Study on the structure and tribological properties of CrN coating by IBED

Abstract CrN coatings were synthesized with different levels of bombarding energy by nitrogen ions with very low N ion/Cr atom arrival ratios. The structures and compositions of these coatings were investigated by XRD, XPS and AES. The tribological properties of the coatings on AISI 52 100 steel were evaluated by ball-on-disc tests. Results indicate that the fraction of the CrN phase increases with increasing bombarding energy from 4 to 8 to 12 keV, and reaches a predominant state. For the 4 keV coating, the Cr/N ratio was >1, which indicates that Cr is involved in the coating layer. The 8 and 12 keV coatings were free of Cr phase. However, the optimum N ion/Cr atom ratio for the coating is far from the stoichiometry of 1:1 Cr/N. The tribological properties of CrN coatings with different processing parameters show that the wear mechanisms of coating/substrate systems are micro-ploughing and spalling. The films processed at a low energy level and with a low N ion/C atom ratio in this study show better tribological properties and higher fracture toughness.