Improving oxidation resistance of titanium alloy VT20 by forming composite electrospark Ti3Al + Al/Al2O3 coatings

摘要

Ti3Al intermetallic coatings has been deposited onto titanium alloy VT20 by electrospark deposition method by combination titanium and aluminum electrodes. Synthesis of aluminide Ti3Al occurred in the liquid phase reaction of titanium and aluminum under the influence of low-voltage electrical discharges. In order to improve the oxidation resistance of the obtained composition the thin barrier layer of aluminum or aluminum oxide was deposited. Composite electrode as aluminum tube filled with fine powder Al2O3 was used for electrospark deposition of alumina. The kinetics of the cathode weight gain was studied. Are shown X-ray diffraction data of obtained coatings. The layers thicknesses were from 30 to 70 microns. The coatings roughnesses (Ra) were within 2.2 - 3.5 microns. The kinetics of isothermal oxidation of the obtained samples and uncoated alloy VT20 at 1073 K in air was studied. It was shown that the heat resistance of the coated sample based on Ti3Al is almost two times higher compared to the original alloy. Deposition of an additional barrier layer of alumina onto the Ti3Al coating resulted in lower of speed high temperature gas corrosion as compared to VT20 alloy almost four times. The XRD data of the samples after the corrosion resistance test showed that at the high temperature exposure the surface of the Ti3Al-coated sample of oxidized to alumina and rutile. The composition of the sample with an additional layer of Al2O3 the products of titanium oxidation not been found, that demonstrating the excellent protective properties of the barrier layer deposited.