纳米TiO_2含量对等离子喷涂Al_2O_3/TiO_2涂层耐磨性的影响

采用大气等离子喷涂设备在H13热作模具钢表面制备了不同纳米TiO_2含量的Al_2O_3/TiO_2陶瓷复合涂层,并应用扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度计、摩擦磨损试验机等研究了陶瓷复合涂层的微观形貌、物相组成、显微硬度及摩擦磨损性能。结果表明,不同纳米TiO_2含量的Al_2O_3/TiO_2陶瓷涂层均为层片结构,存在一定的孔隙和裂纹,纳米TiO_2添加可以改善涂层表面质量。XRD图谱显示陶瓷涂层主要由α-Al_2O_3、γ-Al_2O_3和Rutile-TiO_2相组成,Al_2O_3再结晶过程中部分α-Al_2O_3转变为γ-Al_2O_3,且再结晶过程发生晶粒细化。涂层显微硬度平均值为1153 HV0.2。纳米TiO_2添加可以降低涂层摩擦因数,但其含量对涂层耐磨性影响不明显。     

等离子喷涂纳米Al2O3-13TiO2陶瓷涂层研究

以常规和纳米团聚体Al2O3-13TiO2(ω/%,下同)复合陶瓷粉末为原料,采用等离子喷涂工艺在TiAl合金表面制备常规和纳米结构陶瓷涂层.用扫描电镜(SEM)和X射线衍射(XRD)仪分析粉末和涂层形貌、微观结构及相组成,同时对纳米结构涂层的微观组织形成机制进行了讨论.结果表明:常规复合陶瓷涂层呈典型的等离子喷涂层状堆积特征;纳米结构复合陶瓷涂层由部分熔化区以及与常规等离子喷涂类似的片层状完全熔化区组成.根据组织结构的不同,部分熔化区又分为亚微米A12O3粒子镶嵌在TiO2基质相的三维网状或骨骼状结构的液相烧结区和经过一定长大但仍保持在纳米尺度的残留纳米粒子的固相烧结区,不同的部分熔化组织源于复合陶瓷粉末中A12O3与TiO2之间的熔点差异.由于等离子喷涂过程中涂层沉积时的快速凝固作用,不管是常规还是纳米涂层都以亚稳相γ-A12O3为主.     

TC4钛合金表面Al_2O_3-TiO_2涂层的制备及其性能

利用等离子喷涂在TC4钛合金基体上制备了Al_2O_3-Ti O_2涂层。并进行了涂层表面形貌分析、XRD分析、涂层显微硬度测试及热震性试验等。结果表明:等离子喷涂制备的Al_2O_3/Ti O_2涂层呈层状分布,存在有全熔相区和未熔粉末颗粒及一定数量的孔隙;随喷涂电压的增加,涂层中未熔粉末颗粒减少,涂层表面平均硬度升高。在喷涂电压72 V,电流500 A时制备的Al_2O_3/Ti O_2涂层平均硬度达978.2 HV 0.3,耐磨性较基体显著提高。涂层与过渡层、过渡层与基体的机械结合是其热震性能较低的主要原因之一。     

等离子喷涂纳米复合陶瓷涂层的组织结构及其形成机理

以Al2O3-13%TiO2(质量分数)团聚体复合陶瓷粉末为材料,采用等离子喷涂工艺在TiAl合金表面制备纳米结构陶瓷涂层.用扫描电镜(SEM)和X射线衍射仪(XRD)分析粉末和涂层形貌、微观结构及相组成,讨论涂层的微观组织形成机理.结果表明:纳米结构复合陶瓷涂层由部分熔化区以及与常规等离子喷涂类似的片层状完全熔化区组成;根据组织结构的不同,部分熔化区又分为液相烧结区(亚微米Al2O3粒子镶嵌在TiO2基质相的三维网状或骨骼状结构)和固相烧结区(经过一定程度长大但仍保持在纳米尺度的残留纳米粒子);等离子喷涂使部分α-Al2O3以及全部θ-Al2O3转变为亚稳态γ-Al2O3;纳米结构复合陶瓷涂层中的完全熔化区、液相烧结区及固相烧结区分别由等离子喷涂过程中纳米团聚体粉末中温度高于Al2O3熔点、介于TiO2熔点到Al2O3熔点之间以及低于TiO2熔点区域沉积获得,纳米结构涂层中不同部分熔化组织源于复合陶瓷粉末中Al2O3与TiO2之间的熔点差异.     

等离子喷涂氧化铝复合涂层的研究进展

等离子喷涂Al_2O_3复合涂层由于优异的耐磨、耐热、耐腐蚀等特性得到了广泛应用。从Al_2O_3复合涂层等离子喷涂制备方法、Al_2O_3复合粉末材料、Al_2O_3梯度涂层、等离子喷涂Al_2O_3复合涂层的工艺等几个方面探讨了等离子喷涂Al_2O_3复合涂层的研究现状,并对该涂层的研究进行了展望。     

纳米Al_2O_3对等离子喷涂ZrC-ZrSi_2复合涂层结构与性能的影响

大气等离子喷涂ZrC-ZrSi_2陶瓷涂层的孔隙率高,提高等离子喷涂ZrC-ZrSi_2陶瓷涂层的致密度成为亟待解决的问题。在TC4钛合金表面采用大气等离子喷涂ZrC-ZrSi_2复合粉和ZrC-ZrSi_2-Al_2O_3复合粉分别制备两种复合涂层。研究纳米Al_2O_3对等离子喷涂ZrC-ZrSi_2复合涂层组织结构与性能的影响。结果表明,添加了Al_2O_3的ZrC-ZrSi_2复合涂层的组织结构更为致密,相较于ZrC-ZrSi_2复合涂层具有更优异的力学性能。熔点相对较低的Al_2O_3能够在喷涂焰流中先熔化,熔融态的Al_2O_3能够填充在ZrC-ZrSi_2复合涂层的孔洞处,提高复合涂层的致密度,改善涂层的力学性能。研究成果可为提高大气等离子喷涂制备含高熔点组分复合涂层的致密度提供指导。     

Al2O3对等离子喷涂Cr2O3/TiO2/Al2O3/SiO2复合陶瓷涂层性能影响研究

目的研究Al_2O_3添加量对Cr_2O_3/TiO_2/Al_2O_3/SiO_2四元复合陶瓷涂层性能的影响。方法采用等离子喷涂技术在油气管道X80管线钢基体表面制备出具有不同Al_2O_3含量的四元复合陶瓷涂层。另外,为探究基体温度对涂层性能的影响,所有涂层均在等离子喷枪预热及室温的两种基体上制备。所制涂层的气孔率、硬度、结合力及电化学腐蚀性能分别采用煮沸称重法、维氏硬度计、划痕仪、电化学工作站进行检测,并用X射线衍射仪(XRD)、扫描电镜(SEM)分析不同Al_2O_3含量涂层的物相组成和形貌特征,研究Al_2O_3含量对涂层各性能的影响。结果随着Al_2O_3含量的增加,Cr_2O_3/TiO_2/Al_2O_3/SiO_2四元复合陶瓷涂层的气孔率呈现先降低后增加的趋势,相对应的四元复合陶瓷涂层的结合力、维氏硬度则先增加后降低。当Al_2O_3质量分数为60%时,四元复合陶瓷涂层的性能最优,气孔率为3.6%,硬度为824.6HV,结合力为53.8N。电化学腐蚀测试表明,Al_2O_3能增强涂层的耐腐蚀性能,Al_2O_3质量分数为60%时,涂层自腐蚀电位最高,为-0.28 V。另外,在基体预热和不预热条件下,所制涂层性能随Al_2O_3含量的变化一致,但是基体预热比不预热更有利于涂层性能的提高。结论 Al_2O_3的添加不仅能够有效降低涂层Cr含量,还能显著提升四元复合陶瓷涂层的各项性能,特别是耐腐蚀性。此外,等离子喷涂前对基体进行预热,有利于涂层性能提高。     

特征喷涂参数对等离子喷涂纳米 Al2 O3 -13%TiO2涂层微观结构及耐磨性能的影响

目的研究等离子喷涂纳米Al2O3-13%TiO2的特征喷涂参数(CPSP)对涂层微观结构及耐磨性能的影响,探索更合理的等离子喷涂工艺参数。方法采用等离子喷涂,在Q235钢表面制备过渡层为NiCrAl、陶瓷层为纳米Al2O3-13%TiO2的涂层系统。对涂层试样进行高温和常温磨损性能测试,并对比分析喷涂粉末、涂层的微观结构和相组成。结果纳米涂层为微观双模结构,由部分熔化区和完全熔化区组成,存在裂纹、孔隙等缺陷,其主要物相为α-Al2O3,γ-Al2O3和rutile-TiO2。纳米涂层磨损失效的主要原因是内部板条的分层剥落和涂层表面材料的塑性变形切削。结论随着CPSP的增大,纳米涂层的耐磨性能增强,且高温磨损性能较室温磨损性能为差。纳米Al2O3-13%TiO2涂层微观结构中部分熔化区结构和纳米晶粒的存在显著提高了涂层的耐磨性。     

TiAl合金表面激光重熔纳米陶瓷涂层

采用等离子喷涂和激光重熔复合工艺在TiA l合金表面制备了纳米A l2O3-13wt%TiO2复合陶瓷涂层。为了使重熔后的陶瓷涂层保留一定的纳米结构组织,采用相对较低的激光功率和能量密度进行重熔。用扫描电镜(SEM)和X射线衍射仪(XRD)分析了涂层形貌、微观结构和相组成。结果表明,等离子喷涂纳米陶瓷涂层由纳米颗粒完全熔化区和部分熔化区两部分组成,具有等离子喷涂态的典型层状结构;由于受到激光功率、能量密度、陶瓷材料热物性参数和涂层厚度等因素的综合影响,重熔后陶瓷涂层出现了明显的分层结构特征;依据组织形态的不同,可将其大致分为:重熔区、烧结区和残余等离子喷涂区。重熔区由致密细小的等轴晶组成,并且保留了部分来源于原等离子喷涂部分熔化区的残留纳米粒子。由于等离子喷涂过程中涂层沉积时的快速凝固作用,涂层以亚稳相-γA l2O3为主,经过激光重熔处理后,-γA l2O3又重新转变为稳定相-αA l2O3。     

Al_2O_3/MoS_2复合涂层的制备及摩擦磨损性能

以大气等离子喷涂工艺制备的Al_2O_3陶瓷涂层为模板,利用陶瓷涂层中存在的孔隙和微裂纹,采用水热反应在其内部原位合成具有润滑特性的MoS_2,制备出Al_2O_3/MoS_2的复合涂层。结果表明,通过水热反应在陶瓷涂层原有的微观缺陷中成功合成了MoS_2,合成的MoS_2固体粉末呈类球形状,并且这球状的粉末是由纳米片层状的MoS_2搭建组成的。摩擦试验结果表明,与纯Al_2O_3涂层相比,复合涂层中由于MoS_2润滑膜的形成,其摩擦因数和磨损率都显著降低,且载荷越大,复合涂层的摩擦性能越好。     

等离子喷涂TiO_2涂层及其光催化性能研究

采用等离子喷涂方法在304不锈钢表面制备了TiO2、AT40（40％TiO2,60％Al2O3）涂层,研究了涂层对甲基橙的光催化降解性能。采用金相分析方法和扫描电镜（SEM）观察了涂层微观结构,用x射线衍射法分析了涂层的相结构。结果表明：涂层与基体结合紧密,表面的孔隙有利于降解率的提高,锐钛型TiO2的含量是影响光催化效果的关键,纯TiO2涂层的降解率高于AT40涂层。     

等离子喷涂Al2O3-13%TiO2复合陶瓷涂层的组织及热氧化性能的研究

采用大气等离子喷涂法在Q235钢上喷涂了常规微米、纳米Al2O3-13%TiO2复合涂层,对2种涂层进行了高温热氧化实验。利用XRD对比分析了2种涂层及其相应粉末的相组成,利用SEM观察了涂层的表面、截面形貌,并运用EDS对2种涂层的组分分布情况进行分析,比较2种涂层的不同结构及热氧化性能,初步探讨了涂层热氧化失效的原因。结果表明:2种粉末在喷涂之后,涂层中的α-Al2O3均有所减少,生成了γ-Al2O3,金红石TiO2相转变成了板钛矿型TiO2相,增加了涂层的内应力,加剧了裂纹的扩展;常规微米涂层中的孔洞细小但密集,纳米涂层中的孔洞较大但不密集,且大部分的气孔都存在于部分熔化区的内部;涂层在喷涂过程中所生成的气孔以及热氧化过程中由于热应力而产生的裂纹是造成涂层失效的直接原因。     

等离子喷涂超高温热障涂层用纳米结构La2(Zr0.75Ce0.25)2O7球形喂料的研究

目的通过纳米粉体造粒技术制备出适合热喷涂超高温用纳米结构La2(Zr(0.75)Ce(0.25))2O7球形喂料,进而采用热喷涂方法制备出纳米结构的热障涂层,以满足下一代热障涂层服役温度需求。方法以化学共沉淀法合成的纳米La2(Zr(0.75)Ce(0.25))2O7粉末为原料,通过球磨、喷雾干燥及热处理工艺制备出纳米结构的La2(Zr(0.75)Ce(0.25))2O7喂料,进而采用大气等离子喷涂方法制备出纳米结构La2(Zr(0.75)Ce(0.25))2O7热障涂层。利用扫描电镜(SEM)和透射电镜(TEM)对原始纳米粉体、纳米喂料及喷涂态涂层进行显微形貌和组织结构分析。此外,通过电感耦合等离子体原子发射光谱法(ICP-AES)对制备的纳米喂料进行成分分析。结果制备出的纳米结构La2(Zr(0.75)Ce(0.25))2O7喂料表面光滑、呈球形,成分与化学计量比基本一致。相对于原始纳米粉末,喂料晶粒长大并不显著。喷涂态涂层部分晶粒长大,但仍保留纳米结构。结论成功制备出纳米结构La2(Zr(0.75)Ce(0.25))2O7球形喂料及纳米结构热障涂层,有望作为下一代超高温热障涂层材料。     

Effects of critical plasma spray parameter and spray distance on wear resistance of Al2O3-8 wt.%TiO2 coatings plasma-sprayed with nanopowders

Effects of plasma spraying conditions on wear resistance of nanostructured Al₂O₃-8 wt.%TiO₂ coatings plasma-sprayed with nanopowders were investigated in this study. Five kinds of nanostructured coatings were plasma-sprayed on a low-carbon steel substrate by varying critical plasma spray parameter (CPSP) and spray distance. The coatings consisted of fully melted region of γ-Al₂O₃ and partially melted region, and the fraction of the partially melted regions and pores decreased with increasing CPSP or decreasing spray distance. The hardness and wear test results revealed that the hardness of the coatings increased with increasing CPSP or decreasing spray distance, and that the hardness increase generally led to the increase in wear resistance, although the hardness and wear resistance were not correlated in the coating fabricated with the low CPSP. The main wear mechanism was a delamination one in the coatings, but an abrasive wear mode also appeared in the coating fabricated with the low CPSP. According to these wear mechanisms, the improvement of wear resistance in the coating fabricated with the low CPSP could be explained because the improved resistance to fracture due to the presence of partially melted regions might compensate a deleterious effect of the hardness decrease.     

Microstructure and properties of Al2O3-13%TiO2 coatings sprayed using nanostructured powders

The microstructure and wear performance of M203-13% TiO2 coatings prepared by plasma spraying of agglom- erated nanoparticle powders were investigated. SEM analysis showed that the as-sprayed Al2O3-TiO2 coatings comprise of two kinds of typical region： fully melted region and unmelted/partially melted nanostructured region, which is different than the conventional coating with lamellar structure. It is shown that the microhardness of the nanostructured coatings was about 15%-30% higher than that of the conventional coating and the wear resistance is significantly improved, especially under a high wear load. The nanostructured coating sprayed at a lower power shows a lower wear resistance than the coatings produced at a higher power, because of the presence of pores and microstructural defects which are detrimental to the fracture toughness of the coatings.     

Nanostructured yttria stabilized zirconia coatings deposited by air plasma spraying

Nanostructured yttria partially stabilized zirconia coatings were deposited by air plasma spraying with reconstituted nanosized powder. The microstructures and phase compositions of the powder and the as-sprayed nanostructured coatings were characterized by transmission electron microscopy（TEM）, scanning electron microscopy（SEM） and X-ray diffxaction（XRD）. The results demonstrate that the microstructure of as-sprayed nanostructured zirconia coating exhibits a unique tri-modal distribution including the initial nanostructure of the powder, equiaxed grains and columnar grains. Air plasma sprayed nanostructured zirconia coatings consist of only the nontransformable tetragonal phase, though the reconstituted nanostructured powder shows the presence of the monoclinic, the tetragonal and the cubic phases. The mean grain size of the coating is about 42 nm.     

PHOTOCATALYTIC PERFORMANCE OF PLASMA SPRAYED TiO2-ZnFe2O4 COATINGS

A novel TiO2-ZnFe2O4 coating is prepared by plasma spraying. The effects of spraying parameters and the composition of powders on the microstructure, surface morphology and photo-absorption of plasma sprayed coatings are studied. The photocatalytic efficiency of the as-sprayed coatings is evaluated through the photo mineralization of methylene blue, It was found that TiO2 coatings can decompose methylene blue under the illumination of ultraviolet rays, and the degrading efficiency is improved with an increase in the content of FeTiO3 in the coatings. However, the presence of large amount of ZnFe2O4 compound will substantially lower the photocatalytic efficiency of the TiO2-ZnFe2O4 coatings for the unfavorable photo-excited electron-hole transfer process.     

Effect of Critical Plasma Spray Parameters on Microstructure and Microwave Absorption Property of Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript>/Cordierite Coatings

Ti₃SiC₂/cordierite coatings with different critical plasma spray parameters (CPSP) were fabricated via atmospheric plasma spraying method. The microstructure and phase constitution of the as-sprayed Ti₃SiC₂/cordierite coatings were characterized. The effects of CPSP conditions on the electromagnetic shielding, and dielectric and microwave absorption properties of coatings in the frequency of 8.2-12.4 GHz were also measured and investigated. The results showed that both real and imaginary part of the complex permittivity decrease with increasing CPSP values, which can be ascribed to the decomposition of some Ti₃SiC₂ into TiC. The calculated reflection loss of the as-sprayed Ti₃SiC₂/cordierite coatings with different CPSP conditions and thicknesses indicates that coatings with CPSP 0.3, 0.35, and 0.425 exhibit excellent microwave absorption property in the thickness of 1.5 mm. In order to broaden the bandwidth of the coatings, a double-layer coating system was designed. The calculated reflection loss results show that when the thickness of matching layer is 0.3 mm and the thickness of absorbing layer is 1.5 mm, the double-layer coating system shows a proper microwave absorption property with a minimum absorption value of ?17.37 dB at 9.67 GHz and a absorption bandwidth (RL less than ?5 dB) of 4.16 GHz in the investigated frequency.     

纳米氧化锆热障涂层组织结构和高温稳定性能分析

采用大气等离子喷涂技术制备了纳米氧化锆热障涂层.利用FESEM和XRD对纳米氧化锆热障涂层的微观组织和物相组成进行研究.微观组织分析结果表明,纳米氧化锆热障涂层展现出独特的微观复合结构,包括未熔纳米颗粒和柱状晶组织.物相分析结果表明,纳米氧化锆热障涂层主要由非平衡四方相组成.纳米氧化锆热障涂层高温稳定性能试验结果表明,涂层晶粒度随着服役温度和服役时间的增加而增加,但仍保持纳米结构;涂层物相组成不随服役环境的变化而变化.