Warm spraying-a novel coating process based on high-velocity impact of solid particles

Area of Science:

• Materials Science
• Surface Engineering
• Mechanical Engineering

Background:

• High-velocity solid particle coating processes like cold spraying and aerosol deposition have gained industrial interest.
• Conventional thermal spraying involves melting powder, which can lead to material degradation.
• A need exists for coating methods that offer better control over particle behavior and coating properties.

Approach:

• Introduced a novel coating process termed 'warm spraying'.
• Utilizes high-velocity impact of solid powder particles heated below their melting point.
• Analyzes gas dynamics of particle heating/acceleration and high-velocity impact phenomena.

Key Points:

• Warm spraying significantly lowers the critical velocity required for coating formation.
• It offers superior control over feedstock powder degradation (e.g., oxidation) compared to molten powder processes.
• Enables realization of diverse coating structures, from porous to dense, by tuning particle temperature and velocity.
• Successfully deposited heat-sensitive materials including titanium, metallic glass, WC-Co cermet, and polymers.

Conclusions:

• Warm spraying presents a viable alternative to existing high-velocity coating techniques.
• The process demonstrates significant advantages in material preservation and structural control.
• Potential for broad industrial applications, particularly for heat-sensitive materials.