摘要
本文在AZ91D镁合金表面原位生长微弧氧化陶瓷膜,探究变载荷和位移下微弧氧化(MAO)对AZ91D镁合金微动磨损机制的影响。利用球-平面接触在SRV-V微动摩擦磨损机上探究AZ91D镁合金和MAO膜的微动磨损行为;利用扫描电子显微镜(SEM)分析MAO膜形貌结构和试样磨痕形貌;采用X射线衍射仪(XRD)表征MAO膜相结构;利用激光共聚焦显微镜采集磨痕轮廓和测量磨损体积。结果表明:MAO膜分为多孔疏松层和与基体呈冶金结合的致密层,其均匀性、致密性和结合性良好。随着载荷增加MAO膜的摩擦系数较AZ91D的低,即变载荷工况下MAO膜具有较好的减摩性。变载荷工况下AZ91D磨损机制表现为粘着磨损和剥层;MAO膜磨损机制由粘着磨损转变为磨粒磨损和疲劳剥层。变位移工况下AZ91D磨损机制为粘着磨损和磨粒磨损,伴随有疲劳剥层和氧化;MAO磨损机制由磨粒磨损转变为粘着磨损和疲劳剥层。载荷增加或位移降低时MAO膜的磨损率低于AZ91D的且MAO膜磨痕深度降低,纵深方向的磨损损伤减弱,MAO膜可提高AZ91D镁合金的抗微动磨损性。
Magnesium alloys are widely used in many fields such as aerospace,biomedical and automotive due to their low density,good heat conductivity,great machinability,and high specific strength.However,their low surface hardness and poor wear corrosion resistance lead to severe wear damage,which limit the application range of magnesium alloys.Automotive and aerospace components manufactured from magnesium alloys are prone to cause fretting wear at the mating interfaces in long-term vibration environments.These phenomena significantly increase the probability of premature component failure,thereby diminishing the reliability and safety of these interconnected parts.Surface treatments are used to improve the comprehensive properties of magnesium alloys and enhance their adaptabilities in extreme environments.As a high-efficiency and environment-friendly surface treatment,microarc oxidation(MAO)technique can effectively improve the wear corrosion resistance and broaden the application range of magnesium alloys.MAO technique can form ceramic films on the surface of valve metals such as aluminum,magnesium,titanium,and their alloys.The transient high temperature and pressure are generated by the arc discharge on the metal matrix by regulating the electrolyte ratio and electrical parameters.The sliding friction wear behavior of magnesium alloys before and after microarc oxidation have been mostly studied,but little attention was paid to the fretting wear behavior and mechanism.SRV-V fretting friction and wear testing machine was used to investigate the fretting wear behavior of AZ91D magnesium alloy and MAO film under different normal loads and displacement amplitudes.The contact mode used for the fretting wear experiment was sphere-plane contact.GCr15 ball(Φ10 mm)was selected as the upper specimen and AZ91D magnesium alloy cylinder(Φ24 mm×8 mm)was selected as the lower specimen.MAO film was prepared on the surface of AZ91D magnesium alloy using the home-made microarc oxidation device(MAO-220).The morphological structure of MAO film and the wear morphologies of samples were observed by scanning electron microscope(SEM,QUATA FEG450).The phase structure of MAO film was characterized by X-ray diffractometer(XRD,D/MAX-2400).The confocal laser scanning microscope(OLYMPUS OLS50003D)was employed to capture wear profiles and measure wear volumes.The surface hardness of samples was measured by Vicker microhardness tester(MH-5-VM).The binding force of MAO film was measured by the automatic scratch instrument(Anton Paar RST3).The results showed that MAO film was a dual-layer structure,which is divided into a porous loose layer and a metallurgical dense layer close to the matrix.The thickness of dense layer was 15μm,which accounted for 63%of the total film thickness.MAO film had good uniformity,tightness and binding force,which contained MgO phase,MgAl_(2)O_(4) phase,Mg_(2)SiO_(4) phase and MgF_(2) phase.The friction coefficient of MAO film was lower than that of AZ91Dmagnesium alloy when the normal load increased,but the friction coefficient of MAO film was slightly higher than that of AZ91D magnesium alloy when the displacement amplitude changed.MAO film had outstanding friction reduction capability when the normal load changed,while the effect of displacement amplitude on the friction reduction capability of MAO film was deemed insignificant.MAO film exhibited lower wear rate compared to AZ91D alloy under high normal loads or small displacement amplitudes.This indicated that MAO film possessed superior anti-wear property and provided enhanced protection for AZ91D magnesium alloy.The wear depth of MAO film decreased as the load increases or the displacement amplitude decreased,which could effectively lighten wear damage in the longitudinal direction.The wear mechanism of AZ91D alloy was adhesive wear and fatigue peeling under variable normal loads.As the normal load increased,the wear mechanism of MAO film transited from adhesive wear to abrasive wear and fatigue peeling.As the displacement amplitude increased,the wear mechanism of AZ91D alloy was adhesive wear and abrasive wear,accompanied by fatigue peeling and oxidation.The wear mechanism of MAO film changed from abrasive wear to adhesive wear and fatigue peeling under variable displacement amplitudes.The large accumulation of Fe elements in the wear scars of MAO film indicated that material transfer exited in the fretting wear process and improved the anti-wear resistance and anti-friction performance of MAO film.The large accumulation of O elements in the wear scars of AZ91D alloy indicated that oxidation wear exited in the fretting wear process.The oxygen content in the wear scar slightly decreased as the normal load increased.The frictional dissipation energy coefficient of AZ91D alloy and MAO film decreased with the normal load increased,which could improve the stability of fretting wear process.The normal load and displacement amplitude had a significant effect on the fretting wear behavior of AZ91D magnesium alloy before and after microarc oxidation,which could influence the wear mechanism in the contact area and improve the anti-friction performance and anti-wear resistance of MAO film.
作者
孙璐
李元东
马颖
曹驰
罗晓梅
邱谨
Sun Lu;Li Yuandong;Ma Ying;Cao Chi;Luo Xiaomei;Qiu Jin(School of Materials Science and Engineering,Lanzhou University of Technology,Lanzhou 730050,China;State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals,Lanzhou University of Technology,Lanzhou 730050,China;Wenzhou Pump and Valve Engineering Research Institute,Lanzhou University of Technology,Wenzhou 325000,China)
出处
《稀有金属》
北大核心
2025年第3期317-329,共13页
Chinese Journal of Rare Metals
基金
甘肃省科技计划项目(20YF8GA058)
温州市工业科技项目(ZG20211003)资助。
作者简介
孙璐(1993-),女,甘肃定西人,博士研究生,研究方向:微动磨损及表面处理,E-mail:sunhsyh12@163.com;通信作者:李元东,教授,电话:0931-2976688,E-mail:liyd@lut.edu.cn。
