Cold Spray, and CO₂ Snow Cleaning

TUTCO Farnam specializes in the design and manufacture of preheaters engineered for cold spray cleaning, also referred to as CO₂ snow cleaning. Our heaters are crucial in the process for elevating the temperature of carrier gases, such as nitrogen, helium, or custom gas mixtures, to a precisely controlled target temperature under high pressure. This preheating process is a fundamental step, as the heated gas subsequently merges with a solid deposition powder. The gas-powder mixture is then accelerated to supersonic velocities through a de Laval-type nozzle, a critical action for the successful deposition of the coating.

To meet the rigorous demands of cold spray systems, these air heaters are designed to rapidly and consistently achieve their target temperatures. A key technical requirement, that can only be achieved with the heater, is their ability to withstand extremely high watt densities, which is essential for delivering maximum thermal energy within a compact volume. This high-power density is a direct consequence of the technical requirement needed for rapid heating rates and efficient thermal transfer within the confined space of the cold spray system, which our heaters proficiently provide. 

The Cold Spray Cleaning Process 

During the cold spray process, the deposition material exits the nozzle at supersonic velocity, impacting the substrate with significant kinetic energy. Upon impact, the high-velocity particles and the substrate surface undergo plastic deformation. The initial impact of a single spherical particle creates a crater-like depression on the substrate. Simultaneously, the particle itself flattens and spreads radially, filling and conforming to the newly formed cavity. This mechanical interlocking process, occurring at the microstructural level, creates a robust mechanical bond between the particle and the substrate with no thermal effects. 

This bonding mechanism is a key advantage in the application of cold spray technology. Since the materials are not melted, they retain their original microstructures and metallurgical properties. This allows for the successful deposition of a wide range of materials, including those with low melting points or those that are sensitive to oxidation. Furthermore, the absence of a thermal phase change at the interface enables the bonding of dissimilar materials. Employing this method yields a significant advantage over competing thermal spray processes that rely on melting and chemical change to form a bond. 

Cold spray itself is a solid-state coating deposition process. Unlike thermal spray methods that melt the feedstock powder, cold spray relies on the kinetic energy of the particles. The process begins with the introduction of powdered materials—including metals, ceramics, and composites—into a stream of hot, high-pressure gas. The powder particles are accelerated to high velocities, and upon impact with the substrate, they deform and bond without a phase change, building up a dense, thin layer of material.