Using Fe–3·5%Mo (MSP 3·5Mo) prealloyed powders, various steels were manufactured with 0·7% carbon addition but different contents of copper and nickel. All the steels were compacted at 700 MPa and sintered in a N₂–H₂ atmosphere at 1150°C. After being sintered, the materials were thermochemically treated by means of plasma nitriding and gas nitriding. The mechanical properties evaluated were: tensile and yield strengths, elongation, hardness, microhardness, and wear resistance against two reference materials (steel and alumina). A complete metallographic study was carried out using optical and scanning electron microscopy. Properties of the materials following the two thermochemical treatments were compared, and the relationship of properties to the microstructure was analysed. Nickel and copper improve the mechanical properties in the sintered state and after thermochemical treatment. Plasma nitriding enhances the mechanical properties and wear resistance.