IMPROVEMENT OF THE MECHANICAL SURFACE-PROPERTIES OF ALUMINUM BY HIGH-DOSE OXYGEN IMPLANTATION

In commercial semi-hard aluminium substrates layers with a high concen tration of very small Al2O3 precipitates were formed by oxygen implant ation in the energy range from 100 keV to 2 MeV. The depth distributio n of the implanted oxygen has been determined by computer simulation a nd Auger depth profiling, The maximum oxygen concentration within the implanted layer covers the range from about 20 to 55 at.%. Auger elect ron spectroscopy is also used in order to prove the oxide formation. T he depth dependence of the relative hardness increase due to the impla ntation has been studied using depth resolving measurements of the dyn amic microhardness. The observed maximum hardness increase varies betw een 1.8 and 3.5 depending on implantation energy and fluence, The wear behaviour has been investigated using a steel ball sliding on the imp lanted aluminium disc with ethanol as lubricant. By an implantation at 100 keV it was possible to avoid adhesive wear and cladding for a loa d of 200 mN. Only for a load of 1.6 N the wear becomes comparable to t he non-implanted state. At higher implantation energies a clear wear t rack is observed like for the non-implanted sample, However, the cross -section area of the wear track is remarkably reduced, e.g. by a facto r 10 after 20 min sliding with a load of 200 mN for 1 x 10(18) O+/cm(2 ) implanted at 200 keV. The optimum wear improvement has been obtained by a three step implantation using the energies 100 keV, 1 MeV and 2 MeV.