三维网络结构Al2O3陶瓷/高铬铸铁复合材料干摩擦磨损性能

采用往复式滑动摩擦磨损（SRV）试验机研究了高铬铸铁及三维网络结构Al₂O₃陶瓷增强高铬铸铁复合材料的干摩擦磨损性能,测量了高铬铸铁和Al₂O₃陶瓷/高铬铸铁复合材料在不同摩擦频率及载荷下的摩擦系数和磨损率;用扫描电镜观察磨损表面形貌,并分析了三维网络Al₂O₃陶瓷对复合材料磨损机制的影响。结果表明：陶瓷Al₂O₃与高铬铸铁基体之间具有良好的界面结合,复合材料的摩擦系数随摩擦频率和载荷的变化保持稳定,耐磨性远优于高铬铸铁,而且随着摩擦频率和载荷的增加,Al₂O₃陶瓷/高铬铸铁复合材料的抗磨损性能明显提高,这是由于复合材料中Al₂O₃与高铬铸铁相之间三维空间结构和良好的界面结合有利于摩擦载荷的传递;三维Al₂O₃陶瓷骨架在磨损表面形成硬的网络突体并起承载作用,能有效保护金属基体;磨损机制为氧化磨损及磨粒磨损共同作用。     

电解质浓度对TiB2基刀具表面MAO涂层组织和摩擦性能的影响

研究了以高浓度Na₅P₃O₁₀作为电解液对钛合金实施微弧氧化,并对其表面结构和各成分组成情况进行了分析,之后测试了氧化层的表面硬度及其耐磨特性。研究结果表明:提高Na₅P₃O₁₀浓度后,发生了电导率明显增大现象,反应时间显著缩短。加入50 g/L的Na₅P₃O₁₀涂层的表面形成了尺寸差异较大的微孔,这些微孔的尺寸都在1μm以内,表面较平滑。所有微弧氧化涂层内都存在B、Ti、O。各膜层中主要存在B₂TiO₅,同时形成了B₂O₃与金红石TiO₂衍射峰。逐渐提高Na₅P₃O₁₀含量后,加入50 g/L的Na₅P₃O₁₀涂层试样获得了更高硬度,但硬度变化速率发生了降低。加入50 g/L的Na₅P₃O₁₀涂层具备很高极限载荷,迅速达到了稳定的摩擦状态,因此摩擦系数快速减小到稳定的程度。基体的表面受到了较大破坏,产生了许多磨屑颗粒与犁沟;涂层表现为粘着磨损的特征,可以显著降低粘着磨损的程度。     

空间导电滑环绝缘环片等离子喷涂Al2O3绝缘涂层的性能研究

为解决空间导电滑环中非金属绝缘环片存在的结构稳定性差、加工困难等问题，在2A12铝合金基体上利用大气等离子喷涂技术沉积了Al₂O₃陶瓷涂层，以替代非金属绝缘材料，研究了涂层的物相组成、微观形貌、显微硬度、结合强度和绝缘性能。结果表明：由原始纳米颗粒经过团聚-烧结制备的Al₂O₃球形粉末的物相主要为α-Al₂O₃,喷涂后涂层中的Al₂O₃以α相和γ相共存，涂层与基体的结合良好，涂层的孔隙较低。制备的涂层组织结构均匀致密，涂层内无明显的宏观裂纹和大孔洞，虽未采用封孔处理，但涂层在大气环境下直流电压为1 000 V的绝缘电阻测试中仍表现出较高的绝缘性能，可满足空间导电滑环绝缘环片的服役要求。     

低压冷喷涂热处理复合处理制备Ni2Al3金属间化合物涂层及其滑动磨损特性研究

为制备出以Ni₂Al₃为主相的金属间化合物涂层，将Ni粉、Al粉和Al₂O₃粉按质量比20∶6∶5混合均匀，利用低压冷喷涂方法将混合粉体喷涂到45钢基体表面，制备Ni-Al预涂层，再将预涂层在520℃氩气环境下保温12 h,采用X射线衍射(XRD)和扫描电镜(SEM)对涂层组织和物相进行了分析与表征，测试了涂层的结合力和滑动摩擦磨损特性。结果表明：预涂层经热处理转变为Ni₂Al₃金属间化合物涂层后，表现出良好的减摩、耐磨性能。涂层中Ni和Al固相转变为金属间化合物的驱动力是热处理提供的热能和粉体强烈塑性变形后的形变能的共同作用。     

WC、ZrO2 、Cr2O3 和Al2O3 陶瓷颗粒/ 镍合金复合涂层微观组织结构的分形

采用等离子喷涂工艺, 制备了WC、ZrO₂ 、Cr₂O₃ 和Al₂O₃ 陶瓷颗粒/ 镍合金复合涂层。用X 射线衍射研究了陶瓷颗粒复合涂层相的分布; 用里氏硬度计测量陶瓷颗粒/ 镍合金复合涂层的硬度; 用CSS-1110 电子万能试验机研究陶瓷颗粒复合涂层的弯曲断裂性能。对涂层金相组织结构进行二值化处理, 利用Sandbox 法对陶瓷颗粒在金属基体中的分布进行研究, 得到了不同体积分数下陶瓷颗粒复合材料涂层的分维数。结果表明,陶瓷颗粒/ 镍合金复合涂层分维数随陶瓷颗粒含量的增加而增加, 与陶瓷颗粒种类无关; 陶瓷颗粒/ 镍合金复合涂层硬度和分维数随陶瓷颗粒直径减小而增加。随着分维数的增加, 复合涂层弯曲断裂角下降。      

Al2O3基多孔隔热材料表面Al2O3/MoSi2涂层的制备及其性能

采用刷涂法在Al₂O₃基多孔隔热材料表面制备Al₂O₃/MoSi₂涂层,涂层以硅溶胶作为粘结剂,纳米Al₂O₃与Al₂O₃纤维作为耐高温组分,MoSi₂为高发射率组分。通过SEM、XRD对Al₂O₃/MoSi₂涂层微观表面结构、物相组成进行分析。研究纳米Al₂O₃与Al₂O₃纤维的质量比和MoSi₂含量对Al₂O₃/MoSi₂涂层耐温性能的影响,并对Al₂O₃/MoSi₂涂层的抗热震性能、发射率进行表征。结果表明,当纳米Al₂O₃与Al₂O₃纤维的质量比小于1∶1时,热考核后Al₂O₃/MoSi₂涂层表面无裂纹产生;当纳米Al₂O₃与Al₂O₃纤维的质量比在1∶2~1∶4之间时,Al₂O₃/MoSi₂涂层中的纤维网络较完整。MoSi₂的含量为20%时,Al₂O₃/MoSi₂涂层抗热震实验循环25次后表面保持完好,热考核后在2.5~25 μm波段的平均发射率在0.85左右,具有较高的发射率。      

基于PVD-TiN和TiSiN涂层的Al2O3/TiCN陶瓷刀具及其切削性能研究

采用物理气相沉积(Physical vapor deposition, PVD)工艺在Al₂O₃/TiCN陶瓷刀具表面分别沉积了TiN和TiSiN涂层。通过扫描电子显微镜(SEM)观察涂层微观结构, 采用显微硬度计和划痕仪分别表征涂层硬度和测量涂层与基体的结合强度。通过对涂层刀具进行连续干切削灰铸铁实验, 研究TiN和TiSiN涂层对刀具磨损特征的影响并探讨其磨损机理, 同时研究了涂层对工件加工表面质量的影响。结果表明: PVD涂层可显著提高Al₂O₃/TiCN陶瓷的刀具硬度。TiN涂层和TiSiN涂层可分别提高刀具表面硬度25%和65%, 从而增加刀具耐磨性。两种涂层刀具在连续切削灰铸铁实验中主要的失效机理均是挤压变形下的磨粒磨损, 其中TiN涂层刀具还伴随有粘结磨损; 刀具上的PVD-TiN和TiSiN涂层可以有效保护Al₂O₃/TiCN陶瓷刀具基体, 防止崩刃, 进而改善工件表面加工质量。     

Ti811合金表面激光熔覆Ti2Ni+TiC+Al2O3+CrxSy复合涂层的组织和性能

以TC4+Ni45+Al₂O₃+MoS₂+Y₂O₃混合粉末为熔覆材料,采用同轴送粉技术在Ti811合金表面进行激光熔覆制备复合涂层,使用SEM、EDS和XRD等手段分析了涂层的微观组织,测试了涂层的显微硬度和摩擦磨损性能。结果表明,在激光熔覆过程中Ti811合金中的Ni和C分别与Ti发生反应,原位生成金属间化合物Ti₂Ni和硬质增强相TiC;MoS₂分解后S与Cr发生硫化反应生成了软质润滑相Cr_xS_y。网状形态的Ti₂Ni、近球状和枝晶形态的TiC以及点状的Al₂O₃,均匀分布在熔覆层中。硬质相强化和软质相润滑的共同作用,使激光熔覆层具有较高的显微硬度和较优良的耐磨性能。激光功率为900 W的熔覆层其平均显微硬度值达1303.5HV_0.5,其耐磨性能最佳。     

等离子喷涂Al2O3·TiO2涂层的性能及其在航空发动机篦齿封严中的应用

目前有关Al₂O₃·TiO₂涂层的性能及其在实体件上的应用研究报道较少。为此,利用等离子喷涂设备在GH4169试片上制备了NiAl自粘结底层和Al₂O₃·TiO₂陶瓷面层,并进行了显微组织、显微硬度、结合强度及弯曲性能的测试,基于试验结果以某型号航空发动机实体零件开展了喷涂验证。结果表明：Al₂O₃·TiO₂陶瓷涂层综合性能良好,用于篦齿封严类零件中能有效保护篦齿,防止篦齿磨损,并提高零件的使用性能,延长使用寿命。     

Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料摩擦磨损性能

将Al₂O₃-TiC陶瓷材料与具有固体润滑特性的Al₂O₃-TiC-CaF₂陶瓷材料进行叠层, 通过真空热压烧结制备Al₂O₃-TiC/Al₂O₃-TiC-CaF₂复合叠层陶瓷材料。在环盘式摩擦磨损试验机上进行摩擦磨损实验, 研究该材料在不同载荷、 转速条件下的摩擦系数和磨损率, 分别用SEM及EDS观察材料磨损前后的微观形貌和分析其成分组成, 研究其磨损机制。结果表明: 在相同载荷条件下, Al₂O₃-TiC/Al₂O₃-TiC-CaF₂复合叠层陶瓷材料的摩擦系数和磨损率随着转速的升高而下降, 在相同转速条件下, 其摩擦系数和磨损率随着载荷的增加而下降; Al₂O₃-TiC/Al₂O₃-TiC-CaF₂复合叠层陶瓷材料的磨损机制主要是磨粒磨损和黏着磨损。     

TiB2量对42CrMo齿轮钢表面感应熔覆Ni基涂层组织与性能的影响

为了提高42CrMo钢表面Ni基涂层的耐磨性能,利用感应熔覆工艺处理42CrMo钢的表面制得了具有不同TiB₂含量的Ni基涂层,之后对该涂层实施了能谱、扫描电镜表征,同时对涂层硬度与耐磨性能进行了测试,比较了不同TiB₂含量的镍基涂层在组织形态和性能方面存在的差异性。研究结果表明:微观形貌截面区域的组成结构包括扩散转移带、基体层、涂层共三层。当涂层内含有的TiB₂比例到达15%时,熔覆涂层的组织尺寸达到最小状态。从外往内变化时涂层硬度逐渐降低,而且离扩散转移带的距离越小时对应的涂层硬度也越低。涂层磨损量也表现出了和摩擦系数相近的变化规律,都表现为随TiB₂添加量的增加出现单调降低的变化,在TiB₂添加量到达15%时,涂层磨损形貌中存在明显的麻坑和划痕。     

Effect of volume fraction of carbon fibers on wear behavior of Al/Al2O3/C hybrid metal matrix composites

Wear behavior of Al/Al₂O₃/C hybrid metal matrix composites fabricated by squeeze casting method was characterized. The effects of volume fraction of carbon fiber on wear behavior of hybrid composites was investigated. Wear behavior of Al/Al₂O₃/C composites was characterized by the dry spindle wear test under various sliding speeds.

The wear resistance of Al/Al₂O₃/C composites was remarkably improved over Al/Al₂O₃ composites by adding carbon fibers to Al/Al₂O₃/C composites. Specifically, at the intermediate sliding speed the wear resistance of Al/Al₂O₃/C composites containing 8 vol.% carbon fiber was found to be better than that of the rest of the carbon hybrid composites. From fractographic studies, damaged sections in wear surfaces of hybrid composites at intermediate sliding speed were not observed due to the formation of solid lubrication film. The solid lubrication film which was formed as a result of adding carbon fibers improved the wear resistance of carbon hybrid composites because this film reduced the high friction force between MMCs and counter material.     

Fe/Al2O3复合材料的制备和性能

用石墨埋烧方法制备Fe/Al₂O₃复合材料,对其力学性能和微观结构进行了分析。结果表明:Fe/Al₂O₃复合材料的弯曲强度与断裂韧性均随Al₂O₃含量的升高先升高后降低,当Al₂O₃含量（质量分数）为70%时,其弯曲强度与断裂韧性分别达到602.49 MPa和9.33 MPa·m¹/2,其硬度随Al₂O₃含量先降低后升高。在烧结过程中在Fe颗粒周围形成一种成分为FeO与FeAl₂O₄的壳体,在壳体与Fe颗粒之间存在微裂纹缺陷。壳体的形成和壳体与金属颗粒间的微裂纹钝化了外部应力,从而提高了复合材料的韧性。     

Abrasive wear of Al2O3-reinforced aluminium-based MMCs

The effects of volume fraction, Al₂O₃ particle size and effects of porosity in the composites on the abrasive wear resistance of compo-casting Al alloy MMCs have been studied for different abrasive conditions. It was seen that porosity in the composites is proportional to particle content. In addition, process variables like the stirring speed, and the position and diameter of the stirrer affect of the porosity content in a way similar to that observed for particle content. In addition, the abrasive wear rates of composites decreased more rapidly with increase in Al₂O₃ volume fraction in tests performed over 80 grade SiC abrasive paper than in tests conducted over 220 grade SiC abrasive paper. Furthermore, the wear rates decreased with increase in Al₂O₃ size for the composites containing the same amount of Al₂O₃. Hence, it is deduced that aluminium alloy composites reinforced with larger Al₂O₃ particles are more effective against abrasive wear than those reinforced with smaller Al₂O₃ particles. At the same time the results show that the beneficial effects of hard Al₂O₃ particles on wear resistance far surpassed that of the sintered porosity in the compocasting metal-matrix composites (MMCs). Nevertheless, the fabrication of composites containing soft particles such as graphite favors a reduction in the friction coefficient. For this reason graphite and copper were used in the matrix in different amounts to detect their effect on wear resistance. Finally, it was seen that wear rate of the composites decreased considerably with graphite additions.     

Processing, microstructure and properties of C40 Mo(Si,Al)2/Al2O3 composites

The C40 Mo(Si_0.75Al_0.25)₂/Al₂O₃ composites were prepared by spark plasma sintering (SPS) of mechanically alloyed (MA) powders. The Mo(Si_0.75Al_0.25)₂/0–20 vol.% Al₂O₃ materials, showing micron and submicron composite structure, possess a hardness of 13.9–14.6 GPa but a poor toughness of 1.78–1.80 MPa m^1/2. The addition of 30 vol.% Al₂O₃ leads to the formation of the micron C40 Mo(Si_0.75Al_0.25)₂/Al₂O₃ composite with an intergranular distribution of Al₂O₃, that results in a drop of the hardness to 10.2 GPa and an improvement of the toughness to 3.67 MPa m^1/2. The transition of the cleavage facets to the intergranular fracture with the addition of Al₂O₃ is assumed as the main toughening mechanism.     

片状纳米Al2O3/环氧树脂复合材料的制备及性能

采用水热法制备片状纳米Al₂O₃,经过偶联剂改性后与环氧树脂复合,通过溶液混合法制备了不同填充量的片状纳米Al₂O₃/环氧树脂复合材料,研究了片状纳米Al₂O₃用量对片状纳米Al₂O₃/环氧树脂复合材料介电性能和热性能的影响,利用SEM对复合材料的断口形貌进行了表征。结果表明: 片状纳米Al₂O₃在环氧树脂基体中分散良好;随着片状纳米Al₂O₃填充量的增加,复合材料的起始热分解温度升高、介电强度增大,当片状纳米Al₂O₃的填充量为7wt%时,复合材料的介电强度为 29.58 kV/mm,比纯环氧树脂的介电强度提高了30%;复合材料的介电常数(3.8~4.5)和介电损耗(0.015)比纯环氧树脂稍有增大,但仍维持在较好的介电性能范围内。     

Al_2O_3颗粒镀铜对铜基粉末冶金摩擦材料Al_2O_3-Fe-Sn-C/Cu摩擦磨损性能的影响

通过对陶瓷摩擦组元的表面进行化学镀铜来改善铜基粉末冶金摩擦材料中陶瓷相与基体间的结合效果,从而提高材料摩擦磨损性能。分别采用镀铜Al2O3颗粒和未镀铜Al2O3颗粒与铜粉和铁粉等经混合、压制、加压烧结制备Al2O3-Fe-Sn-C/Cu摩擦磨损试样。测试并分析了摩擦材料的微观结构、力学性能及摩擦磨损性能。结果表明:摩擦组元镀铜可使硬质颗粒与铜基体结合紧密;摩擦材料的布氏硬度增加了12%,弹性模量提高了约7%,摩擦系数提高了5%~10%,线磨损量降低了20%~50%;表面镀铜后的Al2O3颗粒不易脱落,摩擦系数稳定性提高了13%~23%。研究结果表明,摩擦组元表面镀铜可提高材料的综合性能。     

High performance nanocomposites for tribological applications: Preparation and characterization

High performance nanocomposites were prepared by incorporating 0–12 vol.% nano-sized (39 nm) Al₂O₃ particles into PEEK matrix using compression molding. The microhardness and dynamic mechanical properties of the nanocomposites increase with increasing Al₂O₃ content. The wear resistance of the nanocomposites evaluated at a sliding speed of 1.0 m/s and nominal pressure from 0.5 MPa to 1.25 MPa under dry sliding conditions was improved more than threefold at 0.8 vol.% Al₂O₃ content. However, the wear resistance of the nanocomposites containing above 1.67 vol.% Al₂O₃ was deteriorated, despite their higher hardness and stiffness as compared to that of nanocomposites containing lower Al₂O₃ content. The surface roughness of the wear track formed over the countersurface increases with increasing Al₂O₃ content. The coefficient of friction of nanocomposites was higher than that of pure PEEK. SEM and optical microscopy have shown that wear of pure PEEK occurs by the mechanism of adhesion mainly, whereas of nanocomposites by microploughing and abrasion. Energy dispersive spectrometry (EDS) shows that Fe and alloying elements of countersurface transfer to the wear debris at higher Al₂O₃ content.