Study On Micro-arc Oxidation Of The Hot-dipping Aluminum Coationgs On Q235

The ceramic coating was obtained by the method of micro-arc oxidation of the hot-dipped aluminum coating on Q235 for the first time. The hot-dipping condition fitting for the micro-arc oxidation was found. The discipline that the technologic parameters influence on the overall thickness and the thickness grown outward and the discipline of the size changing of the sample before and after micro-arc oxidation were studied in this paper. The ceramic coating was analysed by X-ray, SEM arid TEM. The forming process of the ceramic coating was discussed and the possible forming mechanism of the ceramic coating was brought forward. The corrosion resistance, the wear resistance, the hardness and the porosity of the ceramic coatings were measured and the corrosion resistance of the ceramic coating in the NaCI electrolyte was analyzed.The results studied show that the hot-dipping technologic parameters fitting for micro-arc oxidation are as follows: the hot-dipping time is 2 minutes and the hot-dipping temperature is 710?0 慍; There is a maximal value in the curve that the overall thickness and the thickness grown outward of the ceramic coating changed with the intensifying time. In the time before the thickness of the ceramic coating was the maximum value, the thickness mentioned above increase with the increment of the current density and the ceramic thickness grown inward increase with the prolonging of the intensifying time and the increment of the current density; In our experiment conditions. the maximal thickness of the ceramic coating obtained is about 47 ii m. the corresponding intensifying time is 12 minutes or so and the current density is 1 .5Aidm2: The proportion of the ceramic coating grown inward and outward is influenced by the current density and the intensifying time at the same time. The growing direction of the ceramic coating changed from inward mainly to outward mainly by and by with the increment of the current density; There are molten phenomenon on the surface of the ceramic coating and the pore and the crack in the ceramic coating. The ceramic coating is mainly composed of K-Al,03 and 0 -A1203?and there are a bit of non-crystal A1203 and ~ -Al203. The combination between the ceramic coating and the hot-dipping aluminum coating, the hot- dipping alum~~ coating?1?and the substrate is metallurgical. The corrosion resistance of the micro-arc oxidation samples is far better than the hot-dipping aluminum samples and the Q235 steel in the NaCI electrolyte and the sea water. The hardness of the ceramic coating is HVT300 and the wear resistance of the ceramic is better than the healed 45~ steel. The wear resistance is more than 3 times of the healed 45# steel \\hen the wear distance is 70 meters. There are 239 pores per square centimeter.