01-10-2010, 11:38 AM
[attachment=4712]
THERMAL SPRAYING AND HARD FACING
INTRODUCTION
Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface.
The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame).
Thermal spraying can provide thick coatings (approx. thickness range is 20 micrometers to several mm, depending on the process and feedstock), over a large area at high deposition rate as compared to other coating processes such as electroplating, physical and chemical vapor deposition.
Coating materials available for thermal spraying include metals, alloys, ceramics, plastics and composites
Coating quality is usually assessed by measuring its porosity, oxide content, macro and micro hardness, bond strength and surface roughness.
Generally, the coating quality increases with increasing particle velocities.
SEVERAL VARIATION OF THERMAL SPRAYING
- Flame spraying
- High-velocity oxy-fuel coating spraying (HVOF)
- Plasma spraying
- Warm spraying
- Wire arc spraying
