The effect of ion implantation in high speed steel ASP 23 on chemical vapour deposition (CVD) diamond nucleation has been studied. N, C and Si have been implanted at 100–150 keV and fluences in the range from 5×10 17 to 2×10 18 ions cm −2. Tribological measurements and dry turning tests were carried out to investigate the influence of the ion implantation on the steel. The results are compared with those of untreated high speed steel substrates. The diamond deposition onto the ion beam modified steel substrates was carried out in a microwave plasma CVD apparatus. The substrate temperature was kept below 520 °C, because of the fusing temperature of the steel. By means of scanning electron microscopy, Raman spectroscopy, Auger electron spectroscopy and Rockwell indentation tests, the deposition parameters for the CVD process were optimized. It was found, that the Si implantation was advantageous for the consecutive diamond deposition.