Gas mixtures in the plasma nitriding, which was performed after the samples were TRD-chromized, have a significant influence on the tribological properties of the duplex treated steels. The lowest friction coefficient was observed for the samples duplex treated in a 50%N2+50%H2 plasma.Thesampleschromizedandduplextreatedineithera 75%N2+25%H2 mixture or a 100% N2 plasma exhibited higher friction coefficients. The samples duplex treated with 50%N2+50%H2 plasma exhibited the best wear resistance, whereas the lowest wear resistance was found for the samples duplex treated in a 75%N2+25%H2 plasma, probably due to formation of a hard and brittle layer. For all surface treated steels, delamination is the principal wear mechanism. During sliding wear testing, the duplex treated steels prepared in a 50%N2+ 50%H2 plasma showed less tendency towards subsurface crack initiation than steel prepared in a 75%N2+25%H2 plasma.