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https://www.popularmechanics.com/military/navy-ships/a32744310/submarine-cold-spray-printing/?source=nl&utm_source=nl_pop&utm_medium=email&date=060320&utm_campaign=nl20467749&src=nl

How a Supersonic Metal Spray Could Make Subs Even Deadlier
By Kyle Mizokami Jun 2, 2020

• The Australian Navy is researching cold spray, a form of additive manufacturing, to repair submarines.
• The tech blasts surfaces with tiny bits of metal at high speed, binding it to a surface.
• The process could keep submarines out of shipyards and at sea where they’re needed.

The Royal Australian Navy is investigating so-called “cold spray” technology to repair its six Collins-class attack submarines (pictured above). The tech would allow the service to repair parts on submarines, even the pressure hull, while still at sea. A form of additive manufacturing, cold spray could revolutionize shipboard repairs aboard subs worldwide.

Cold spray involves blasting a damaged metal surface with a supersonic gas filled with metallic particles. The particles fuse with whatever surface it's sprayed upon, forming a buildup of solid metal. The technique takes its name from the fact that, unlike repairs done with welding, the fusing is done far below the melting point. Here’s a video demonstrating cold spray released by ASC, the Australian government organization that builds and maintains the country’s submarine fleet.

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From an engineering perspective cold spray is in some ways better than welding. Welding can damage cold-rolled steel, a type of steel known for its high strength and use in submarine hull construction. This could lead to restrictions on a repaired sub’s diving depth. Cold spray, on the other hand, doesn’t heat the repaired metal’s surface and risk damaging it.

One major advantage of cold spray is that damaged ship parts can be repaired onboard a ship. According to Naval Today, the Australian government is developing portable equipment to be carried on the sub at sea. Submarines are notorious for traveling vast distances, and a submarine that must return to port for a relatively simple repair could lose days or weeks of deployment. Cold spray repairs made underwater would allow the Collins-class boats to remain at sea without having to travel hundreds of miles—or even thousands—of miles to a qualified shipyard.

If Australia can bring cold spray printing to the underwater world of submarines, the technique will likely spread to other navies. We may never have a 3D printer in every home, but few would have thought that additive manufacturing might someday come to every submarine.

Source: Naval Today.