Comparative evaluation of ambient temperature friction behaviour of thermal sprayed Cr3C2–25(Ni20Cr) coatings with conventional and nano-crystalline grains

Due to their improved hardness and toughness properties, nano-crystalline materials have become attractive for a wide variety of applications. However, as the processing of nano-crystalline materials is quite expensive, efforts have been made to develop coatings using nano-crystalline grains. The present study investigates the ambient temperature friction behaviour of Cr3C2–25(Ni20Cr) coatings with nano-crystalline grains (CNG). In the technical process, both, Cr3C2–25(Ni20Cr) coatings with conventional grains (CCG), and nano-crystalline grains were deposited using an HVOF technique. Micro-structural characteristics and mechanical properties of the coatings were determined. Friction behaviour of the coatings as a function of different test conditions was evaluated. The specimens worn were examined by a scanning electron microscope (SEM). The results showed that the coefficient of friction of the CNG against 100Cr6 steel is lower than that of CCG against 100Cr6 steel. The principal types of material removal of CNG on the one hand, and CCG on the other, differ. Maps showing the prevalence of different wear mechanisms for different wear conditions were established for both types of coatings.