6.02 Development of additive techniques for the repair, regeneration and life extension of machinery

REFERENCE SPOKE

OTHER SPOKES

PROJECT LEADER
Luigi Maria Galantucci

START DATE
Marzo 2023

END DATE
Febbraio 2026

PROPOSER
Politecnico di Bari

PARTNERS
Politecnico di Torino, Politecnico di Milano, Università degli Studi di Firenze, Thales Alenia Space Italia S.p.A., Prima Additive S.R.L.

6.02 Development of additive techniques for the repair, regeneration and life extension of machinery

This project is based on additive manufacturing techniques for Repairing/Remanufacturing, as opposed to recycling or reuse. These methods now offer the best value-added, resource-efficient approach to end-of-life product recovery.

To repair a component, surface and shape defects may need to be eliminated using traditional subtractive techniques, and then material is added to the surface. Material characteristics are restored by following conditioning, such as heat treatment or surface hardening. To meet dimensional tolerances, surfaces are then finished.
Automation employing of Additive Manufacturing (AM) technologies helps improve repair.

Issues in normal remanufacturing approach are: difficulties or challenges encountered when manually repairing and restoring components. Drawbacks of traditional techniques in the repair and restoration process (i.e dependency on skilled workers and issues related to inconsistency in the output quality).

The project will be articulated in:

Direct Energy Deposition and Cold Spray solutions for repair and life extension.
Repair of metal components with Wire Arc AM technology and analysis of the environmental benefits associated to life extension.
Use of hybrid sources to improve the deposition process and characteristics.
Development of process chains for the repair of components based on the adoption of AM processes, reverse engineering, and conventional technologies (chip removal).

DED has many potentialities: some activities of repair and restoration could be automated using DED; DED deployed in repair and restoration could enhance remanufacturing efficiency. Among the DED processes, Laser Metal Deposition with powder and wire repair will be investigated. The use of wire as filler material allows for a 100% yield, in favour of responsible use of the material and energy required to melt it, as well as enabling ease of storage and overcoming the safety and health issues associated with powder. As regards Cold Spray (CS), it is a solid state deposition process where the adhesion of the powder is obtained by exploiting the kinetic energy obtained by accelerating the powder flow up to supersonic speed. Cold spray allows is particularly attractive for the high deposition rate, the lack of dimensional limits and the high deposition efficiency (up to 99%). With ductility as unique property requested to the materials, cold spray can be used with almost every powder/substrate combination, making possible upgrading of repaired parts and it is attractive also for in-situ repairs.
WAAM will be applied for repairing structural elements made lo lightweight alloys, selected from made-in-Italy top-notch sectors, like the space one. The requirements in the space field are very stringent and even small defects/failures that occur during the manufacturing, testing or integration of the main structural elements could lead to discarding the part with the consequences of waste of resources and investment. WAAM technology could be used to repair or reinforce the structure to recover from such defects or failures as WAAM has the great advantage of allowing material deposition while preserving shell continuity for pressure containment. This project could also help to acquire know-how on this new technology which can also pave the way, not only for the repair, but also to produce large space structures in a more innovative way and with a lower consumption of resources and lower environmental impact.
Laser sources that take advantage of a different wavelength respect the Infrared (IR) one can reduce energy losses, increasing process efficiency. The test of advanced laser technologies, therefore, will lead to an improvement in the state of the art for processing high reflective materials, which are increasingly in demand for applications of manufacturing and repairing of automotive and aerospace parts.
For all AM processes selected will developed specific digital process chains for the repair of components based on the adoption reverse engineering to detect and measure the defects (or wear), conventional machining technologies (chip removal) to remove the defects, additive repair end final finishing again based on machining, generating the g-code for the movement of the heads and tools.

RISULTATI ATTESI

The main expected result is an increased useful life and reuse of components, even of great value and high cost.
Using DED Solutions for Repair and Life Extension vs traditional welding for repairing could give different advantages:

Residual stresses: the substrate is impacted by the material addition, and a lower residual stress could result in less distortion or cracks.
Quality: the quality and performance of the original condition are maintained and repaired parts have better mechanical properties, a lower substrate thermal effect zone, and a higher accuracy.
Geometrical complexity: less time is required to work on complex models or geometries, and no waste material is created.
Automation: processes such as scanning, repairing and remanufacturing could be implemented in the same manufacturing system with the aid of technical information on the specifications of the damaged parts.

An analysis of energy consumption and the life cycle of Repair processes will be performed to assess the sustainability.
For what concerns expected results for the LMD wire activity:

optimization of the process on a reference material, such as carbon or stainless steel, before exploring more challenging materials for laser processes such as aluminium alloys.
Comparative analysis will be conducted between powder-based LMD repair and wire-based LMD repair, considering both technical and economic feasibility, as well as sustainability and efficient and responsible use of resources.

For what concern expected results for the CS activity:

Optimization of the process on reference cases: design of the geometry of the cavity to be filled, optimization of the main process parameters (gas pressure and temperature, stand-off distance, nozzle trajectory).
Mechanical and microstructural characterization of the repaired parts
Exploring the application of CS for upgrade of parts damaged by corrosion/wear.

For what concerns expected results for the WAAM activity:

Optimization of repair strategy to achieve a defect free repairing layer of reported material with a good metallurgical and material properties. The optimization of the repair strategy must also include the correct preparation of the surface before deposition.
Evaluation of environmental benefit related to life extension. Different variables will be considered to evaluate the effectiveness of this approach and define ex-post a guideline to apply the process, such as: thickness and geometry of the feature to be repaired, material to be used, need for thermal treatments.

For what concerns the use of hybrid sources to improve the deposition process and characteristics:

Reducing the energy consumption: respect the IR, other laser wavelengths are far more readily absorbed by many metals, making the laser process smoother and efficient in terms of energy consumption.
Improving the quality of the DED process: different laser wavelengths open up completely new opportunities for the high-quality processing of highly reflective metals.

Increasing the range of material for laser processes: by using different laser wavelengths it is possible to face the challenges with high reflective materials and also to increase the families of materials to be processed with AM.

For all the previous activities it will be developed a proper process chain for the repair of components based on the adoption of AM processes, reverse engineering, and conventional technologies (chip removal). In particular, for the design of repairing procedure (scanning, surface preparation by machining, material deposition, surface finishing), for the characterization of deposited features (surface topography, dimensional accuracy, static mechanical properties, residual stresses, porosities and internal defects), for the prediction of thermal impact on the substrate by FE simulation tools. The Pre repair will be done using Reverse Engineering of damaged part, comparing damaged and undamaged part and evaluating the damaged volume. The Repair phase of damaged volume will be specifically designed for the use of AM procedures, while the for the post- repair the machining tool paths will be automatically obtained for the repaired volume.
One of the valuable results will be the set up of repair for space infrastructure. The advantage is great for the recovery of any failures that could lead to the scrapping of parts with a huge waste of resources. This also affects the way the project is conceived, since to avoid possible failures, the spatial structures are often oversized. Also, in the future the same technology could be envisioned to be used directly in space to support missions based on the Moon.

6.02 Development of additive techniques for the repair, regeneration and life extension of machinery

6.02 Development of additive techniques for the repair, regeneration and life extension of machinery

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