WU Meiling, FENG Yi, JIANG Qili, CHE Zhiqiang, DU Yukang, YANG Longgang, LANG Xiaoyue, WANG Kesheng, OU Yixiang
In order to systematically explore the regulation law of substrate bias on the structure and performance of Cr/CrN/WC composite coatings prepared by high-power pulsed magnetron sputtering (HiPIMS)，Cr/CrN/WC composite coatings were deposited on AISI 304 stainless steel substrates by high-power pulsed magnetron sputtering， and the influence of substrate bias voltage (0 to -300 V) on the structure， mechanical and tribological properties of coatings was investigated systematically.X-ray diffraction (XRD) and scanning electron microscopy(SEM) characterization revealed that as the bias voltage increased to -200 V， the β-WC1-x(200) crystal plane exhibited enhanced preferred orientation， along with refined grains， weakened columnar structure， and significantly improved density.However， at the bias voltage increased to -300 V，excessive ion bombardment induced lattice defects，causing a decrease in density.Mechanical property tests indicated that the coating deposited at -200 V achieved a synergistic enhancement of strength and toughness， exhibiting peak nanohardness (43.25 GPa) and effective Young’s modulus (474.77 GPa).The hardness/modulus ratio (H/E*＝0.091) and plastic deformation resistance parameter (H3/E*2 ＝0.359 GPa) increased by 19.7%and 91.0%， respectively， compared to the 0 V sample.In addition， Rockwell C indentation tests further confirmed that the coating's adhesion strength achieved grade HF1 (optimum)， with no crack formation or delamination observed around the indent， which was attributed to the high elastic strain coordination of the high H/E* ratio and the high interfacial stress suppression of the high H3/E*2 value.Tribological test results demonstrated that the coating deposited at the bias voltage of -200 V exhibited the lowest coefficient of friction (0.42) and the minimum wear rate [1.39 × 10-7 mm3/(N·m)]，owing to the high hardness and low surface roughness，and the wear mechanism was mild oxidative-adhesive wear.In contrast， the coatings deposited at 0 V and -300 V showed higher wear rates [2.78 × 10-7 mm3/(N·m) and 1.85×10-7 mm3/(N·m)]， and their wear mechanisms were abrasive-oxidative composite wear and soft phase-induced abrasive wear， respectively.In summary， the -200 V bias voltage achieved quaternary synergistic optimization of hardness， toughness， adhesion strength and wear resistance through the grain refinement and structural densification， while the excessive bias voltage (-300 V) led to coating performance degradation due to lattice damage and interfacial weakening.
