Deposition and characterisation of Mo2N/CrN multilayer coatings prepared by cathodic arc evaporation

This paper presents the evaluation of the surface quality and properties of Mo2N/CrN multilayer coating, compared to Mo2N and CrN coatings, deposited onto HS6-5-2 steel substrates using pure Mo and Cr targets in a nitrogen atmosphere by cathodic arc evaporation. The coatings were investigated by X-ray diffraction to evaluate the phase composition, scanning electron microscopy and optical microscopy to calculate the surface density of macroparticles of the coating and their dimensions. Hardness, friction, wear and adhesion of the coatings using the scratch test and Daimler-Benz test were also estimated. The Mo2N/CrN coating shows hardness above 25 GPa and good adhesion with the critical load Lc2 about 60. The coefficient of friction of coatings studied is relatively low, 0.51 (CrN) and 0.44 (Mo2N). The Mo2N/CrN multilayer coating shows the lowest coefficient of friction of 0.40. A similar correlation holds for wear the highest wear rate in the test conditions is for a CrN coating-about 5.7 x 10(-7) mm(3)N(-1)m(-1) for Mo2N about three times lower, and the multilayer coating Mo2N/CrN 9 x 10(-8) min(3)N(-1)m(-1). Despite the relatively low critical load, investigated coatings show excellent wear resistant properties. This work is part of the research on nanocomposite hard coatings for tribological applications where molybdenum nitrides are dedicated as a component reducing friction and wear. (C) 2015 Elsevier B.V. All rights reserved.