Preparation and properties of electrospark coatings from Ti3Al granules with silicon carbide and boron carbide additives

摘要

The composite coatings Ti-Al, Ti-Al-Si-C and Ti-Al-B-C were formed on the Ti6Al4V titanium alloy by a new method of electro-spark deposition from granules. The granules were produced by sintering powders of titanium and aluminum mixed in a ratio of 3?:1, including 15?wt.% additives of silicon carbide and boron carbide. During coating, the frequency of the discharge pulses was 1?kHz, the on-pulse duration was 0.1?ms, and the deposition time was 12?min. The manufactured electro-spark coatings had a thickness of 20-40?μm. The composition of the surface layer formed by the deposition of pure intermetallic Ti3Al coincides with the composition of the initial material of the electrode. The Ti-Al-Si-C coatings are based on TiC, Ti5Si3 and Ti1+xAl1-x. The electrospark coatings formed from Ti-Al-B-C granules contain intermetallic compound Ti3Al, borides TiB and TiB2. Among the investigated samples, the Ti3Al?+15%SiC coating has the highest microhardness, which is approximately 4?times higher than that of the titanium substrate from Ti6Al4V. The wear intensity of the titanium alloy during dry friction decreases by more than 19 times if it is coated with Ti3Al or Ti3Al?+15%B4C coatings. The coating deposited from Ti3Al granules with 15?wt.% SiC additive has the highest wear resistance, its rate of deterioration is 38?times lower compared to Ti6Al4V. The friction coefficient of the obtained composite coatings is equal to 0.38?–?0.52. The oxidation rate of the titanium alloy during the isothermal heating at a temperature of 900°C can be reduced by 1.9?times if the alloy is coated with Ti3Al, and can be reduced by 2.3?times if the alloy is coated with Ti3Al with the additions of SiC or B4C.