing so the floor space required is reduced by one-third,” says Rodger.
“Further to that we are currently assessing what we are going to do in turbine parts and other components beyond compressors. Day-to-day, working with customers, they will know that there’s a difference as they will be seeing their parts return to them more quickly.”

Increased sustainability

Beyond the much faster turn-around times possible with metal additive technology in aircraft part repairs, Rodger sees another significant win for GE Aviation, for customers and for the aviation industry more broadly.
“To me one of the significant advantages of additive is it’s sustainability. This is going to allow us to repair more parts and throw fewer parts into the bin, use less energy, generate less waste and have a smaller footprint. Repair capability is a big part of the sustainability journey. As the industry expands and new technology is developed, that will only increase.”
The two big advantages that metal additive provides the site are speed and the near-net-shape product. This allows the team to increase productivity and reduce floor space required. The traditional methods for repairing HPC blades involves a lot of effort to weld the blade and then a lot of additional effort to remove the excess material. By using the Concept Laser M2 metal 3D printers, the repaired blade is very close to the final shape when it comes out of the machine, so it takes much less labor and equipment to achieve the finished profile. “The great dream of additive is to print spare parts on demand without even needing to have an inventory. It’s true that it’s a few years away, but it will happen. But we must also recognize that change can take time, especially in our highly regulated industry, and we have to make efforts to prove that our new methods are as good, if not better, than what has gone before,” concludes Shih Tung Ngiam.