The coronavirus pandemic exposed supply chain weaknesses across many different industries, from shortages in medical equipment (ventilator parts and face shields) to microprocessor chips—it even affected basic products such as eggs and toilet paper. As a result, additive manufacturing (AM) has grown in importance as a tool to mitigate some supply insecurities by 3D printing at the point of care, or simply to reduce the lead time for tooling and parts by printing them directly. With lessons learned from pandemic times, manufacturers in aerospace are also becoming more skilled at using laser AM in particular to extend the lifespan of aircraft parts, which also addresses sustainability concerns.
Maintenance, repair and overhaul (MRO) is a huge business in aviation, and sustaining aircraft lifespan has become more of a concern in this time of constrained supply chain, high inflation and rising interest rates. It is now possible to repair metallic parts and tooling using laser-metal deposition (LMD), also known as directed-energy deposition (DED). Repair, rather than wholesale replacement, can be a cost-effective method to extend a part’s lifespan and save money while avoiding a larger carbon footprint by forging or casting new parts. In the LMD repair process of a damaged or worn part, a new surface is obtained by simply depositing new material where needed, with rapid melting and solidification of blown metal powder into the gap, followed by simple finishing to put the part back into deployment.
A typical application of laser AM might be a blade build-up using LMD with a local shielding gas atmosphere. If the blades are deformed, the workpiece can be scanned and repaired using adapted toolpaths generated by CAM software. For complex part geometries—or if no CAD data is available—a laser scanner can be used for digitalization, or a laser triangulation scanner can be integrated into the working cell and used as a tool. For example, the repair process chain for a metallic part that is either worn or damaged is outlined as follows:
Adaptive preparation of the damaged area by milling
Digitalization of the workpiece with a machine-integrated laser scanner
Numerically controlled toolpath planning and LMD simulation using CAM software
Repair by LMD
The process results in a print that is fully metallurgically bonded and dense. On the material side, almost any metal-powder alloy can be used, with the build-up rate and heat input adjustable for Hastelloy X, as well as Inconel 625 and 718. For sensitive materials such as Ti-64 or Ti-6246, a local shielding gas atmosphere with argon gas can be used to prevent excessive local oxidation.
Adding material is another way to sustain part life via dense, corrosion-resistant coatings. Very high material efficiency can be obtained with feed rates of up to 500 m/min (with high-speed LMD), especially for parts having rotational symmetry. Surface deposition rates of >1000 cm²/min at 100µm/layer are feasible as there is very low dilution and a small heat-affected zone—typically <10-50 µm. Rapid solidification of metallics can lead to superior material properties. For example, the hardness of Inconel 625 can be increased by 30% without affecting corrosion resistance.
Overall, laser AM processes such as LMD offer significant benefits in terms of sustainability and the cost-effective repair of expensive and sensitive components. There are system solutions for any size part with a variety of materials able to be deposited. Lasers can help mitigate current economic concerns over part shortages, material and lead time constraints while sustaining overall aircraft lifespan.
Connect With Us
