Is Cold Spray Method Advantageous for Coatings and Additive...

Is Cold Spray Method Advantageous for Coatings and Additive Manufacturing?

By Manufacturing Technology Insights | Wednesday, January 13, 2021

CS is a solid-state deposition method, used by solid powder particles accelerated by a converging de Laval nozzle to a target substratum at supersonic speeds.

FREMONT, CA: Cold spray is the latest addition to the family of thermal spray technology, which has been used since the last century for depositing thick coatings on surfaces in aeronautic, naval, electrical, and other applications. Cold Spray (CS) is also known as dynamic cold gas spraying. It is essentially an enhancement of the thermal spray technique that allows traditional technology to acquire properties and applications.

CS is a solid-state deposition method, used by solid powder particles accelerated by a converging de Laval nozzle to a target substratum at supersonic speeds. A de Laval nozzle is a tube that is pinched in the center, creating an hourglass-shape. The CS technology is similar to the thermal spray-based processes of High Velocity Oxy-Fuel (HVOF)/ High Velocity Air Fuel (HVAF) coating. Still, it differs from them with their relatively low temperature, usually below the sprayed particles' melting point.

The powder feedstock's vital advantage is its freedom of thermal energy relative to conventional thermal spraying processes. Instead, it is based on the particles' high kinetic energy, eliminating the need to melt typical materials and solidify them quickly after contact. It also decreases the formation of Heat-Affected Zones (HAZ), leading to fewer stressful outcomes.

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Powder particles in CS suffer intense plastic deformation due to their ballistic impact. It contributes to the 'adiabatic shear instability' bonding mechanism that adheres to the substrate when it approaches or exceeds the critical impact rate since its kinetic force is transferred to thermal and mechanical deformation.

Additional CS benefits are:

• Enhanced mechanical properties and tiredness

• No toxic fumes are emitted.

• Retention of original particle phases.

• No separate surface preparation layer is necessary (Grit Blasting).

• High hardness, low solidification stress, and thick coatings.

• No inter-metallic formation in various metals

• Low oxidation and defects.

• Faster feed levels for powder and 100 percent particulate reuse. 

• High density, hardness, and low porosity.   

• Accurate gas temperature monitoring.

• Increased safety because of the absence of particulate high-temperature jets.

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