Correct Answer - Option 3 : Anodic plasma oxidation
The commonly used surface treatment techniques include:
- Physical vapor deposition
- Chemical vapor deposition
- Ion beam Deposition
- Spraying
- Plasma electrolytic oxidation (PEO)
Most of the above methods involve high processing temperature, which may degrade the coatings and/or substrates.
Plasma anodic oxidation:
- Plasma electrolytic oxidation (PEO): also called Plasma anodic oxidation is a new surface treatment anodizing technique used for growing high-quality oxides at temperatures even lower than those achieved with the high-pressure technique mentioned.
- It is capable of forming well-adhered nanostructured ceramic coatings on metals such as MG alloys, to improve their corrosion and wear resistance.
The use of Plasma introduces the following benefits:
- Development of harder ceramic phases (including crystallization)
- Chemical passivity - most PEO ceramics are chemically inert
- Incorporation of elements from the electrolyte into the ceramic to give different properties
- Reduced stiffness gives high adhesion under mechanical strain or thermal cycling
- Crack-free edges
Surface coatings formed through plasma electrolytic oxidation can offer 2 to 4 times more hardness than hard anodizing or steel, and provide increased wear resistance.
The Plasma Anodic Oxidation process generally follows three stages:
- Oxidation of the substrate
- Plasma modification
- Incorporation of electrolyte elements into the coating.
