QUASICRYSTAL ABRASIVE POLISHING ON SOFT METALS VIA A CHARACTERISTIC SMEARING WEAR MECHANISM FOR EFFICIENT SURFACE FLATTENING, HARDENING AND CORROSION ENHANCEMENT

Polishing soft metals using hard abrasives such as diamond, alumina, and silica can easily damage the worn surface by deep scratches and by large material removal due to cutting wear mechanism. An abrasive material with appropriate hardness, hardness/elasticity ratio, and low friction is then highly desirable, which would avoid intense abrasion while at the same time minimize scratching on soft metals. Quasicrystals are characterized by low friction and high hardness/elasticity ratio, making them potentially suitable for use as abrasives for soft metals. It has been pointed out by the authors that AlCuFe quasicrystal abrasive shows a particular smearing dominant wear mechanism and can be used as a special abrasive for flattening soft metals. In this work, the Al62Cu25.5Fe12.5 quasicrystal abrasive was chosen, to compare with conventional hard abrasives such as diamond, alumina and silica, to wear against copper, 2024 aluminum alloy and 304 stainless steel. The surface topography, nano-indentation hardness, smearing coefficient, mass loss and electrochemical impedance were measured and the results indicate that the surface flattening is influenced by the smearing coefficient, a parameter developed to assess the degree of smearing-type wearing. A larger smearing coefficient leads to a more flatten surface at the least expense of mass loss. It is specially noticed that the characteristic smearing mechanism of quasicrystal abrasive produces an obvious surface hardening effect, with the nano-hardness of 304 stainless steel being increased by about 0.3 GPa. The corrosion resistance of the Al alloy is also enhanced due to the formation of a thick and dense passive film.