基体偏压对316L不锈钢表面多层Ti-DLC薄膜摩擦及腐蚀行为的影响

Effects of Substrate Bias Voltage on Friction and Corrosion Behavior of Multilayer Ti-DLC Film on the Surface of 316L Stainless Steel

在严苛海洋环境下,传统单一的Ti掺杂类金刚石薄膜(DLC)无法满足减摩耐磨及耐腐蚀性能的要求,仍须进一步探索.为促进DLC薄膜在严苛海洋环境下的应用,采用中频磁控溅射技术在316L不锈钢上制备Ti/TiN/TiCN/Ti-DLC复合薄膜.通过SEM、拉曼光谱、XPS、纳米压痕测试、摩擦磨损试验及电化学测试等方法,重点研究基体偏压对薄膜结构、力学性能、摩擦性能及耐腐蚀性能的影响规律.结果显示:随着基体偏压从-60 V到-120 V,薄膜中sp3-C/sp2-C比值逐渐增大,薄膜硬度及弹性模量逐渐增大;薄膜结合力呈现先增大后减小的趋势,在-80 V时达到最大24.5 N;在7N的法向载荷下,薄膜磨损失效时间先增大后减小,偏压为-80 V时磨损寿命最长;316L不锈钢和所有薄膜的阳极极化曲线都表现出明显的钝化现象,在偏压为-120 V时,薄膜的维钝电流密度比316L不锈钢低两个数量级,表现出优异的耐蚀性;薄膜电阻Rf和电荷转移电阻Rct逐渐增大,薄膜的耐腐蚀性能逐渐增强.Ti/TiN/TiCN/Ti-DLC复合薄膜的多层结构和元素掺杂相结合的设计有效提高了316L不锈钢的耐腐蚀性能和减摩耐磨性能,拓宽了类金刚石薄膜在严苛海洋服役环境下的应用范围.

Diamond-like carbon(DLC)films are widely used in the fields of aerospace,metal processing,and marine protection because of their high hardness and excellent wear and corrosion resistance properties.Among them,Ti-doped DLC films have a wide range of applications in the field of surface protection.However,conventional single Ti-doped DLC films are unable to meet the wear and corrosion resistance requirements of harsh marine environments.Thus,the preparation process must be further explored.To promote the application of DLC films in harsh marine environments,Ti/TiN/TiCN/Ti-DLC composite films were prepared on 316 L stainless steel using the medium-frequency magnetron sputtering technique.Scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS)were applied to analyze the microscopic morphology,corrosion morphology,and elemental content of the films.The bonding state and chemical composition of the films were analyzed by X-ray photoelectron spectroscopy(XPS).The hardness,tribological behavior,and corrosion resistance of the films were evaluated by a nanoindentation tester,friction and wear tester,and electrochemical testing.The experimental variables are the negative bias voltages of the matrix(-60 V,-80 V,-100 V,and-120 V).The influence of the substrate bias on the structure,mechanical properties,friction properties,and corrosion resistance of the films is highlighted.The results show that the Ti element in the Ti-DLC section mainly exists in the form of TiO2,TiC,and TiCN.The overall thickness of the films deposited at the four different bias voltages is approximately 2μm.The thickness of the Ti-DLC section is stabilized in this range of 0.82±0.03μm,which indicates that changes in the substrate bias voltage have lttle influence on the growth rate of the films.The atomic fraction of the Ti element in the surface layer of allfilms is approximately 5%,indicating that the change in the substrate bias voltage has little effect on the chemical composition of the film surface.As the substrate bias voltage increased from-60 V to-120 V,the sp-C/sp2-C ratio,hardness,and elastic modulus also gradually increased.The adhesive force of the films tended to first increase and then decrease,reaching a maximum of 24.5 N at-80 V.Under a normal load of 2 N,the friction factor of all films ranged from 0.24 to 0.32,which is less than that of 316 L stainless steel(0.8).This indicates that the films play a key role in the antifriction and wear resistance.Under a normal load of 7 N,the wear life of the films first increased and then decreased.The wear life was the longest at a bias voltage of-80 V.The anodic polarization curves of 316 L stainless steel and all the films exhibited an obvious passivation phenomenon.The current density to maintain the film passivity is two orders of magnitude lower than that of 316 L stainless steel at-120 V,which shows excellent corrosion resistance.The film resistance Rr and charge transfer resistance Ret gradually increased,indicating that the corrosion resistance of the films gradually improved.The corrosion morphology shows that the main corrosion mechanism of all the films is pitting corrosion.These results show that the design of Ti/TiN/TiCN/Ti-DLC composite films with a combined multilayer structure and Ti-element doping improved the wear resistance and corrosion resistance of 316 L stainless steel and broadened the scope of application of DLC films in marine service environments.