Study Of Micro-arc Oxidation Technology And Ceramic Coating Forming Mechanism

Utilizing20kW high power micro-arc oxidation equipment designed and manufactured by ourselves laboratory, this thesis had studied the impact mechanisms of many influential factors on the forming behavior, thickness, surface hardness, surface and cross-section morphology, microscopic phase composition of oxide ceramic coatings for Al alloys and Ti alloys. Based on these results, the effects of anodic/cathodic currents ratio and single pulse discharge energy both on the mechanism of micro-arc oxidation and on the properties of oxide ceramic coatings on the surface of Al alloy and Ti alby have been studied. For Al alloy and Ti alloy, the spark breakdown mechanism of micro-arc oxidation and the forming behavior of oxide ceramic coatings are very much the same, so the process parameters have the same effect trend on the forming behavior and properties of the oxide ceramic coatings. This paper has analyzed the effects of anodic/cathodic currents ratio on the properties of oxide ceramic coatings on Al alloy and the influence laws of single pulse energy on the properties of oxide ceramic coatings on Tialloy respectively.Experimental results show that:1. The coatings surface roughness Ra, H and Hout decrease with the decreases of the anodic/cathodic current ratio while Hin, the hardness and the proportion of dense layer increase; But once the anodic/cathodic current ratio is too small, there is pitting corrosion phenomena on the oxide ceramic coating surface easily, so the corrosion resistance and the overall performance of ceramic coating be destroyed.2. The size of single pulse energy determines the properties of oxide ceramic coating; The surface roughness, the growth rate and the hardness of oxide ceramic coating increase with the increasing of the single pulse energy, and the micro hardness of oxide ceramic coating increases and then decreases with the increasing of the single pulse energy.3. In the micro-arc oxidation process of titanium alloy, we put forward the parameter design guiding ideology "smaller pulse width, and higher pulse". In order to balance the forming layer efficiency and the oxide ceramic coating properties, we put forward the optimization principles of the process parameters for the process of titanium alloy micro-arc oxidation "smaller duty ratio, lower pulse frequency".