Cold Spray (CS) is an advanced thermal spraying technology. Based on aerodynamic principles, it uses high-temperature and high-pressure gas to carry powder particles, which enter the Laval nozzle of the spray gun axially to generate a supersonic flow. Accelerated to 500–1200 m/s by the spray gun, the powder particles impact the substrate in a fully solid state, undergo plastic deformation, and deposit on the substrate surface to form a dense coating.

It can prepare coatings with high thermal conductivity and high electrical conductivity; has minimal thermal impact on the substrate; features slow grain growth (nanostructural structures can potentially be maintained); achieves a near-forged structure (higher hardness compared to traditional coatings) with stable phase and chemical composition; and the coating thickness can reach over 10 cm.

Cold Spray Principle

Cold Spray (CS) is an advanced thermal spraying technology proposed by Papyrin and his team from the Institute of Theoretical and Applied Mechanics of the Soviet Union in the mid-1980s. Based on aerodynamic principles, it uses high-pressure gas to carry powder particles (1–50 μm) into the Laval nozzle of the spray gun axially, generating a supersonic gas flow. Accelerated to 500–1200 m/s by the high-velocity gas flow, the powder particles impact the substrate (metal, ceramic, glass, etc.) in a fully solid state, and deposit on the substrate surface through plastic deformation to form a dense coating. The gas used is usually nitrogen, helium, or a mixture of the two.

Advantages of Cold Spray

Unlike other spraying methods, Cold Spray does not melt the coating material and forms coatings based on physical principles. Compared with arc spraying, plasma spraying, and HVOF spraying, Cold Spray coatings have almost no oxides and high density. The electrical conductivity of Cold-Sprayed pure copper coatings can reach 90% of that of cast bulk materials, while the electrical conductivity of flame-sprayed and HVOF-sprayed coatings is less than 50% of that of cast bulk materials.

• High deposition efficiency (over 95% for certain materials); low oxide content;
• Dense coatings;
• Capable of preparing coatings with high thermal and electrical conductivity (thermal and electrical conductivity can reach over 90% of the corresponding bulk materials);
• Minimal thermal impact on the substrate;
• Negligible grain growth (nanostructural structures can be maintained);
• Near-forged structure (higher hardness than traditional coatings); no phase or chemical composition changes during spraying;
• Optional nozzles of different shapes; spray beam cross-sectional area can range from 20 mm² to 60 mm²;
• Short spray distance (can be less than 10 mm);
• Coating thickness can exceed 10 cm;
• Recyclable and reusable powder (high powder utilization rate).

Applications of Cold Spray

Cold Spray is suitable for plastically deformable metal powders and composite powders containing plastically deformable materials. The sprayable metals range from low-melting-point zinc to high-melting-point titanium and niobium. Like thermal spraying, Cold Spray operates in a sound-insulated chamber equipped with ventilation, dust collection, and purification devices. Its noise level is much lower than that of HVOF spraying.

Composition of the Cold Spray System

The Cold Spray System consists of the following components: main control cabinet and operation control display screen, main heater, spray gun and nozzle, powder feeder, pipelines, gas and electrical circuits, etc.

Cold Spray Overall Layout Diagram

Cold Spray Structure Schematic Diagram

Key Technical Parameters of the Cold Spray Equipment

• Available Working Gases: Nitrogen, helium, or mixed gases
• Working Pressure: 0–3.5 MPa
• Working Temperature: 0–950℃
• Gas Flow Rate: 3000 L/min (for nitrogen/helium)
• Powder Feeding Rate (Copper Powder): 20–200 g/min
• Powder Particle Size: 1–50 μm
• Spray Distance: 5–50 mm
• Power Consumption: 15–55 kW

1. Control Cabinet and Operation Control Display Screen

• Left Cabinet: Equipped with main power control, heating control power supply, and power regulator. The heating control power supply and regulator are specially developed for Cold Spray applications, with an output power exceeding 50 kW and a ventilation adjustment fan to meet long-term heat dissipation requirements.
• Right Cabinet: Configured with main gas (nitrogen), auxiliary gas (nitrogen), and powder feeding gas (nitrogen). Each gas circuit is equipped with a mass flow controller and a valve; the valve opens slowly and closes quickly under control. In case of failure, sudden pressure drop, or power outage, the system shuts down quickly.
• The control unit emits an audible warning signal and displays error alarm information.
• Independent nitrogen and helium control circuits to meet the requirements of single gas and mixed gas use; the mass flow control settings of the main gas, auxiliary gas, and powder feeding gas can be adjusted according to different gas requirements.
• The operation control display screen adopts a 10-inch Siemens touchscreen to control the operation of the entire system. The touchscreen integrates interfaces for connections to external computers, printers, and networks.

Operation Control Interface

• The main interface displays the overall system process.
• Monitoring data can be displayed on the operation interface; the data changes with temperature and pressure fluctuations.
• Parameters of the used components can be input and viewed during operation.

Main Control Cabinet Technical Parameters

• Voltage: 380VAC 50Hz three-phase five-wire system
• Input Power: 55 kW
• Gas Requirements:

• Gas Quality: Nitrogen 97.7%, Helium 99.995%
• Parameters Controlled and Monitored by the Display Screen:
  • Powder consumption
  • Gas consumption
  • Main gas temperature (gas temperature at the heater outlet)
  • Heater element temperature
  • Output power of the heater control power supply
  • Main gas pressure
  • Powder feeding gas consumption
  • Powder feeding gas pressure
  • Nozzle gas temperature
  • Nozzle pressure

2. Main Heater

Temperature Regulation of the Main Heater

The main heater is the core component of the Cold Spray system. It can heat the main gas to approximately 800℃ within 1–2 minutes. Protection technology is adopted to protect the heater components from overheating damage.

The heater is made of high-temperature resistant materials and placed in a thermal insulation chamber. The thermal insulation chamber ensures continuous operation without overheating the outer shell.

A closed cooling system prevents electrical overheating. The cooling device introduces the heat conducted to the electrical components into the heat exchanger to maintain constant temperature control of the electrical cable assembly.

The main heater is suitable for continuous production.

Main Heater Technical Parameters

• Heating Power: 22.5 kW
• Heating Capacity (Temperature Rise at 4.5 MPa with a nozzle diameter of 2 mm):

3. Spray Gun and Nozzle

The spray gun and its Laval nozzle are important components of the Cold Spray system.

Our company uses various manufacturing technologies to produce a series of high-precision nozzles. The spray gun with nozzles has undergone long-term service testing to meet the Cold Spray production needs of manufacturing and scientific research. The standard nozzle features an integral structure, allowing quick replacement (as shown in the figure below).

• The input side of the spray gun is equipped with a main gas inlet, powder feeding gas inlet, pressure measurement, and temperature measurement sensors to meet the required gas flow and heating power (22.5 kW) for production.
• High-temperature resistant materials are used to ensure a long service life of the spray gun and nozzle.
• The spray gun, nozzle, and cooling accessories are selected according to the Cold Spray process and materials.
• The main gas high-pressure metal hose (800℃, 4.5 MPa) is wrapped with thermal insulation material to avoid temperature loss, including the hose and joints.
• The powder feeder transports powder through a thin high-pressure hose with a metal lining.
• The main gas and powder-carrying feeding gas are fully mixed and preheated in the premixing zone of the spray gun, then injected into the Laval nozzle, and accelerated toward the substrate.

4. Powder Feeder

The powder feeder is specially developed for the Cold Spray system. The powder feeding rate is controlled by the speed of the rotary metering disk. The powder-carrying gas flow transports the powder into the spray gun through a hose, then injects it into the main gas jet flow. The powder enters the nozzle compression chamber through the preheating chamber. The powder feeding gas flow is controlled by a mass flow controller, ensuring stable flow, high feeding precision, and uniform and stable coatings. The volume metering powder feeding rate has minimal variation during the entire spraying process.

The powder feeding repeatability complies with the DIN EN1395-7 standard.

Powder Feeder Technical Parameters