Study on the Microstructure and Cutting Process of CrN-Coated Tools with Different Bias Voltage

CrN coatings prepared by physical vapor deposition may fail prematurely in localized regions during machining due to stress and high temperature. To address this problem, three groups of CrN coatings with different bias voltages were deposited on cemented carbide tools using cathodic arc ion plating. The influence of coating microstructure on cutting performance was investigated. The surface and cross-sectional morphologies of the coatings were observed using scanning electron microscopy. The crystal structures of the coatings were characterized using X-ray diffraction. The nanohardness values and elastic moduli of the coatings were measured using nanoindentation, and the coating–substrate adhesion was evaluated using a scratch tester. The residual stresses of the coatings were determined using the substrate bending method. The cutting performance of the coated tool was tested using a Computer Numerical Control (CNC) machine tool. The cutting process using coated tools was simulated using ABAQUS 6.14 software. The results indicated that, as the bias voltage increased, the droplets on the surface of the CrN coating became smaller and the structure became denser, but the thickness gradually decreased. The hardness increased from 18.59 GPa at 100 V to 24.57 GPa at 200 V, the bonding force increased from 72.6 N to 78.5 N, and the residual stress also increased to −2.22 GPa. Cutting tests showed that the cutting performance of the 200V-CrN coating was nearly twice that of the 100V-CrN coating. According to the microstructure and finite element simulation results after cutting, the 200V-CrN coating with a dense structure and higher residual compressive stress exhibited better stress-absorption capacity and was less susceptible to wear or fracture during the cutting process, thereby extending tool life.