TWI Frequently asked questions
by Suman Shrestha
A wide range of surface engineering processes is now available. These processes are often divided into two groups:
- Surface treatments
- Surface coatings
The two groups can be further divided according to the method by which the surface treatment or coating is applied. A typical classification of the more common processes is given below.
| SURFACE TREATMENTS |
| Finishing | Thermal | Diffusion | Ion implantation |
| Grinding | Flame hardening | Carburising | Nitrogen implantation |
| Machining | Induction hardening | Carbonitriding | Carbon implantation |
| Blasting | Laser treatment | Nitriding | |
| Peening | Electron beam treatment | Boriding | |
| | | Aluminising | |
| Typical depth of penetration (mm) |
| 0 | 0.01 - 2.5 | 0.001 - 1 | 0.0001 |
| Typical substrate processing temperatures (°C) |
| 20 - 100 | 800 - 1300 | 400 - 1100 | 20 - 100 |
| SURFACE COATINGS |
| Chemical | Plating | Physical vapour deposition PVD | Chemical vapour deposition CVD | Thermal spraying | Welding | Cladding |
| Paints & polymers | Electro-plating | Vapour evaporation | Moderate temperature | Arc | Gas | Friction |
| Anodising | Electroless | Sputtering | Plasma assisted | Flame | Arc | Electro-spark |
| Electro-phoresis | Hot dipping | Ion plating | Diffusion | Plasma | Laser | Brazing |
| Sol-gel | | | | HVOF | | Explosive cladding |
| Typical thickness of coating (mm) |
| 0.001 - 0.1 | 0.01 - 0.5 | 0.001 - 0.01 | 0.001 - 0.1 | 0.01 - 5 | 1 - 10 | 1 - 10 |
| Typical substrate processing temperatures (°C) |
| 20 - 100 | 20 - 100 | 300 - 600 | 200 - 1000 | 50 - 800 | 600 - 1400 | 400 - 1400 |
Further information
Also available as FAQs:
What is physical vapour deposition (PVD)? What is ion implantation? What is anodising? What is carburising/carbonitriding? What is plasma carburising/plasma nitriding?
