The study aims at investigating the effect of auxiliary preparative and closing implantations in hardened tool steels on surface tribology modification. Samples of a martensitic tool steel. SKD 11, are triply implanted with ions of N or Ar at higher energies, N at the normal energy, and N, BF and CO₂ at lower energies. The ion implantations result in dramatic increases of hardness and wear resistance to the samples in comparision with singles N-ion implantation and double ion implantation. Analysis of ion depth profiles and surface compositions and microstructures is performed to reveal the mechanisms. It can be concluded that the improvement of the mechanical properties can be attributed to the deepening in the ion penetration and the forming of compound covers at the surface region. ã 1999 Elsevier Science B. V. All rights reserved.