Zadorozhna K. Increasing of the abrasive wear resistance of aluminum alloys by forming coatings strengthened by SiC and VC carbides

The dissertation is devoted to establishing the laws of the surface layers structure formation of aluminium alloys by laser modification with SiC particles and high-speed flame spraying of coatings with the addition of VC, which is proposed as alternative hardening methods compared to galvanic chromium plating. In addition, the wear resis¬tance of strengthened layers by testing using a rigidly fixed and not fixed abrasive, as well as their corrosion-electrochemical properties in aqueous media with pH≈7 were estimated. To obtain wear-resistant Al – SiC composite layers up to 1.5 mm thick the regime of laser modification of the surface by silicon carbide particles was optimized in the range of 740...1100 J/cm of the linear energy input. Based on the complex of studies, the influence of both the sizes of vanadium carbides and the presence of cobalt inside the strengthened layers obtained by high-speed flame spraying on the wear resistance and a wear mechanism under various test conditions were established. The methods of surface hardening of B95 aluminium alloy were ranged relative to unstrengthened alloy by the wear resistance level under various test conditions, as well as their energy consumption and environmental safety. It is revealed that to increase the wear resistance at testing with fixed abrasive, environmentally friendly laser modification of the alloy surface by SiC particles is more effective than galvanic chrome plating. At its using the wear resistance of the strengthened layers increases by 93 times relative to non-modifications alloy. At wear testing with a not fixed abrasive, the coating using high-speed flame spraying by the VC particles was more efficiently increased the wear resistance of an aluminium alloy (up to 7–9 times). Keywords: aluminium alloys, laser-modified layers, silicon carbide, linear energy input, high-speed flame coatings, vanadium carbide, cobalt inclusions, wear resistance, rigidly fixed abrasive, not fixed abrasive, corrosion resistance.