AlxHfMoNbZrN薄膜的晶体结构、力学性能和腐蚀行为研究

Crystallographic Structure,Mechanical Property and Corrosion Resistance of Al,HfMoNbZrN High Entropy Nitride Thin Films

探究Al元素含量对AlxHfMoNbZrN高熵难熔薄膜晶体结构、硬度、摩擦磨损性能和耐腐蚀性能的影响。使用直流反应磁控溅射分别在Si(001)、Al_(2)O_(3)(0001)和硬质合金(WC-8wt.%Co)基体表面制备不同Al含量的AlxHfMoNbZrN薄膜。选用扫描电子显微镜(SEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)分别对薄膜的断口形貌、成分和晶体结构进行表征。利用纳米压痕仪、摩擦磨损试验仪、三电极体系的电化学工作站分析薄膜的硬度、耐磨性和耐腐蚀性能。薄膜均为NaCl型面心立方单相固溶体结构,随着Al元素含量增加,薄膜结晶性增强,厚度增加。垂直于基体表面方向,200峰对应的微晶尺寸先减小后增加。当Al靶功率为30W时,薄膜硬度最高可达24.7GPa±0.83GPa。薄膜与Si_(3)N_(4)对偶球的摩擦因数保持在0.6~0.8之间,其中HfMoNbZrN薄膜的磨损率最低,为9.93×10^(-15)m^(3)/(N·m),然而,与添加Al元素的薄膜相比,HfMoNbZrN薄膜发生更严重的氧化磨损。添加Al元素后的薄膜较HfMoNbZrN薄膜耐蚀性均有提升,Al元素可有效提高AlxHfMoNbZrN薄膜的硬度、耐腐蚀性以及降低薄膜的氧化磨损,可根据应用场景决定AlxHfMoNbZrN薄膜中Al元素的成分配比。

This work aims to investigate the effect of Al elemental concentration on AlxHfMoNbZrN thin films in terms of crystal structure,hardness,tribological and corrosive behavior.AlxHfMoNbZrN thin films are grown on Si(001),Al_(2)O_(3)(0001)and cemented carbide(WC-8wt.%Co)substrates using Hf(25)Mo(25)Nb(25)Zr(25)and Al targets powered by direct current(DC)reactive magnetron sputtering.The varied Al content in the as-deposited thin films is achieved by changing the discharge power of Al while keeping the Hf(25)Mo(25)Nb(25)Zr(25)target power stable.The elemental composition,crystal structure and cross-sectional morphology of the thin films are characterized using X-ray energy spectrometry(EDS),X-ray diffractometry(XRD)and scanning electron microscopy(SEM).The hardness,tribology behavior and corrosion performances of the thin films are respectively determined by using nanoindenter,tribometer and electrochemical workstation with a three-electrode system.The results show that the element concentration of Al increases from 0at.%to 6.7at.%by increasing Al target power from 0W to 60W and the content of O element decreases from 11.2at.%to 5.6at.%.In addition,when P(Al)30W,the O element content decreases from 6.9at.%to 5.6at.%.All thin films exhibit a NaCl-type FCC singlea-phase structure with the increases of Al target power,the thin film crystallinity and thin film thickness increase,accompanied by a decrease and then increase of out-of-plane crystallite size estimated from the 200 diffraction peak.The highest hardness is obtained by the Al target power of 30W case,where H=24.7GPa±0.83GPa is achieved.The trends for H/E and H^(3)/E^(*2)are essentially the same as for hardness,with the highest value at P(Al)=30W of 0.086±0.004 and 0.151GPa±0.017 GPa respectively.The coefficients of friction of the thin films against Si3N4 counterpart range from 0.6 to 0.8.The wear rate of the thin films decreases with the Al content increases,and the lowest wear rate,9.93×10^(-15)m^(3)/(N·m),is obtained by HfMoNbZrN,yet severe abrasive wear is observed as compared to Al-containing thin films indicating an increasing anti-oxidative wear feature of AlxHfMoNbZrN thin films.Al-containing thin films show better corrosion resistance in an aqueous NaCl solution with a mass fraction of 3.5%as proved by a combination of results from potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS)plots.AlxHfMoNbZrN thin films show advanced performance in hardness,anti-oxidative wear and anti-corrosion as compared to the HfMoNbZrN thin film,and thus holds great potential in applications as protective coatings.