Copper Coating, High Velocity Thermal Sprayed: Dense, Non-Oxidized Brass, Bronze and Cu
Our Kermetico HVAF SL thermal spray system provides an inexpensive way to deposit thick, dense and non-oxidized copper coatings.
The low temperature of the HVAF process, high particle velocity, and inert gas shrouding results in high coating quality and high deposition efficiency for Cu, brass and bronze. HVAF coating is environmentally friendly and much faster than copper plating.
Copper Feedstock Materials
There are two readily available feedstock materials for copper coatings, water atomized and hydrogen reduced copper powder (0.15% oxygen, 0.02% hydrogen). The same is true for the copper-based alloys.
The best copper powder particle size for HVAF spraying is -45/+22 microns (nothing below 15 microns). The absence of fines in the feedstock powder is essential to avoid the formation of oxides.
The Properties Of The Copper Coating
| Feature | Value |
|---|---|
| Apparent metallographic porosity, % | <0.5 |
| Hardness, HV300 | 160-185 |
| Bond strength, MPa | >75 |
| Oxygen content, wt% | 0.30-0.40 |
| Electrical resistivity, micro-Ohm x m | 0.03 |
The coating is near theoretically dense, non-oxidized and exhibits physical properties comparable to bulk (“tough-pitch”) copper. Excellent bonding to steel and aluminum.
A Comparison Of Copper Deposition By HVAF, HVOF And Cold Spray Technologies
The melting point of Cu is 1,084°C (1,983°F), different brass and bronze alloys melt between 900 and 1040°C (1,650 to 1,900°F).
Spraying copper alloys with an HVOF combustion temperature of 2,800 – 3,000°C (5,072 – 5,432°F) results in material melting and oxidation. And with a boiling point of 2,567° (4,653°F) the vaporization of copper in HVOF spraying is certain.
The Cold Spray approach to deposit cold or warm copper powder prevents oxidation, but the cost of cold spray equipment and process makes this type of coating unbearably expensive for most applications.
HVAF combustion occurs at a temperature of 1,960 – 2,010°C, which is still too high for copper. That is why we have developed a dedicated type of HVAF equipment – Kermetico SL, which keeps the temperature of the copper powder below its melting point.
Copper, brass and bronze powders are being preheated below their melting point, accelerated and delivered to the substrate shrouded by an inert gas. This is how we can spray unoxidized dense coatings at a lower cost than HVOF and Cold Spray.
But that’s not all.
The Kermetico HVAF process provides an efficient method to apply thick, inexpensive copper and Cu-based coatings.
We have deposited up to 6 mm (0.250”) for our clients, but that is not the maximum we can apply.
The Typical Applications Of Copper, Brass And Bronze HVAF Coatings
- Heat conductive coating in electronic packaging devices
- Brazing copper layers over aluminum heat sinks
- High electrical conductivity layers on annealing rolls in steelworks
- Restoration of worn parts spraying copper, brass or bronze