Improvement of wear resistance of aluminum alloy by HVOF method

Abstract

This work is devoted to establishing the effect of High Velocity Oxygen-Fuel (HVOF) method for spraying coatings with vanadium carbide (VC) (as an alternative to galvanic chromium plating) on the wear resistance of obtained coatings in friction conditions with a rigidly fixed and non-fixed abrasive. The initial components for spraying coatings were powders of VC, ferrochrome (FeCr) and cobalt (Co). The powder compositions of the two (FeCr – VC) and (FeCr – VC – Co) systems were deposited on to a substrate of an aluminum alloy 7075. Each of compositions was mixed in a planetary mill for the mechanical alloying. A thickness of obtained coatings was 200 μm. It was discovered that (FeCr – VC) and (FeCr – VC – Co) coatings, obtained by the HVOF method with using of both gaseous (propane - oxygen) and liquid (kerosene – oxygen) fuels, have high wear resistance. The wear resistance of the coatings with using of friction method with rigidly bonded abrasive increases with the size of the VC carbide inclusions. In the presence of cobalt in the coating, the trend is similar, but its wear is bigger. Since cobalt does not form carbides, in the structure of such coating forms ductile inclusions based on it. As a result of the friction test using non-fixed abrasive, the wear resistance of coatings increased with decreasing VC carbide size in their structure and increased at addition of cobalt powder to powder composition for spraying.