Self-Lubricating PEO Coating on an Al Alloy Produced by Vacuum Impregnation Post-treatment

The objective of this research was to develop a novel self-lubricating coating on an AA6061 aluminum alloy.Three coatings were prepared by the plasma electrolytic oxidation(PEO) process using 50-, 500-, and 1000-Hz pulsed direct current, respectively. The as-deposited coatings were then post-treated using two different methods, viz., ultrasonic vibration-aided vacuum oil impregnation(UVOI) and oil impregnation under ambient pressure(OIAP). After posttreatment, an oil-containing, self-lubricating top layer was formed on the coatings. The effects of the coatings' surface morphologies and structures on their oil-holding capabilities were discussed. The results revealed that coatings prepared with higher frequency had a greater oil-holding capacity using OIAP post-treatment, while those prepared with lower frequency had a greater oil-containing capability using UVOI post-treatment. These phenomena are related to the morphologies of the coatings produced with various current modes. The tribological properties of the coatings before and after post-treatments were investigated by pin-on-disc sliding wear tests. Due to the formation of a lubricant-containing top layer, the post-treatment coatings had a lower friction coefficient and improved wear resistance compared with the asdeposited coatings. In addition, the coatings after UVOI treatment had better wear performance than those post-treated using the OIAP process. Among all coatings, the coating produced with a 50-Hz pulsed current followed by UVOI posttreatment achieved the lowest friction coefficient(0.03) and best wear resistance when sliding against a Si3N4 ceramic counterface. This study indicates that a novel self-lubricating coating can be prepared by a PEO process combined with vacuum oil impregnation post-treatment.     

阴极电流密度对6061铝合金在含Na2WO4电解液中微弧氧化膜结构和耐磨性能的影响

目的 研究恒流模式下阴极电流密度对6061铝合金在含Na2WO4的电解液中制备的微弧氧化膜厚度、形貌、相组成及耐磨性能的影响。方法 固定阳极电流密度为5.0 A/dm²,阴极电流密度分别为0、1.25、2.5、3.75、5.0 A/dm²,对6061铝合金进行微弧氧化40 min。用涡流测厚仪测量了氧化膜的厚度,用扫描电镜观察了微弧氧化膜的表面形貌和截面形貌,用能谱分析仪分析了氧化膜的表面成分,用X射线衍射分析仪分析了微弧氧化膜的相组成,用往复式摩擦磨损试验机测试了氧化膜的耐磨性能。结果 随着阴极电流密度的增加,氧化膜内的W含量逐渐减少,氧化膜颜色逐渐变浅,氧化膜厚度逐渐增加。微弧氧化膜的主要组成相为α-Al2O3和γ-Al2O3。当阴极电流密度从0 A/dm²增加到3.75 A/dm²时,氧化膜内孔洞的数量和尺寸逐渐减少,孔洞到氧化膜/基体界面的距离逐渐增加,氧化膜的耐磨性能逐渐提升。当阴极电流密度为3.75 A/dm²时,氧化膜的磨损率最低,仅为1.07×10^‒4 mm³/(N.m)。但阴极电流密度增加到5.0 A/dm²时,氧化膜表层出现孔洞和剥落,耐磨性能下降。结论 阴极电流的加入有助于增加6061铝合金微弧氧化膜的厚度,提高氧化膜的致密性和耐磨性能,但过高的阴极电流会导致氧化膜表层出现孔洞,降低耐磨性能。     

Amorphous coatings deposited on aluminum alloy by plasma electrolytic oxidation

Amorphous [Al-Si-O] coatings were deposited on aluminum alloy by plasma electrolytic oxidation (PEO). The process parameters, composition, micrograph, and mechanical property of PEO amorphous coatings were investigated. It is found that the growth rate of PEO coatings reaches 4.44μm/min if the current density is 0.9 mA/mm^2. XRD results show that the PEO coatings are amorphous in the current density range of 0.3 - 0.9 mA/mm^2. EDS results show that the coatings are composed of O, Si and A1 elements. SEM results show that the coatings are porous. Nano indentation results show that the hardness of the coatings is about 3 - 4 times of that of the substrate, while the elastic modulus is about the same with the substrate. Furthermore, a formation mechanism of amorphous PEO coatings was proposed.     

Corrosion and wear resistance of AZ31 Mg alloy treated by duplex process of magnetron sputtering and plasma electrolytic oxidation

In order to improve the wear and corrosion resistance of AZ31 magnesium alloy, a magnetron-sputtered Al layer with a thickness of 11 μm was firstly applied on the alloy, and then treated by plasma electrolytic oxidation (PEO) in an aluminate and silicate electrolytes, respectively. The performance of PEO coatings was investigated by dry sliding wear and electrochemical corrosion tests. The aluminate coating exhibits excellent wear resistance under both 10 and 20 N loads. The silicate coating only shows low wear rate under 10 N, but it was destroyed under 20 N. Corrosion tests show that the Al layer after magnetron sputtering treatment alone cannot afford good protection to the Mg substrate. However, the duplex layer of PEO/Al can significantly improve the corrosion resistance of AZ31 alloy. Electrochemical tests show that the aluminate and silicate coatings have corrosion current densities of ∼1.6×10⁻⁶ and ∼1.1×10⁻⁶ A/cm², respectively, which are two orders lower than that of the un-coated AZ31 alloy. However, immersion tests and electrochemical impedance spectroscopy (EIS) show that the aluminate coating exhibits better long-term corrosion protection than silicate coating.     

纳米Al2O3-40％TlO2复相陶瓷颗粒增强镍基合金复合涂层的摩擦学性能

运用等离子喷涂技术在7005铝合金表面制备Al2O3-40%TiO2纳米结构颗粒增强镍基合金复合涂层,分析其微观结构,研究其在不同载荷和速度条件下的摩擦磨损性能。结果表明：复合涂层主要由γ-Ni、α-Al2O3、γ-Al2O3和金红石型-TiO2等相组成,其摩擦因数和磨损失重较镍基合金涂层显著降低。在轻载3 N 时,复合涂层磨损表面的接触应力较低,主要发生微观切削磨损;当载荷上升至6~12 N时,接触应力高于磨损表面的弹性极限应力,复合涂层的磨损机理变为多次塑变磨损、微观脆性断裂磨损和磨粒磨损。随着速度的增大,磨损表面的接触温度逐渐升高,复合涂层以多次塑变磨损、疲劳磨损和粘着磨损为主。     

Effect of NaOH on plasma electrolytic oxidation of A356 aluminium alloy in moderately concentrated aluminate electrolyte

Plasma electrolytic oxidation(PEO) of cast A356 aluminum alloy was carried out in 32 g/L NaAlO₂ with the addition of different concentrations of NaOH. The stability of the aluminate solution is greatly enhanced by increasing the concentration of NaOH. However, corresponding changes in the PEO behaviour occur due to the increment of NaOH concentration. Thicker precursor coatings are required for the PEO treatment in a more concentrated NaOH electrolyte. The results show that the optimal NaOH concentration is 5 g/L, which improves the stability of storage electrolyte to about 35 days, and leads to dense coatings with high wear performance (wear rate: 4.1×10⁻⁷ mm³·N⁻¹·m⁻¹).     

Wear and corrosion behavior of clay containing coating on AM 50 magnesium alloy produced by aluminate-based plasma electrolytic oxidation

This study aims to examine the effect of clay micro particles addition on the microstructure, wear and corrosion behavior of PEO coatings on AM 50 magnesium alloy. PEO coatings were prepared using an aluminate-based electrolyte with and without the presence of 5 g/L clay particles. The structure and composition of the coatings were evaluated using SEM, EDS and XRD. The wear investigations were conducted using a ball-on-disk tribometer at 2, 5 and 10 N loads. The corrosion behavior of the coatings was examined using polarization and EIS tests in 0.5 wt.%NaCl. The results revealed that the addition of clay particles deteriorated the wear resistance of the coatings under the loads of 5 and 10 N. The SEM examinations of the worn surfaces indicated that a combination of adhesive and abrasive wear mechanisms was activated for the coating with clay particles. The poor wear performance of the clay-incorporated coating was related to its lower adhesion strength and higher roughness. The potentiodynamic polarization examinations revealed that the addition of clay particles slightly decreased the corrosion rate of the coatings. Corrosion resistance of the clay-containing coating was attributed to its compactness, as indicated by the results of EIS tests.     

微弧氧化处理对铝合金耐霉菌腐蚀特性的影响

在2A12铝合金表面制备了微弧氧化膜层,按照国家军用标准霉菌测试方法对微弧氧化膜层的耐腐蚀性能进行了测试,通过扫描电镜(SEM)、X射线衍射分析(XRD)对铝合金基体及微弧氧化膜层霉菌腐蚀前后的微观结构、相组成进行了表征。结果表明,未经过微弧氧化处理的铝合金表面有少量的霉菌生长,表面产生了一定数量的点蚀坑,长霉等级为1级。经过微弧氧化处理试样表面未发现霉菌生长,长霉等级为0级。微弧氧化处理可以有效提高铝合金表面耐霉菌腐蚀性能,扩大其应用范围。     

石墨烯纳米片对D16T铝合金微弧氧化膜层结构与性能的影响

目的研究石墨烯纳米片对D16T铝合金耐磨耐蚀性的影响,为铝合金表面微弧氧化处理技术在油气领域的应用提供理论依据。方法利用微弧氧化技术在含与不含石墨烯的电解液中在D16T铝合金表面制备微弧氧化膜层,采用XRD、SEM、EDS分析了膜层相结构和表面形貌,测试了膜层的粗糙度和显微硬度,通过摩擦磨损和电化学实验研究了石墨烯纳米片对D16T铝合金微弧氧化膜耐磨性和耐蚀性的影响。结果微弧氧化膜层主要由α-Al2O3和γ-Al2O3相组成,石墨烯的添加使Al2O3相的衍射峰值和衍射峰的数量增加,Al衍射峰明显降低;膜层表面平整,表面熔融颗粒较少,表面有大块团聚物堆积。膜层由外部疏松层和内部致密层组成,疏松层微孔数量和微裂纹较少,膜层厚度稍有增加,致密层厚度由不含石墨烯时的0.6μm增至1.6μm。含石墨烯的膜层容抗弧半径明显增加,Bode图中低频阻抗值由5×10^5Ω·cm^2提升至106Ω·cm^2,疏松层电阻由1.57×10^5Ω·cm^2增至1.98×10^5Ω·cm^2,致密层电阻由3.07×10^5Ω·cm^2提升至1.24×106Ω·cm^2;膜层自腐蚀电位由-0.53 V提高至-0.41 V,自腐蚀电流密度由3.15×10^-7 A/cm^2降低至3.97×10^-8 A/cm^2;膜层质量磨损量明显降低,摩擦系数减小,耐磨性增加。结论石墨烯纳米片通过放电通道进入膜层填充膜层中的孔和裂纹,部分石墨烯形成团状覆于膜层表面,使膜层更加平整、致密,膜厚增加,膜层耐磨性和耐蚀性得到明显提升。     

TEM analysis and tribological properties of Plasma Electrolytic Oxidation (PEO) coatings on a magnesium engine AJ62 alloy

In order to reduce the fuel consumption and pollution, automotive companies are developing magnesium-intensive components. However, due to the low wear resistance of the magnesium (Mg) alloys, Mg cylinder bores are vulnerable to the sliding wear attack. In this paper, a Plasma Electrolytic Oxidation (PEO) process was used to produce oxide coatings on a Mg alloy AJ62 (MgAl6Mn0.34Sr2), developed for Mg engine block, to battle against the wear attack. The surface morphology, coating thickness and tribological properties were tailored by adjusting the PEO process parameters. TEM analysis demonstrated that the PEO coatings had a nanocrystalline structure in the inner dense layer next to the substrate. The PEO coatings exhibited a much better wear resistance and a smaller friction coefficient than the uncoated AJ62 substrate. The tribological performance of the PEO-coated Mg alloy was even better than that of a hypereutectic Al-Si alloy currently used for engine applications under a high contact load.     

Investigation of wear and corrosion resistance of nanocomposite coating formed on AZ31B Mg alloy by plasma electrolytic oxidation

Ceramic-WC coatings were prepared on AZ31 B Mg alloy by plasma electrolytic oxidation (PEO) from a phosphate based bath containing suspended tungsten carbide nanoparticles at various process times. Scanning electron microscope results indicated that increase of coating time and incorporation of tungsten carbide into the ceramic coating during the PEO process led to a decrease in the number and diameter of coating pores. Phase analysis showed that the nanocomposite coating was composed of MgO, Mg₃(PO₄)₂ and WC. Tribological properties and corrosion behaviour of uncoated AZ31 B Mg alloy and ceramic coatings were evaluated using a pin-on-disc tribometer and potentiodynamic polarisation technique in 3.5% NaCl solution, respectively. The wear and electrochemical tests showed that wear and corrosion resistance of ceramic-WC nanocomposite coatings were better than ceramic only ones. In addition, wear and corrosion behaviour of coatings improved with increasing the coating time.     

恒电位对TiN涂层在人工海水环境中腐蚀磨损的影响

目的研究不同恒电位对TiN涂层在人工海水环境中腐蚀磨损行为的影响。方法用多弧离子镀系统在316不锈钢上沉积TiN涂层。通过XRD测试、纳米压痕硬度测试、膜基结合力测试、电化学工作站测试、不同恒电位下磨蚀实验和涂层的磨痕截面轮廓测试,分别评价TiN涂层的相结构、硬度、结合力、电化学性能、摩擦系数、磨损率,并通过扫描电子显微镜对涂层表面形貌、截面形貌和磨痕形貌进行分析。结果在摩擦条件下,TiN涂层的开路电位随着滑动摩擦时间的增加而逐渐降低。TiN涂层在不同恒电位(-1V、-0.5 V、OCP、0 V)下滑动摩擦,平均摩擦系数分别为0.392,0.416、0.324、0.348。磨损率分别为1.8117×10-6、3.1123×10-6、4.5958×10-6、7.7724×10-6 mm3/(N·m)。在0.5 V下,涂层被磨穿。TiN涂层在人工海水环境中的主要腐蚀磨损破坏机制为磨粒磨损和疲劳点蚀。结论提高加载电位,涂层的磨损量和磨损率同步增大。在-1、-0.5 V,OCP下,由腐蚀促进磨损的损失量占TiN涂层损失总量的比重逐渐增大,依次为0%、41.78%、61.77%。在0 V时,TiN涂层产生了由磨损促进腐蚀的损失量,占TiN涂层损失总量的比例为6.1%。     

脉冲频率对铝基PEO涂层隔热性能的影响规律及作用机理

在硅酸盐体系下使用等离子体电解氧化(PEO)技术在ZL109铝合金试样表面进行了陶瓷化处理,并采用SEM、XRD、DSC、激光导热仪等方法系统地研究了脉冲频率变化对PEO涂层热性能的影响规律及作用机理。研究表明,脉冲频率主要通过影响涂层的相结构组成及显微结构从而引起隔热性能的变化。当频率为200 Hz时,PEO涂层的热导率最低,为0.113 W/(m·K)。     

Ti2AlNb合金微弧氧化电解液优化及耐磨性研究

目的优化Ti_2AlNb合金微弧氧化的电解液配方,提高Ti_2AlNb合金微弧氧化膜的耐磨性。方法借助SEM、EDS、XRD研究硅酸盐-磷酸盐电解液体系中Na_2MoO_4浓度对Ti_2AlNb合金微弧氧化膜形貌、成分及相结构的影响。利用CFT-I型磨损试验机测试不同微弧氧化膜的摩擦磨损性能。结果电解液中添加Na_2MoO_4后,微弧氧化膜的生长速率增加,膜层中出现了Mo元素且含量也逐渐增加。Na_2MoO_4的加入降低了Ti_2AlNb合金微弧氧化膜的摩擦系数及比磨损率,但微弧氧化膜的耐磨性并非随Na_2MoO_4含量线性提高。含6 g/L Na_2MoO_4的体系中,微弧氧化膜摩擦系数低至0.25左右,比磨损率仅为1.20×10~(-3) mm~3/(N·m),表面呈轻微磨粒磨损特征。结论电解液中的Na_2MoO_4参与了成膜过程,对Ti_2AlNb合金微弧氧化膜的生长有显著的促进作用,有效地改善了Ti_2AlNb合金微弧氧化膜的耐磨性。     

Corrosion and wear properties of electroless Ni-P plating layer on AZ91D magnesium alloy

A direct electroless Ni-P plating treatment was applied to AZ91D magnesium alloy for improving its corrosion resistance and wear resistance. Corrosion resistance of the Ni-P coatings was evaluated by potentiodynamic polarization and immersing experiments in 3.5% NaCl solution. The wear resistance of the coatings was investigated by the wear track and the mass change after ball-on-disk experiment. The results show that corrosion resistance and wear resistance of the AZ91D alloy are greatly improved after direct electroless Ni-P plating. No discoloration is noticed until 4 d of immersion in 3.5% NaC1 solution. Potentiodynamic polarization experiments show that the free corrosion potential of magnesium alloy is shifted from -1 500 mV to -250 mV and passivation occurs at 1 350 mV after direct electroless plating. The friction coefficients and wear rates of Ni-P coating and Ni-P coating after tempering are 0.10-0.351, 9.038×10^-3 mm^3/m and 0.13-0.177, 3.056×10^-4 mm^3/m, respectively, at a load of 1.5 N with dry sliding. Although minor hurt on corrosion resistance was caused, significant improvement of wear resistance was obtained after tempering treatment of the coating.     

添加CeO2对铝合金表面激光熔覆铝钛熔覆层性能的影响

利用激光熔覆技术,研究稀土氧化物CeO₂的添加对铝钛复合熔覆层性能的影响。首先分析了搭接率对熔覆层微观组织、显微硬度及摩擦磨损性能的影响,然后在40%搭接率的条件下,研究了CeO₂的添加量对熔覆层性能的影响。结果显示,当搭接率为40%时熔覆层的各项性能最佳,显微硬度为284.82 HV0.3,相比基体提高了106%;摩擦因数为0.440,相比基体降低了32%;磨损率也降到了0.0105 mm³·N^-1·m^-1;CeO₂的添加使晶粒得到了细化,熔覆层的显微硬度和耐磨性都得了很大程度的提升,当CeO₂的添加量为8%时,熔覆层整体性能最佳,显微硬度为305.58 HV0.3,相比未添加CeO₂的情况下又提高了7.3%;摩擦因数与未添加前相差不大,但磨损率仅有0.0087 mm³·N^-1·m^-1,相比未添加CeO₂的情况下又降低了17%。     

Influence of Concentrations of KOH and Na_2SiO_3 Electrolytes on the Electrochemical Behavior of Ceramic Coatings on 6061 Al Alloy Processed by Plasma Electrolytic Oxidation

In this study,ceramic coatings were deposited on 6061 Al alloy using a plasma electrolytic oxidation(PEO)technique,and the effect of concentrations of KOH and Na_2SiO_3 as electrolytes for PEO process was studied on microstructure,chemical composition,and electrochemical behavior of PEO coatings formed on the 6061 Al alloy.The results indicated that the increase in concentration of KOH led to rise in electrical conductivity of electrolyte.Consequently,the breakdown voltage reduced,which in turn improved the surface quality and the corrosion behavior.Moreover,the increase in concentration of Na_2SiO_3 resulted in the increase in incorporation of Si in the coating,which led to a higher corrosion potential in the concentration of 4 g L~(-1).According to this investigation,the best protection behavior of coatings can be obtained when the KOH and Na_2SiO_3 concentrations in PEO electrolyte are equal to 4 g L~(-1).     

电解液对 2A12 铝合金硬质阳极氧化膜层性能的影响

目的对硫酸、混合酸电解液体系中制备的2A12铝合金硬质阳极氧化膜层性能进行研究,找出混合酸电解液体系对2A12铝合金硬质阳极氧化过程的影响机理,为改善膜层的耐蚀性能提供一种思路。方法通过对膜层厚度、显微硬度、微观形貌、极化曲线、交流阻抗试验结果进行分析,研究不同电解液对2A12硬质阳极氧化膜层性能的影响。结果在有机酸的活性吸附作用下,混和酸电解液解决了硫酸电解液制备2A12铝合金硬质阳极氧化膜存在的厚度、硬度不均匀及烧蚀现象,制备的膜层厚度范围为35~38μm,硬度范围为386~407HV0.05,具有厚度和硬度分布均匀、离散性小的特点。极化曲线及电化学交流阻抗分析表明,混合酸电解液体系中制备的2A12铝合金硬质阳极氧化膜层未进行封孔处理时,膜层的自腐蚀电位为-619.93 m V,阻挡层电阻为1.4×105Ω·cm2;封孔处理后,膜层的自腐蚀电位为-74.69m V,阻挡层电阻为2.376×106Ω·cm2。这说明封孔处理能够改善阻挡层的质量,显著提高膜层的耐腐蚀性能。结论采用混合酸电解液体系能够稳定制备出2A12铝合金硬质阳极氧化膜层,制备的膜层应进行封孔处理。     

镁合金表面沉积铜钨复合涂层工艺及涂层性能研究

目的提高镁合金表面的耐蚀耐磨性。方法采用冷喷涂与化学气相沉积(CVD)相结合的方法在镁合金表面制备出Cu/W复合涂层,并对复合涂层的结构、成分、组织形貌、耐磨性、耐蚀性、结合力进行分析。结果镁合金基体沉积Cu/W复合涂层后,表面硬度提高了687.1HV,磨损率从0.032%降到0.020%,腐蚀电位正移了1.3 V,临界载荷相比直接化学气相沉积W涂层提高了120.5 N。结论Cu/W复合涂层显著提高了镁基体的耐磨、耐蚀性,涂层与基体结合力较高。     

TiC颗粒增强镍基合金复合涂层的摩擦学性能(英文)

运用等离子喷涂技术制备了TiC颗粒增强镍基合金复合涂层,分析了TiC颗粒增强镍基合金复合涂层的微观结构,研究了其摩擦磨损行为与机理。结果表明:TiC颗粒增强镍基合金复合涂层主要由γ-Ni,CrB,Cr7C3和TiC构成;复合涂层与基底材料间形成了厚度为9.4μm的过渡层,达到了冶金结合。当TiC颗粒含量为30%(体积分数)时,复合涂层的摩擦系数和磨损率均最低,即其摩擦系数为0.33,较纯镍基合金涂层降低了30%;其磨损率为0.3×10-3mm3/m,是纯镍基合金涂层的1/3。当载荷在6～10N的范围内时,复合涂层呈轻微磨损,其磨损机理主要为粘着磨损;当载荷达到12N时,复合涂层产生严重磨损,其磨损机制转变为硬质相的脱落和转移层的层脱剥落。