Plasma immersion (PI3) ion implantation of AISI M2 steel by nitrogen was carried out. The implantation voltage was 40 kV and the doses varied in the range of 2-8 x 10(18) ions/cm(2). It is established that the hardness of steel increases up to 25 GPa, the friction coefficient decreases by the factor of 2 and wear resistance is enhanced by a factor of 10 after PI3. It is explained by the formation of a highly doped face-centered-cubic gamma-Fe(N,C) phase that is due to local tempering of the steel surface. The total concentration of nitrogen and carbon in this;phase is about 40 at. %.