Study On Ceramic Surface Coating Process Of AFA 3G Fuel Rod

This paper presents an investigation report on ceramic surface coating processes on Zircalloy, it includs Anodic Oxidation(ANO), Microarc Oxidation(MAO) and High Frequency Induction Oxidation(HFIO). In this paper, the film properties and effect factors of the three ceramic coating processes are analysed.The results show that the thickness of anodic oxidation film grow up with the voltage rising, and there is a linear relation between them; The oxidation film obtained from NaOH solution gets the best properties: smoother surface, less porosity and cracks; the main composition of the film are ZrO₂ and SnO₂, and the ZrO₂ is more than 90%.MAO(Microarc Oxidation) is the way to make a ceramic film on the zircalloy surface by the actions of thermochemistry, plasmachemistry and electrochemistry. The thickness of MAO film on the surface of Zircalloy can be more than 60μm, with a linear relation between the thickness and the concentration of solution. Three quarter of the film is loosen layer, one quarter is compact.Based on the principle of alternate electromagnetic field, we put a specimen of Zr pipe on the center of a induction coil, and bring into a high frequency induction current. The specimen temperature will rapidly rise to a needed level. At the same time, we bring the special gas into the treating chamber and make the oxidation reaction with the surface of Zr pipe after a time. A excellent ZrO₂ ceramic film will be formed on the surface of zircalloy pipe. There are four kinds of treating gas, and results show that the four kinds of treating gas is suitable for the process. But the atomic oxygen is better than others. Test also shows that the treating temperature is in the range of 530⁶00℃ and the suitable treating time is 3²0min.Compared of 3 techniques, the equipment of the high frequency induction oxidation is simpler than the others, and is easy to run in automatic control. The properties of ceramic layer obtained by high frequency induction oxidation are also better than the others. So the high frequency induction is more suitable for our chosen.