Deposition techniques
Flame spraying
This two-step process (spraying followed by fusing) results in a dense coating and a metallurgical bond. It is easy to automate and can be adapted for the spraying of cylindrical parts.
Process
The flame spray process consists of two steps: firstly, apply powder by thermal spraying with a gun, and secondly, fusing the deposit with a fusing torch. The powder is fed into an oxy-acetylene or oxy-hydrogen gun by injection. It is projected towards the surface at high speed. The hot particles flatten upon impact and interlock both with the base material and each other thus forming a mechanical bond.
This is followed by a fusion treatment to obtain a dense and well-bonded coating on the surface. The applied coating is heated to a temperature between the solidus and liquidus temperature - arround 1000°C.
Typical shrinkage of 15 - 20% occurs during fusing when the melt fills the gaps between the particles.
Typical working range
- Deposition rate: 1-9 kg/hour
- Deposition thickness: 0.1 - 3 mm
- Hardness: 38 - 61 HR
Benefits
- Simple to use: only 2 steps (see above)
- 0.1-3 mm thickness
- Smoother surface than wire
Problems with your flame spraying process?
Flame spraying troubleshooting
| Problem | Cause | Solution |
| Deposit peels off |
1. Poor preparation of the surface (oxidized or oily surface) |
Clean the surface well |
| Cracks |
1. Overheating |
Slower cooling / controlled cooling |
| Porosity |
1. Poor preparation of the surface |
Clean the surface well. |
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