Impact test and tribological behaviour of duplex-treated low-alloy steel

The aim of this work was the evaluation of the improvement of mechanical properties of a low-alloyed steel using a duplex treatment (nitriding + CrN 5 μm PVD). The effect on adhesion, wear, impact resistance and stiffness was investigated. The obtained results were compared to CrN coating deposed on traditional quenching and tempering substrate, heat treatment at which a 4140 steel grade is usually processed. The microstructure was analyzed by scanning electron microscopy and the mechanical properties were evaluated by nanoindentation testing, impact resistance evaluation, scratch resistance measurements and ball-on-ring wear testing under unlubricated conditions. The results showed an improved critical load, better tribological properties (friction coefficient equal to 0.1 during the wear test) and an increased behaviour in the presence of cycling impact loading conditions (up to a normal applied load of 5 GPa) for the duplex-treated samples. Therefore for functional coated components an extension of duplex-treated low-alloyed steels is expected.