Preparation Process And Properties Of TC4 Titanium Alloy Micro-arc Oxidation Black Film

Titanium and its alloys are the main materials for external cameras of spacecraft,so it is especially important to increase the high absorbance and high emissivity of the surface.Titanium alloy black micro-arc oxide film layer can improve the protection performance and matting performance of titanium alloy,So the study of the titanium alloy black micro-arc oxidation film layer is very important.In this paper,a micro-arc oxidation technique was used to prepare a black ceramic film with uniform color on the surface of titanium alloy.The effects of colorant type,concentration and electrical parameters on the corrosion resistance and photoaging of black oxidized ceramic film were studied.The results show that with the extension of the termination voltage and oxidation time,the traces of the melt on the surface of the film increase significantly,the number of discharge holes becomes lesser and the diameter and the surface microcracks becomes larger.The microscopic morphology of the film obtained by adding different colored salts is a typical microporous structure,and uniform microcracks are distributed on the surface of the film.The film layer to which the colored salt Cu salt,Fe salt,and Mn salt are added is mainly composed of an oxide of titanium and an oxide of tungsten,adding different colored salts introduces the corresponding metal compounds.In the micro-arc oxidation process,VO₃^-and WO₄^2-in the electrolyte migrate under the action of an electric field,and are converted into vanadium compound,tungsten oxide and the like at a high temperature to deposit on the surface of the film layer;Fe³⁺,Mn³⁺,and Cu²⁺are present in the form of complexes and uniformly distributed,infiltrating or adsorbing on the surface of the membrane;under high temperature,they enter the molten membrane layer by ion exchange,and correspondingly,iron,manganese and copper are formed in the membrane layer.The vanadate compound,as the micro-arc oxidation reaction progresses,the film thickness increases,the content of the compound in the film layer increases,and the color of the film layer deepens.Electrochemical testing of TC4 alloy black micro-arc oxidation ceramic film layer in3.5wt.%NaCl neutral medium showed that the corrosion resistance of black ceramic film layer was better than that of unadded film layer,black micro-arc oxidation film The layer has good light aging resistance,and the aging time can reach at least 336h before the chromaticaberration occurs.The film layer with Cu salt and Mn salt can even reach 840h.