What Does Fused and Crushed Powder Mean?
Fused and crushed powder is powder formed from a fused solid mass which is then crushed to the appropriate size for spraying. Fusion and crushing techniques produce powders that are consistent in size, shape, color, chemistry and toughness.
The powder is used in thermal spray applications of thermal barrier coatings (TBCs) and high-temperature abradables. These materials are extensively used and applied using atmospheric plasma spray or high-velocity oxy-fuel (HVOF) coating spraying. Fine powder can be used for high-energy plasma applications.
This powder can provide a thermal barrier or abradable coating. The resulting coatings have a significantly improved high-temperature sintering resistance, which enhances the durability and thermal insulation effect of the coating.
Corrosionpedia Explains Fused and Crushed Powder
Fused and crushed powders are a method of producing a stabilized and consistent-shaped powder for spray applications. Applying the powder to the substrate can be accomplished using one or more thermal spraying techniques, such as:
- Plasma spray
- Powder combustion
For example, tungsten carbide cobalt fused and crushed powders are most commonly applied using the atmospheric plasma spray (including high-energy plasma) or HVOF processes. The coatings produced are dense and resistant to fretting wear (no intended sliding motion) for use at temperatures below 930°F (500°C). These coatings have good abrasive wear resistance and excellent erosion resistance. Powders with finer particle sizes can be sprayed to produce a smooth as-sprayed finish that can reduce or eliminate the need for finishing operations. When finishing is necessary, the coatings should always be ground.
Typical applications of fused and crushed powders include:
- Aircraft flap tracks
- Expansion joints
- Compressor air seals
- Compressor stator snap diameters
- Fan blade midspan supports
- Cylinder liners
The technique comprises fusing the raw materials followed by crushing the fused materials to achieve particle size suitable for spray applications. It gives superior quality surface protection and very high temperature use. For example, fused zirconium oxide powders are used in:
- Structural ceramics
- Thermal barrier coatings
- Ceramics pigments
Zirconium oxide refractories tend to be used in applications where temperatures are in excess of 3,452°F (1,900°C). The use of zirconia is growing in line with the trend towards more specialized refractories.