The thickness of the diffusion layers was studied, along with the phases and the microstructure and composition, across the depth in diffusion zone. The obtained results proved the effect of nitriding system in the growth of the diffusion layers on surface of double composite martensitic - austenitic alloy steel. Analysis of mechanical and tribological characteristics of treated double composite steel under dry friction was also studied. It was found that diffusion treatment had a significant influence on work capacity of tested alloy. Stability of alloy after nitriding was (2.5-4) times higher in magnitude compared to untreated alloy.