Effect of Axial Magnetic Field on the Microstructure and Mechanical Properties of CrN Films Deposited by Arc Ion Plating

Abstract

CrN films were deposited on the high-speed-steel substrates by arc ion plating. The effect of an axial magnetic field on the microstructure and mechanical properties was investigated. The chemical composition, microstructure, surface morphology, surface roughness, hardness and film/substrate adhesion of the film were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope (SEM), surface morphology analyzer, Vickers microhardness test and scratch test. The results showed that the magnetic field puts much effect on the microstructure, chemical composition, hardness and film/substrate adhesion of the CrN films. The N content increases and Cr content decreases when the magnetic flux density increases from 0 to 30 mT. All of the CrN films were found to be sub-stoichiometric. With an increase in the magnetic flux density, the film structures change in such way: Cr2N → Cr2N + CrN → CrN + Cr2N → CrN. The SEM results showed that the number of macroparticles (MPs) on the film surface is significantly reduced when the magnetic flux density increases to 10 mT or higher. The surface roughness decreases with the magnetic field, which is attributed to the fewer MPs and sputtered craters on the film surface. The hardness value increases from 2074 HV0.025 at 0 mT (without magnetic field) and reaches a maximum value of 2509 HV0.025 at 10 mT. The further increase in the magnetic flux density leads to a decrease in the film hardness. The critical load of film/substrate adhesion shows a monotonous increase with the increase in magnetic flux density.