Can LENS Technology Be Used to Repair the Internal Features of Complex Components?

Core Capability and Principle

Yes, Laser Engineered Net Shaping (LENS) technology, a form of Directed Energy Deposition (DED) additive manufacturing, is uniquely capable of repairing internal features of complex components. Unlike methods requiring line-of-sight, LENS operates by focusing a high-power laser beam into a precise melt pool on the target surface while simultaneously injecting metal powder through a coaxial or multi-jet nozzle. This allows the deposition head to access and repair internal surfaces, such as bore walls, undercuts, and channels, provided there is sufficient access for the nozzle and inert gas flow. This makes it invaluable for restoring worn or damaged internal geometries in high-value parts.

Key Advantages for Internal Repair

The primary advantages of LENS for internal repair are precision, metallurgical bonding, and minimal heat input. It can deposit a wide range of alloys, including stainless steels, nickel-based superalloys like Inconel, and cobalt-based alloys, directly onto the substrate. The process creates a fully dense, metallurgically bonded layer that restores the original material properties or enhances them with a more wear- or corrosion-resistant alloy. Its precision minimizes the amount of subsequent machining required, which is crucial for complex internal features.

Critical Challenges and Considerations

Successful internal repair with LENS presents significant challenges. Accessibility and visibility are the foremost constraints; the deposition head and gas delivery system must physically fit, and real-time monitoring of the melt pool inside a cavity is difficult. Thermal management is also critical, as heat buildup in enclosed spaces can lead to distortion or alter the heat-affected zone. Furthermore, internal repairs often require subsequent heat treatment for stress relief, which must be carefully controlled to not affect the base component.

Integration with Post-Processing and Inspection

Post-repair processing is essential. After LENS deposition, the internal clad layer typically requires precision finishing. Techniques like deep hole drilling or boring, abrasive flow machining, or honing are used to achieve the final dimensional tolerance and surface finish. Non-destructive inspection is particularly challenging internally. Advanced techniques such as borescope-assisted visual inspection, internal dye penetrant testing, or specialized ultrasonic probes are employed to validate the bond integrity and absence of defects.

Industry Applications and Viability

This capability is most valuable in industries where component cost is extremely high. In aerospace, it's used to repair internal cooling channels and seal surfaces in turbine blades and fuel system components. The oil & gas sector uses it to refurbish the internal bores and valve seats of large, costly manifolds and pumps. For power generation, it can repair internal diameters of turbine casings and housings. The economic driver is clear: restoring a $100,000 component with a $10,000 LENS repair and machining operation.