CNTs含量对CNTs/Al复合材料力学性能的影响

用羧基化方法对CNTs(碳纳米管)进行预处理,增强其分散性。通过粉末冶金法制备了CNTs含量为0~2.0%的铝基复合材料,并对热挤压前后的力学性能进行了测试。结果表明,复合材料的力学性能均随CNTs含量的增加而增加,CNTs含量为1.0%的铝基复合材料的抗拉强度可达158 MPa,比同样条件下不含CNTs的纯铝抗拉强度(113 MPa)高40%。当CNTs含量在1.0%以下时,CNTs/Al复合材料的硬度、屈服强度和抗拉强度均与CNTs含量的平方根成正比,这表明其主要强化机制应是CNTs的弥散强化。     

等离子喷涂CNTs/AT40复合涂层的制备及表征

采用微弧等离子喷涂技术制备了CNTs/AT40复合涂层,并借助SEM、XRD和热分析仪对涂层进行了组织结构表征、孔隙率计算和高温氧化性能分析.结果表明:涂层组织结构致密,喷涂粒子熔化充分,扁平化程度高,碳纳米管管状结构清晰可见,分布均匀;涂层平均孔隙率都低于5％; CNTs含量为3wt％时,孔隙率最低可达到1.86％;在35～700℃的高温氧化过程中,碳纳米管的起始失重温度为471.29℃,7wt％CNTs/AT40复合涂层的高温氧化性能有一定提高,起始失重温度升高到548.95℃,碳纳米管的失重率从100％下降到25％.     

等离子喷涂CoCrAl-B4C涂层的微观结构与性能

采用大气等离子喷涂技术制备了CoCrAl-B4C涂层,测试了涂层的硬度、结合强度、热震性能及不同条件下的摩擦系数。结果表明:涂层的平均显微硬度为980HV0.2,平均结合强度为17.5MPa,经900℃水淬热震循环10次仍然完好;涂层经700℃热处理后,摩擦系数较低且波动小,水蒸气的存在有利于涂层摩擦系数的降低,其主要原因是涂层表面在热处理与摩擦过程中生成了B2O3和H3BO3自润滑相。     

不同厚度8YSZ热障涂层的结构及性能表征

目的探究厚度变化对8YSZ热障涂层结构、力学性能以及抗热震性能的影响。方法通过超音速火焰喷涂技术(HVOF)和大气等离子喷涂技术(APS)分别制备了Ni CoCrAlTaY粘结层和厚度为500μm、1.0mm、1.5mm的8YSZ陶瓷涂层,采用扫描电子显微镜(SEM)、光学显微镜和X射线衍射仪(XRD)对喷涂粉末和涂层的形貌、物相进行了表征,借助显微硬度计和万能材料试验机分别考察了涂层的硬度和结合强度,最后采用水淬法对涂层的抗热震性能进行了测试。结果不同厚度的8YSZ涂层均由非平衡的四方相(t′-YSZ)组成,且断面呈现出明显的层状结构。随着厚度的增加,涂层中逐渐产生了明显的网状纵向裂纹和边缘界面裂纹。涂层的表面和截面显微硬度都不随厚度的增加而发生显著变化,并且所制备的涂层在整个截面上的显微硬度都比较均匀。涂层的结合强度随着涂层厚度的增加而显著降低。热震试验过程中,三种厚度涂层皆以界面开裂的形式失效,且厚度越大的涂层热震寿命越短。结论 8YSZ热障涂层的厚度变化对其微观形貌、结合强度以及抗热震性能皆有显著影响,而对涂层的物相组成以及显微硬度无明显影响。     

CNTs/SiC/Cu复合材料制备及性能

以碳纳米管(CNTs)、碳化硅(SiC)粉体、锌(Zn)粉和CuSO_4·5H_2O为主要原料,用化学镀的方法制备CNTs /Cu复合粉体,再采用非均相沉淀法制备CNTs/SiC/Cu复合粉体.在750 ℃、100 MPa的制度下进行真空热压烧结后制得CNTs/SiC/Cu复合材料,其中Cu的含量(体积分数,下同)为70%,CNTs的含量(体积分数, 下同)分别为0,3%,5%,8%,12%.利用XRD、SEM分析样品的物相组成和显微结构;利用阿基米德排水法、显微硬度计、三点弯曲法测试了复合材料的密度、显微硬度和抗弯强度.结果表明,随着碳纳米管含量的增加,CNTs/SiC/Cu复合材料的密度、显微硬度和抗弯强度等性能发生相应变化,其中,抗弯强度呈现逐渐升高趋势.与未添加碳纳米管的30SiC/70Cu复合材料相比,添加12%CNTs的12CNTs/18SiC/70Cu 样品,抗弯强度提高了21.45 MPa.     

水平连铸结晶器铜合金内套表面强化工艺及性能研究

选用Ni-Cr-Ti线材作为电弧喷涂材料,通过正交试验法,对用来制作水平连铸结晶器内套的CuC02Be铜合金进行表面强化改性工艺试验.利用金相显微镜、扫描电镜、能谱仪等设备研究了电弧喷涂工艺对涂层微观组织及涂层与基体的结合强度、涂层的显微硬度及热震性能的影响.结果表明:在喷涂空气压力不变的情况下,当喷涂电压35V、喷涂电流140A、喷涂距离150mm时,涂层结合强度达到34.1 MPa,热震41次后涂层没有出现裂纹或剥落,微观组织呈层状结构特征,涂层的显微硬度390.65 HV,且具有较好结合强度和耐热性能.     

纳米ZrO2激光重熔涂层组织与性能分析

采用金相试验、扫描电镜试验、热震试验和显微硬度试验对不同激光重熔工艺下的Y2O3部分稳定ZrO2纳米陶瓷涂层组织与性能进行研究.重点分析了涂层重熔宽度与深度、表面形貌、显微硬度和热震性能随激光比能量的变化规律.结果表明,ZrO2纳米陶瓷涂层的重熔深度和宽度随着激光比能量的增大而增加;涂层的表面成形与激光比能量密切相关;涂层的显微硬度随激光比能量的增大而升高;激光比能量对涂层热震性能的影响十分明显,当激光比能量为37.2 J/mm2时重熔涂层的热震性能最好.     

Al对反应火焰喷涂Al2O3基复相涂层性能的影响

以Al-CuO为主反应体系,利用反应火焰喷涂技术制备了Al2O3基复相涂层.测试了不同Al含量团聚粉喷涂所得涂层与基体的结合强度、显微硬度、孔隙率及耐磨损性能,分析了Al含量对反应火焰喷涂Al2O3基复相涂层性能的影响规律.研究发现,当团聚粉中Al过量6%(质量分数)时,涂层与基体结合强度为24.6 MPa,显微硬度5149 MPa孔隙率为10.5%,磨损量14.9 mg/h,均较Al不过量时明显提高,具有良好的综合性能.     

TiC-Mo2FeB2系复合涂层的组织与性能

用真空液相烧结法在钢基体表面制备了TiC-Mo2FeB2系复合涂层,测定了TiC-Mo2FeB2系复合涂层-钢基体界面结合强度及界面结合区的显微硬度变化,研究了复合涂层的显微组织与界面微观结构和界面区元素分布。结果表明,涂层与钢基体之间具有较高的结合强度,当TiC含量为8%时结合强度最高为820.66 MPa,显微维氏硬度为12.06 GPa,在复合涂层-钢基体结合界面处,存在一个由涂层高硬度到钢基体低硬度的狭窄过渡区,并且两相之间形成了良好的冶金结合。     

微弧等离子喷涂制备莫来石/金属复合热障涂层

运用微弧等离子喷涂制备了莫来石/金属复合热障涂层.研究了涂层的微观结构、结合强度、隔热性能和抗热震性能.复合涂层结构为莫来石颗粒被"包裹"在金属层片状结构中;涂层的结合强度大于30 MPa.随着涂层中莫来石含量的增加,涂层的隔热性能有所提高,随涂层表面温度的升高,涂层的隔热温度也不断提高,涂层的最高隔热温度为125℃.1 150℃的水淬热震试验表明,基体变形是导致涂层失效的重要原因之一,随着涂层中莫来石含量的增加,涂层的抗热震次数先增加后减小,粉末中莫来石含量为40%的涂层的抗热震性能最好,抗热震次数最多为72次.     

Microstructure and properties of WC reinforced Ni-based composite coatings with Y2O3 addition on titanium alloy by laser cladding

ABSTRACT

In this study, WC reinforced Ni-based composite coatings with Y₂O₃ addition were deposited on Ti-6Al-4V titanium substrate by laser cladding. The phases, microstructure, microhardness and wear resistance of the composite coatings were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, microhardness tester and wear tester. The results showed that good metallurgical bonding was achieved between the composite coatings and substrate. The phases mainly were γ-Ni, TiC, TiB₂, Ni₃B, M₂₃C₆ and WC. Most of the WC was dissolved in small pieces of WC during the laser cladding process. The microhardness of the composite coatings was about 3 times that of the titanium substrate and the wear resistance of the composite coatings had a significant increase.     

爆炸喷涂WC-12Co/MoS_2复合涂层的摩擦磨损性能

为进一步提高爆炸喷涂WC-12Co涂层的耐磨性,在WC-12Co合金粉末中添加不同比例的MoS2粉末,利用爆炸喷涂技术在Q235钢表面制备了系列WC-12Co/MoS2复合涂层.采用金相显微镜、扫描电子显微镜、X射线衍射仪、显微硬度计及摩擦磨损试验机对WC-12Co/MoS2复合涂层的微观组织形貌、结构、显微硬度、摩擦磨损性能进行了研究.结果表明,MoS2均匀的分布于复合涂层中,当MoS2含量为2%时,复合涂层的硬度、致密度变化不大,但摩擦系数和磨损率大幅度下降,分别为WC-12Co涂层的50%和36%.随着MoS2含量的增加,复合涂层的摩擦系数和磨损率均呈上升趋势.     

AZ91D镁合金等离子喷涂Ni-Al/陶瓷涂层的组织和性能

以Ni-Al为粘结层,在AZ91D镁合金基体上等离子喷涂Ni-Al/Al2O3、Ni-Al/Al2O3-13%TiO2(Ni-Al/AT13)、Ni-Al/Al2O3-20%TiO2(Ni-Al/AT20)复合涂层及Ni-Al/Al2O3/Al2O3-13%TiO2/Al2O3-20%TiO2(Ni-Al/Al2O3/AT13/AT20)梯度涂层,利用SEM、EDS和XRD分析涂层的微观组织特征,通过硬度、拉伸和热震实验研究涂层硬度、结合强度和抗热震性能,并与直接喷涂Al2O3、AT20的涂层进行比较。结果表明:Ni-Al粘结层因"自粘结"效应与基体形成较为致密并具有冶金结合的界面,且与Al2O3、AT13和AT20陶瓷层互有渗透、交叉和啮合,涂层致密性及结合力大为提高,表现出优良的抗热震性能。Al2O3涂层主要由亚稳态γ-Al2O3组成,AT20涂层以Al2O3和Al2TiO5为主。镁合金表面喷涂Al2O3陶瓷层后硬度大幅提高,由于加入TiO2,AT13和AT20涂层的硬度略低于Al2O3涂层的。Ni-Al/Al2O3-TiO2复合陶瓷的涂层结合强度高于Ni-Al/Al2O3单一陶瓷涂层的,而Ni-Al/Al2O3/AT13/AT20梯度涂层的结合强度比Ni-Al/AT20涂层的更高。     

Characterization and properties of the MgF2/ZrO2 composite coatings on magnesium prepared by micro-arc oxidation

Through micro-arc oxidation, the MgF₂/ZrO₂ composite coatings were prepared on magnesium at the different applied voltages (in the range of 400-550 V) in a zirconate electrolytic solution. The morphologies, phase components, microhardness, bond strengths, and corrosion resistances of the composite coatings were investigated. The effect of the applied voltages on the characteristics and properties of the composite coatings and the basic formation mechanism of the coatings were also discussed. The results indicate that the composite coatings are relatively dense and uniform in thickness, and predominantly composed of MgF₂, tetragonal ZrO₂ (t-ZrO₂) and monoclinic ZrO₂ (m-ZrO₂). The composite coatings exhibit a gradient distribution in phase component from the surface to the inner part. It is found that the applied voltage plays an important role in the characteristics and properties of the composite coatings. With the increase of the applied voltage, the thickness and the t-ZrO₂ content of the composite coatings increase, while the m-ZrO₂ content decreases and no significant variation is observed in the MgF₂ content. Moreover, the surface microhardness and bond strength of the coatings increases with the applied voltage increasing. The microhardness values display a gradient distribution in the cross sections of the coatings, and the maximum microhardness value and its corresponding position in the cross sections are related to the applied voltage. In addition, the corrosion resistances of the composite coatings on magnesium surface are obviously superior to the magnesium substrate in the NaCl solutions, and the effect is more remarkable at higher voltage.     

常压化学气相沉积SiO2涂层的制备及其性能研究

    以正硅酸乙酯(TEOS)为源物质,空气为载气和稀释气,采用常压化学气相沉积法(APCVD)在HP40钢表面制备了SiO₂涂层.采用光学显微镜、扫描电子显微镜、能量色散能谱仪、D＼MAX-C型X射线衍射仪、显微硬度仪等,研究了SiO₂涂层的组织结构、表面形貌、物相组成和显微硬度;并用热震实验法和剥离实验法研究了涂层与HP40基体的结合强度.结果表明,所制备的SiO₂涂层厚度约为1 μm,由细小颗粒组成,颗粒比较均匀、大部分颗粒的粒径均在1 μm以下;涂层无明显孔隙,与基体的结合强度较高;其显微硬度明显高于HP40基体.     

Effect of nano-sized CeF3 on microstructure, mechanical, high temperature friction and corrosion behavior of Ni-W composite coatings

Ni-W-CeF₃ composite coatings were prepared by electrodeposition in a Ni-W plating bath containing CeF₃ nano-particles. The shape and size of the CeF₃ nano-particles and the surface topography of the composite coatings were observed using an environmental scanning electron microscope, and the component and structure analysis was characterized by means of XRD. A microhardness tester was employed to investigate the microhardness of the coatings. The high temperature friction behavior and corrosion resistance of the coatings against molten glass were investigated by using a high temperature tribometer. It was found that the CeF₃ nano-particles appeared in the coatings as microspheres of a diameter less than 50 nm. The addition of CeF₃ nano-particles led to changes in morphologies of the composite coatings by refining the size of crystalline bulks. Therefore, the Ni-W-nanoCeF₃ composite coatings had more compact and fine granular morphologies. The co-deposited CeF₃ nano-particles were uniformly distributed in the Ni-W matrix and had contribution to greatly increasing the microhardness, high temperature tribological and anti-corrosion properties of the Ni-W alloy, furthermore the mechanism of anti-friction and anti-corrosion is discussed.     

Effects of SiC Volume Fraction and Particle Size on the Deposition Behavior and Mechanical Properties of Cold-Sprayed AZ91D/SiCp Composite Coatings

AZ91D/SiC_p composite coatings were fabricated on AZ31 magnesium alloy substrates using cold spraying. The effects of SiC volume fraction and particle size on the deposition behavior, microhardness, and bonding strength of coatings were studied. The mean sizes of SiC particles tested were 4, 14, and 27 μm. The results show that fine SiC particles (d _0.5 = 4 μm) are difficult to be deposited due to the bow shock effect. The volume fraction of SiC particles in composite coatings increases with the increasing SiC particle size. The microhardness and bonding strength of composite coatings also show increases compared with AZ91D coatings. The volume fractions of SiC particles in the original powder were set at 15, 30, 45, and 60 vol.%. The corresponding contents in composite coatings are increased to 19, 27, 37, and 51 vol.%, respectively. The microhardness of composite coatings also increases as the volume fraction of SiC particles increases.     

Effects of Cu content on microstructures and compressive mechanical properties of CNTs/Al-Cu composites

The carbon nanotubes (CNTs) reinforced Al-Cu matrix composites were prepared by hot pressing sintering and hot rolling, and the effects of Cu content on the interfacial reaction between Al and CNTs, the precipitation behavior of Cu-containing precipitates, and the resultant mechanical properties of the composites were systematically investigated. The results showed that the increase of Cu content can not only increase the number and size of Cu-containing precipitate generated during the composite fabrication processes, but also promote the interfacial reaction between CNTs and Al matrix, leading to the intensified conversion of CNTs into Al₄C₃. As a result, the composite containing 1 wt.% Cu possesses the highest strength, elastic modulus and hardness among all composites, due to the maintenance of the original structure of CNTs. Moreover, the increase of Cu content can change the dominant strengthening mechanisms for the enhanced strength of the fabricated composites.     

AZ31B合金热化学反应热喷涂复相陶瓷涂层制备及性能

采用机械球磨和PVA（聚乙烯醇）造粒制成喷涂复合粉末,采用热化学反应火焰喷涂技术,在镁合金AZ31B表面制备Al2O3,基复相陶瓷涂层．利用x射线衍射（XRD）、扫描电镜（SEM）分析了喷涂复合粉末和复合陶瓷涂层的组成及形貌,并对涂层的热震性能、致密性、显微硬度和耐磨性进行测试．结果表明,复合粉末经12h球磨后有化学反...     

Fabrication and characterization of Al2O3-metal composite coating on steel plate with nonpressure combustion synthesis

Al2O3-metal composite coatings with different reactants and diluents were fabricated on mild steel plate with nonpressure combustion synthesis process. The coat-ings were characterized by means of X-ray diffraction, scanning electron microscopy, and energy-dispersive spec-trometry, respectively. Thermal shock tests were carried out to determine the bond strength of the coating with the steel substrate. The results indicate that the coating is composed of α-A1203, α-（Fe-Cr） and Al2SiO5 as the main phases. It is found that the coating with the diluents of Al2O3-SiO2 and transition layer of Al2O3-Cr presents the hi.ghest hardness of 2270 HV0.2 and the lowest porosity of 3.93 %. Owing to a metallurgical bond of the coating-to-substrate, the coating exhibits a good thermal shock resistance.