Can a cold, green, supersonic spray save the Black Hawk?

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Wear and tear on U.S. Army helicopters costs as much as $1 billion per decade, yet there was no way to prevent it -- until now.

For more than a decade, the military has been committed to ongoing operations that routinely expose helicopters and other aircraft to a heavy beating. Magnesium alloys are often used in fabrication, and corrosion is a constant problem.

Rotorcraft transmission and gearbox housings take a particularly tough beating, requiring premature replacement of these large, pricey parts.  And that costs the DoD an estimated $100 million per year. The Corpus Christi Army Depot alone has millions of dollars worth of used magnesium housings waiting to be reclaimed.

To address this, the U.S. Army Research Laboratory (ARL) and Sikorsky Aircraft created a “cold spray” method to provide surface protection and reclaim magnesium components.

The Army’s new supersonic spray uses aluminum or alloys to combat aircraft corrosion and reclaim otherwise unsalvageable parts, and it’s just picked up a big award for green technologies.

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Before this breakthrough, critical components could not be restored or reclaimed for service; there was simply no technology available that could restore them.

Sikorsky says it plans to replace the current sump repair technique on the UH-60 Black Hawk with the cold spray -- saving parts and helicopters that would have been written off for future use.

The company hopes to approve the technique for the entire H-60 helicopter family, which includes Black Hawks, Seahawks and more.

How does it work?
A heated, high-pressure gas like helium or nitrogen is channeled into a gun with a nozzle designed to shoot it out at supersonic velocities. The gas carries tiny powder particles at velocities of over 6,000 miles per hour. Each particle is tiny, 50 microns small or even tinier, yet up to 30 pounds an hour of the substance can accumulate.

The gas temperature remains below 1,500 degrees Fahrenheit, so the powder particles don’t melt, oxidize, decompose or degrade. Low heat input means this “cold” spray can be used to coat a broad range of materials, even thinly walled components.

Conventional techniques like thermal sprays or ingot metallurgy can be limiting, and run much, much hotter; cold spray can form unique and exotic coatings and works on a wider range of materials.

ARL, Naval Air Systems Command and Sikorsky Aircraft Company approved the performance standards and objectives for testing at the Fleet Readiness Center in North Carolina.

By reducing the need for and frequency of replacement parts, cold spray will lower cost and improve operational readiness.

With fewer gearboxes needed in the field, shipping back and forth between depots and operating bases for repair would drop, meaning further cost reduction as well.

Supersonic green
Inexpensive, cost-effective and environmentally friendly, the cold spray endeavor -- formally known at the ARL’s Weapons and Materials Research Directorate as the “Supersonic Particle Deposition for Repair of Magnesium Aircraft Components project” -- was named the 2012 project of the year by the Army’s environmental research group.

The awards recognize the significant benefits Victor K. Champagne, Jr, and his team’s research and technology developments have brought to the Department of Defense.

Cold spray does not involve any toxic gases, radiation or chemical reactions and can be incorporated into production and also used in the field downrange for repair.

Beyond its current applications, cold spray also holds potential for repair of gearboxes and other components. If research can push this technology forward, structural repair capability would add cost savings benefits while further enhancing operational readiness.

Early data from tests using cold spray tech with an ARL coating suggest there is promise beyond non-structural or cosmetic repairs -- possibly improving overall strength and durability.

Ballet dancer turned defense specialist Allison Barrie has traveled around the world covering the military, terrorism, weapons advancements and life on the front line. You can reach her at or follow her on Twitter @Allison_Barrie.