Praxair S.T. Technology, Inc.

Thermal Spray

Thermal spraying techniques consist of a heat source such as an arc or flame and a coating material, typically in a powder or wire form, that is melted into small droplets and sprayed onto surfaces at high velocity.

Thermal spray coatings are usually applied to metal substrates and are sometimes applied to plastic or ceramic base materials. They enhance the performance of the component by providing improved wear resistance, corrosion resistance or thermal protection, and are a versatile and effective alternative to other coating methods. Thermal spray coatings are distinguished by their abilities to apply metals, cermets, ceramics, and polymers with minimal porosity and very high bond strengths without melting or substantially heating the substrate.

Coating quality is usually evaluated by measuring porosity, oxide content, macro and micro-hardness, residual stress, and bond strength. As the particle velocities increase, the coating quality usually increases as well.

Different processes of thermal spraying include:

• Detonation spraying (D-gun)
• High-velocity Oxy-fuel (HVOF)
• Plasma spraying
• Wire arc spraying
• Flame spraying
• Cold spray
• High-velocity air fuel (HVAF)
• Spray and fuse