Cold Spray Technology – Application in Aerosapce Repair & Maintenance

In the context of an ever-evolving aerospace industry, ensuring the durability and quality of aircraft components plays a vital role. One significant challenge is that component lifespans often exceed their production time, making replacement parts increasingly scarce. This is where Cold Spray emerges as an advanced solution for restoring and repairing crucial aircraft components.

What Is Cold Spray?

Cold Spray is a solid-state metal coating process that uses a high-velocity gas jet to propel metal powder particles onto the surface that needs coating. Unlike other thermal spray methods, Cold Spray requires much lower temperatures, often below the melting point of the materials, helping to minimize deformation and prevent oxidation impurities in the coating.

Thanks to this property, Cold Spray is suitable for heat-sensitive materials like aluminum and magnesium alloys—both commonly used in aerospace components. This method not only ensures durability but also reduces costs compared to replacing damaged parts.

Learn more: APPLICATION OF TITOMIC KINETIC FUSION (COLD SPRAY) FOR COATINGS

Case Study: Repair of Integrated Drive Generator (IDG)

Background

Over the past decade, an increasing number of FAA-certified thermal spray shops in North America have adopted and developed Cold Spray repair procedures to restore hundreds of high-value aircraft components to their original OEM specifications for both commercial and military aviation. Cold Spray technology, with its ability to create well-bonded, low-porosity, oxide-free metal coatings at low temperatures, has become an attractive solution for restoring cast magnesium and aluminum aircraft components that are sensitive to deformation.

Commercial downstream injection Cold Spray system

Application of Cold Spray in Aerospace Repair

Today, cast magnesium or aluminum housings for Integrated Drive Generators (IDGs) are a prime example of high-value aerospace components frequently repaired with Cold Spray technology. Although these are non-critical components, they are costly to replace, and the repair process can be lengthy.

Integrated drive generator of Boeing 747

IDG is an in-flight power generation device that converts the variable rotational speed of an aircraft engine into a constant speed to drive an AC generator. Typically, IDG housings suffer from corrosion and wear, causing dimensions to go out of tolerance and affecting performance. Many failures occur in tight tolerance, heat-sensitive areas such as stator bores, exciter bores, mounting pads, and mating faces.

Pitting corrosion damage in an APU generator housing of Boeing 747

These areas are challenging to restore dimensionally with traditional thermal spray methods. Therefore, Cold Spray technology has become a cost-effective alternative. Cold Spray-repaired devices are now in use on commercial aircraft such as the Boeing 737NG, 747, and 777, and the Airbus A320, A330, and A340.

Cold Spray Qualification Procedure

The qualification procedure followed by most FAA-certified thermal spray shops includes the following steps:

1. Selecting an appropriate Cold Spray powder material

2. Developing and optimizing Cold Spray process parameters to produce coatings within the required specifications

3. Validating coating properties, often through tests such as ASTM C633 bond strength testing, metallographic examination, and 90º bend testing per the OEM’s repair validation specifications (e.g., Hamilton Sundstrand SPR52). For this specific case, the technical requirements include:

🔹 Minimum bond strength of 3,000 psi (20 MPa)

🔹 Porosity below 2%

🔹 No cracks or lack of bonding

🔹 90º bending around a 6 mm radius without chipping or spalling

Microstructure of a typical Cold Spray grade aluminum-alumina composite (SST A0050) used in the repair of aluminum and/or magnesium castings. The substrate is aluminum 606

IDG Repair Process and Quality Assurance

General guidelines for commercial IDG repair include:

- Removing existing corroded and/or damaged surfaces

- Pre-machining as necessary to facilitate Cold Spray deposition

- Surface preparation, including grit blasting or other methods for increasing surface roughness

- Cold spraying using manual or robotic guns

Robotic Cold Spray application (a) and post-machining operation after Cold Spray (b)

- Post-machining the repair per OEM engineering specifications

- Visual inspection

- Dimensional inspection

- Non-destructive examination

- Finishing (painting and/or anodizing) to improve corrosion protection as needed

Repaired and finished components: a) pilot OD, b) stator bore ID, c) housing mating surface, and d) housing bore

Read more: D523 BOOST PRODUCTIVITY IN METAL REPAIR AND MANUFACTURING

Economic Viability of Cold Spray

The main justification for using Cold Spray in restoring these components is the ability to recover them at a fraction of the cost of OEM replacement—assuming the part is still commercially available. In many cases, the component is simply no longer available on the market. Figure 7 compares the average cost of replacement against the cost of Cold Spray restoration for various types of IDGs.

Cold Spray repair cost versus replacement for various IDGs

Conclusion

Cold Spray represents a major advancement in the aerospace industry, helping reduce costs, extend component life, and meet stringent technical requirements. Thanks to Cold Spray, critical aircraft components like IDGs can be restored with low cost and high quality, ensuring safe and efficient aircraft operations. This technology exemplifies continuous progress in optimizing maintenance and repair in the modern aerospace industry.

Vinnotek - Official Distributor of Titomic Cold Spray Machines in Vietnam

Vinnotek is proud to be the trusted partner and official representative of Titomic in Vietnam—a leader in large-scale additive manufacturing applications. With flexible production capabilities, from tools and spare parts to complex machinery components, Titomic provides an optimal solution for replacing traditional manufacturing methods.

At Vinnotek, we offer a range of Cold Spray machines with various pressure levels—high, medium, and low—to flexibly meet the diverse requirements of each business. With a professional team and a spirit of continuous innovation, we are committed to delivering advanced and efficient technology solutions to help customers improve productivity and production quality.

Contact Vinnotek today to discover groundbreaking technological advancements for your industry!

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