Preparation of Compact Micro-Arc Oxidation Coatings on Aluminum Alloys

Abstract

In this paper, a hard and thin coating with no loose layer was formed on the surface of the aluminum LC4 by bipolar micro-arc oxidation power, and the influence of ratio J of the negative current density to the positive current density on the thickness h and the hardness H of micro-arc oxidation coatings was studied. By SEM and other modern materials testing and analyzing techniques, the microstructures of the micro-arc oxidation ceramic coatings were tested and analyzed. It was showed that the micro-structure is compact, and the ceramic coating almost has non-porous layer.

Precursor Derived Ceramic Method to Fabricate SiC Ceramic Composite Coatings on Metallic Substrates

“…However, these methods are not always practical and cost efficient. For example, because of slower deposition rate, higher deposition temperature, and higher cost and energy consumption, it is difficult to achieve large-scale industrial production of CVD; It is is prone to shrinkage crack to fabricate SiC coatings using sol -gel method; It is very danger to fabricate SiC coatings using electric induced heating method, because the fluid in the hole maybe charged during experiments; The thermal spraying technologies invented by Bin-shi xu [20][21][22][23] et al such as high-speed electric arc spraying, supersonic plasma spraying technology etc have been widely used in restoring and remanufacturing of the surface of old equipment parts. However, most of them require complex equipment such as large-scale power supply, spray gun etc, and is difficult to control because of numerous process parameter.…”

“…The method, by which organic silicon polymer is transformed into SiC ceramic, is interesting, because of its excellent formability and low preparation temperature. Familiar organic precursor includes: polycarbosilane (PCS), polysilazane, polyborosilaxane, polyborosiloxane, poly aluminoxane [23]. The PDC method is used to prepare ceramic coating, ceramic fiber and ceramic matrix composite in many domestic scientific research institutes such as National University of Defense Technology, XiaMen University.…”