Although both of plasma spray and micro-arc plasma oxidation (MAPO) can deposit ceramic coatings on metallic surface, the microstructure is distinctly different. MAPO coatings consist of inner condense layer and outer porous layer. The condense layer of MAPO with less porosity exhibits superior wear resistance and stable microstructure in contrast to plasma spray. MAPO is feasible for workpieces with complex shape. Hence, MAPO is an excellent candidate for replacing plasma spray in many application of aluminum or magnesium alloy. The comparison between MAPO and plasma spray is listed as following:
The comparison between MAPO and plasma spray
Item |
MAPO |
Plasma spray |
|---|---|---|
Voltage and Current |
High voltage and curent denstiy |
Low voltage and high current density |
Deposition rate |
Fast(1~2μm/min) |
Very fast |
Working Temperature |
Ambient Temperature |
Depends on spray materials. High meltingtemperature of ceramics often leads to bending of substrate when cooling |
Substrate choice |
Only vale metals(eg. Mg, Al, Ti alloys) |
Any of structural materials(platics, metal, ceramics, or composite) |
Conformal coverage |
Good |
Extremely poor due to light-of-sight process |
Microstructure |
Outer porous layer and inner condense layer |
Homogeneous, drop flatting pile-up structure |
Composition of coatings |
Ceramics |
Metal or ceramics |
Adhesion |
Metallurgical interface, extremely excellent |
Mechanical interlock, good |
Wear resistance |
Excellent |
Good |
Flexibility |
Excellent |
Poor |
Enviroment |
Alkaline solution (Eco-friendly) |
Noise(>100dB), strong ultraviolet and infrared radiation |
Optimal thickness |
5um~50um |
5um~2mm |
Cost |
High |
Expensive |