Study On Silica Films For Improving Oxidation Resistance Property Of 45 Steel

According to the advantages of silica, such as corrosion resistance, good chemical stability, good mechanical strength, this paper studies the silica films made in sol-gel to improve the oxidation resistance of 45 steel and prolong the application.Tetraethyl orthosilicate is used as the prodromal hydrolytic substance, ethanol is used as the solvent, ammonia or hydrochloride is used as the catalyst, the experiments have prepared the silica sol by mensurating the Tyndall effect of different liquid and got the even, complete and compact silica film having good adhesion on the surface of 45 steel.In order to getting the complete and compact silica film having good adhesion on the surface of 45 steel, the experiments have determined the parameters of coating by cross cut test: the best layer number of films is three, the best pulling rate is 3mm/s, and the roasting temperature is 600℃. For improving the adhesion between the films and the surfaces of steel, an interlayer which is film. The silica sol which was made by base catalysis is coated on the surfaces according to the properties of Fe₃O₄. Then the silica sol which was made by acid catalysis is coated on the surfaces. The results were found in experiments: the improving effect of the silica films that the first layer was made by base catalysis and the last two layers were made by acid catalysis ("1+2" layers silica films) is better than the silica films having three layers films which were made by base catalysis ("3+0" layers silica film). In this paper, the 45 steel samples which have "1+2" layers silica films on their surfaces were roasted in 650℃,700℃,750℃,800℃for 1.5h. And an oxidation kinetic curve has been gotten in the experiment. The results found on the oxidation kinetic curve is that the silica films have good improving effect for 45 steel in 650℃,700℃,750℃, but there is not improving effect in 800℃for 1.5h because of cracking and exfoliation phenomena.The films made in paper have good adhesion, compactness, long life, and can be gotten on different metal materials which open up more extensive the application space.