沉积偏压对MoN涂层结构和柴油中摩擦学性能的影响

Effect of Deposition Bias Voltage on Structure of MoN Coating and Tribological Properties in Diesel

目的研究沉积偏压对MoN涂层微观结构、性能,以及在柴油介质中摩擦学行为的影响机制。方法采用磁控溅射技术在304不锈钢基体上沉积MoN涂层。利用X射线衍射仪、X射线光电子能谱仪、X射线能谱仪、原子力显微镜、纳米压痕仪、薄膜应力测试仪和电化学工作站研究MoN涂层的微观结构、成分、表面粗糙度、力学性能、耐腐蚀性能。利用球-盘式摩擦实验机和激光拉曼光谱仪对MoN涂层在0号柴油中的摩擦学行为及机制进行研究。结果随着偏压的增加,涂层的厚度和膜-基结合力均呈先增大后减小的趋势;涂层的表面粗糙度、内应力和硬度呈先升高后降低的趋势。在偏压为-120 V时,沉积的γ-Mo2N涂层组织致密、表面光滑(Sa 7.78 nm)、硬度高(18.02 GPa)、膜-基结合力高(253 m N)。随着偏压的增加,涂层的摩擦因数呈先减小后增加的趋势。在偏压为-120 V时,沉积的γ-Mo_(2)N涂层的摩擦因数和磨损率均最小,分别为0.10和1.8×10^(-7)mm^(3)/(N·m)。拉曼光谱分析结果表明,在摩擦催化作用下,柴油在磨痕表面产生了碳基膜。此外,通过电化学腐蚀分析发现,在偏压-120V下沉积的γ-Mo_(2)N涂层具有优异的耐腐蚀性能。结论MoN涂层结构、性能受到偏压的影响显著。柴油在摩擦催化作用下发生了降解,形成了碳基膜,这有利于降低MoN涂层的摩擦因数和磨损率。

This article aims to investigate the effects of deposition bias voltage on the microstructure of MoN coatings and its tribological behavior in diesel.MoN coatings were deposited through magnetron sputtering on the 304 stainless substrate by adjusting the deposition bias voltage(−50-−200 V).The crystal structure,elementary composition,surface roughness,hardness,film-substrate bonding force,internal stress,corrosion resistance,and other properties of MoN coatings were detected by an X-Ray diffractometer,an X-ray photoelectron spectroscopy,an X-ray energy spectrometer,an atomic force microscopy,a nanoindenter,a film stress testing apparatus,and an electrochemical workstation.The tribological behavior of MoN coatings in 0#diesel was detected by a tribometer in ball-on-disk type,and the morphology of the worn surface of MoN coatings was examined on a Laser Raman spectrometer and an SEM.According to the results,the phase structure of MoN coatings was B1-MoN when the bias voltage was−50 V.When the bias voltage was increased to−80 V,the phase structure of MoN coatings changed from B1-MoN toγ-Mo_(2)N.When the bias voltage was further increased to−200 V,the phase structure of these coatings was found to remain the same.With the increase of the deposition bias voltage,the ion sputtering effect was enhanced,the Mo content increased and the N content decreased,the surface roughness,nano-hardness and internal stress of the films first decreased and then increased,and the thickness of the coatings and the film-substrate bonding force first increased and then decreased.When the deposition bias voltage was−50 V,the deposited MoN coating had a loose structure,rough surface,low hardness(14.96 GPa),high internal stress,poor film-substrate bonding and poor corrosion resistance.When the deposition bias voltage was higher than−80 V,increasing the deposition bias voltage was accompanied by increasing the structural compactness of the coating.The surface roughness decreased from 8.38 nm to 7.78 nm and then increased to 8.59 nm.The hardness was high(18.02 GPa)and the binding force of film and substrate was high(253 mN).The internal stress increased from 0.13 GPa to 0.29 GPa.The nano-hardness increased from 14.72 GPa to 19.55 GPa.The film-substrate adhesion decreased from 263 mN to 241 mN.The tribological behavior of the MoN coating in diesel was tested and found that when the bias voltage was−50 V,the coating peeled off during the test and the friction coefficient and wear rate showed high values of 0.16 and 5.48×10^(−6)mm^(3)/(N·m),respectively.At a bias voltage of−120 V,the coating was found to have the best tribological behavior with a lower coefficient of friction and wear rate(0.1 and 1.8×10^(−7)mm^(3)/(N·m)).Furthermore,Raman and SEM analyses showed that the wear scars of the coatings were covered by carbon-based films.This was because,during the friction process,the diesel fuel was degraded into a carbon-based film due to the catalytic effect of MoN and friction,which served to protect the coating to reduce friction and wear.The structure and properties of MoN coating are affected by the bias voltage,while theγ-Mo2N coating has the best mechanical and tribological properties and high corrosion resistance.In diesel oil,friction catalysis makes diesel oil degrade to form a carbon-based film,which is beneficial to reduce the friction coefficient and wear rate of MoN coating.