冷喷涂SiC/Al纳米复合涂层的组织结构与性能

为制备基体相晶粒细小、增强相均匀分布的SiC/Al纳米复合涂层,以Al、SiC为原料,采用高能球磨法获得SiC颗粒弥散分布的纳米晶Al基复合材料粉末,利用冷喷涂技术低温成型制备了SiC/Al纳米复合涂层,分析了SiC含量对复合涂层相结构、晶粒尺寸、微观结构、硬度及磨损性能的影响规律。结果表明：冷喷涂可实现球磨纳米晶复合粉末结构的原位移植,所制备SiC/Al纳米复合涂层组织致密,微米及亚微米级SiC弥散分布在纳米晶Al（约80 nm）基体之上;SiC颗粒对Al基体有明显强化作用,冷喷涂SiC/Al纳米复合涂层的硬度随SiC体积分数的增加而显著增加,50% SiC/Al纳米复合涂层的硬度高达515 HV_0.3,约为Al块材的13倍;冷喷涂SiC/Al纳米复合涂层的耐磨损性能随着SiC含量增加而显著提高,涂层磨损失效机制为磨粒对基体的切削犁沟变形。     

等离子喷涂氧化锆涂层及激光重熔涂层的摩擦磨损性能

采用等离子喷涂制备了常规氧化锆涂层和纳米氧化锆涂层,并对制备的纳米氧化锆涂层进行了激光重熔处理,系统地研究了3种氧化锆涂层(常规、纳米和激光重熔涂层)在常温和高温下的摩擦磨损性能.结果表明,纳米氧化锆涂层耐磨性能明显优于常规氧化锆涂层,而激光重熔处理后的纳米氧化锆涂层在常温和高温下,都表现出最低的摩擦系数和最好的耐磨性能.这3种涂层的表面粗糙程度、涂层孔隙率和裂纹状况明显不同,从而表现出不同的摩擦磨损特性;说明纳米粉末等离子喷涂结合激光重熔技术是提高氧化锆涂层性能的有效方法.     

HVOF喷涂纳米结构WC-12Co涂层的组织结构分析

纳米结构WC-12Co涂层的研究目前已受到了广泛重视,对其组织结构及影响因素的研究有利于提高涂层性能.采用HVOF工艺制备了纳米结构、多峰结构及普通微米结构3种WC-12Co金属陶瓷复合涂层,并采用SEM、XRD等对粉末及涂层的显微形貌、组织结构进行了分析;探讨了粉末在喷涂过程中的氧化脱碳机理,并指出了与之相关的影响因素.结果表明:纳米结构WC-12Co涂层结构致密,孔隙率低,与基体结合状态良好;纳米粉末在喷涂过程中比微米粉末氧化失碳严重,并发生了不同的纳米晶粒的长大;纳米粉末在喷涂过程中的氧化脱碳程度不仅与喷涂工艺有关,还在很大程度上取决于粉末本身的结构特性.     

等离子喷涂纳米团聚体粉末的熔化特性研究

纳米陶瓷粉末(CYZ:ZrO2-4.5wt%Y2O3-25wt?O2和YSZ:ZrO2-8wt%Y2O3)经过团聚后,采用等离子喷涂(APS)方法在GH30高温合金表面制备热障涂层(TBC).用透射电镜(TEM)、扫描电镜(SEM)、场发射显微镜(FESEM)和X射线衍射仪(XRD)对团聚体粉末在等离子焰流中的熔化情况、制备的涂层组织结构进行了分析研究.结果表明:团聚后的球形粉末经过等离子弧后对于较大的团聚体颗粒只是表层约1μm被熔化,颗粒内部仍保持原始粉末的纳米结构;制备的涂层主要由熔化结晶部分和未熔化的纳米粒子构成,熔化结晶部分晶粒尺寸为60～80nm,大于原始粉末尺寸;CYZ涂层组成相为稳定的t相和c相,涂层中分布有大量的微裂纹和闭合的孔隙;两种涂层的孔隙率分别为6.2%和7.6%.     

纳米氧化锆涂层的制备、显微结构及抗热震性能研究

利用大气等离子喷涂技术在不锈钢基体上制备了纳米氧化锆涂层.运用XRD、SEM、TEM、拉曼光谱和金相技术等分析手段对涂层的显微结构、物相组成进行了观察与分析;利用热冲击试验测试涂层的抗热震寿命.结果表明,纳米氧化锆经喷雾造粒后的颗粒粒径主要分布在15～70 μm之间,流动性好,适合等离子喷涂,粉末和涂层的物相均由四方氧化锆组成;在喷涂过程中,喷涂工艺参数(氩气流量)有规律的地影响着涂层的显微结构,进而影响涂层的抗热震性能.     

电热爆炸定向喷涂Stellite 6合金涂层

采用电热爆炸定向喷涂工艺在45号钢基体上制备stellite6合金涂层。借助光学显微镜，扫描电镜和图像分析软件等对涂层厚度均匀性、孔隙率，显微组织、晶粒度以及涂层基体界面结合情况进行了分析。借助显微硬度仪对涂层的硬度进行了测试。对不同尺寸喷涂材料所得涂层进行了比较。结果表明，两种不同尺寸喷涂材料制备的涂层组织晶粒均大大细化，涂层孔隙率都比较低；小截面积的喷涂材料制备涂层的厚度均匀性好于大截面的喷涂层；涂层与基体界面结合良好，在界面附近发生了扩散现象；涂层硬度均远远高于原始stellite6喷涂材料硬度，最高分别达到997HV和738HV，为原始硬度的2～3倍。且小尺寸喷涂材料涂层硬度高于大尺寸喷涂材料涂层硬度。     

反应等离子喷涂TiC/Fe-Ni金属陶瓷复合涂层的显微组织

采用前驱体碳化复合技术制备Ti-Fe-Ni-C系粉末,并通过反应等离子喷涂技术（RPS）原位合成并沉积了TiC/Fe-Ni基金属陶瓷复合涂层。利用XRD、SEM和EDS研究复合粉末和涂层的成分、组织结构,考察复合粉末的TiC含量及复合粉末粒度对涂层组织结构的影响。结果表明：采用前驱体碳化复合技术制备的反应喷涂复合粉末粒度均匀、无有害相生成;TiC/Fe-Ni复合涂层由不同含量TiC颗粒分布于晶粒内部而形成的晶内型复合强化片层叠加而成,基体主要为（Fe、Ni）固溶体,TiC颗粒呈纳米级;涂层TiC含量较高时,纳米级TiC颗粒弥散分布更均匀;喷涂粉末粒度较大时,片层厚度较大,孔隙率较高。     

等离子喷涂Al2O3-13％TiO2涂层微观组织形貌分析

采用微米粉末和纳米粉末,分别在45钢表面等离子喷涂Al2O3-13%TiO2涂层,测定了涂层的显微硬度和孔隙率,分析了涂层的显微组织。结果表明;微米尺寸粉末制备的Al2O3-13%TiO2涂层具有明显的层状结构;纳米尺寸粉末制备的Al2O3-13%TiO2涂层中有大量的未熔和半熔化粒子,粒子间结合紧密,涂层孔隙率小。     

电热定向爆炸制备高速钢涂层的试验研究

采用电热爆炸定向喷涂工艺在45钢基体上制备W6Mo5Cr4V2(M2)高速钢涂层。借助扫描电镜、显微硬度计分别对涂层显微组织、孔隙率、涂层基体界面结合以及涂层的硬度进行了测试。结果表明，电热爆炸定向喷涂制备的涂层组织晶粒明显细化，涂层孔隙率低；涂层与基体界面为冶金结合，且结合良好，存在一个熔合区；涂层硬度均明显高于W6MoSCr4V2喷涂材料原始硬度，最高达到954HV。     

纳米晶NiCrC涂层长时加热的显微组织和硬度变化

目的 探讨纳米晶NiCrC涂层长时高温条件下的显微组织和硬度演变规律。方法 采用超音速火焰（HVAF）喷涂低温球磨纳米晶合金粉末（液氮介质）制备了纳米晶NiCrC涂层,在650 ℃空气环境中对涂层进行总时长200 h的等温热处理。采用扫描电子显微镜、X射线衍射仪、透射电子显微镜、维氏显微硬度计等方法,对涂层样品的显微组织、物相构成、晶粒尺寸和显微硬度进行了测试分析,同时对原料粉末也进行了相同条件下的对比分析。结果 NiCrC涂层显微组织的主要特征为：纳米晶金属相基体中弥散分布着细小的碳化物颗粒。在保温过程中,纳米晶涂层发生了再结晶和晶粒长大,并伴随有合金基体的脱溶及碳化物的析出、相变和后续生长等现象。该涂层显示出优良的高温热稳定性,在650 ℃保温50 h后,晶粒平均尺寸由初始态的41 nm增长至相对稳定值约100 nm。保温后涂层的硬度总体有所提升,由初始的697HV300（15 s）先升高至最大值801HV300（15 s）,而后降至相对稳定值729HV300（15 s）左右。纳米晶粉末的组织和硬度变化特点与涂层相似。结论 在650 ℃保温过程中,纳米晶NiCrC涂层中的合金相脱溶和晶粒长大导致涂层金属相基体的软化,但细小碳化物颗粒的析出强化以及由相变（Cr7C3→Cr23C6）引起的体积分数增加,不但补偿了基体的软化,而且使涂层的整体硬度有所提高。     

直接碳化与煅烧-碳化工艺对WC-Co复合粉性能的影响

以偏钨酸铵、醋酸钴、裂解碳为原料,配置成料浆,通过喷雾干燥-氢气还原碳化(简称直接碳化法)和喷雾干燥-氮气煅烧-氢气还原碳化(简称煅烧-碳化法)制备WC-Co复合粉。对两种工艺制备粉末的性能和形貌进行对比,发现直接碳化法制备的WC-Co复合粉的颗粒在10¹00μm、平均粒度在50μm,大部分球形壳破裂,粉末仍然保持球形骨架,粉末松装密度小、流动性差;煅烧-碳化法制备的WC-Co复合粉末的颗粒度在10100μm、平均粒度在50μm,大部分球形壳破裂,粉末仍然保持球形骨架,粉末松装密度小、流动性差;煅烧-碳化法制备的WC-Co复合粉末的颗粒度在10⁵0μm、平均颗粒度25μm,粉末球形度高、流动性好。将两种工艺制备的粉末制成YG6合金,对比发现直接碳化法得到WC-Co复合粉制备成的硬质合金硬度高、晶粒度小、密度高、孔隙度低、致密度高;将两种工艺制备的粉末进行热喷涂,发现煅烧-碳化法制备的粉末热喷涂时,涂层表面致密度高、WC保留率高、硬度高。     

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.     

ZrO2纳米粉等离子喷涂层制备研究

经二次造粒的纳米ZrO2为喂料制备了等离子喷涂层。X衍射物相分析、SEM形貌观察表明．涂层主要以四方相和立方相构成，含有少量的单斜相；在喷涂过程中粉未熔化状况良好，涂层含有网状微裂纹。用金相法测定了涂层孔隙率，与普通ZrO2等离子喷涂层相比，涂层敛密度显著提高。在模拟熔炼条件下，对涂层进行了真空热震试验，涂层均能经受一次真空热震而涂层完好、单斜相含量较低、具有一定孔隙率和均匀网状微裂纹的涂层，经二次真空热震后，涂层仍处于完好状态。     

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.     

Quantitative Analysis of the Relationship Between Microstructures and Thermal Conductivity for YSZ Coatings

The thermal conductivities of as-sprayed yttria-stabilized zirconia thermal barrier coating prepared by atmospheric plasma spraying at different temperatures are investigated based on quantitative microstructural analysis. Multiple linear regression is used to develop quantitative models which describe the relationship between multiple elements such as porosity, grain boundary density, monoclinic phase content, temperature and thermal conductivity. Results reveal that the thermal conductivity of the coating is mainly determined by the porosity and grain boundary density below 300 °C and by the monoclinic phase content above 800 °C. Furthermore, based on the significance testing analysis, the confidence interval under a confidence level of 95% at different temperatures enables researchers to predict the thermal conductivity based on microstructural information.     

Impact of Impurity Content on the Sintering Resistance and Phase Stability of Dysprosia- and Yttria-Stabilized Zirconia Thermal Barrier Coatings

Dysprosia-stabilized zirconia (DySZ) is a promising candidate to replace yttria-stabilized zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high-temperature sintering behavior. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and YSZ coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 h at a temperature of 1150 °C. Samples were measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes. Phase analysis utilizing x-ray diffraction was used to determine differences in phase degradation of the coatings after heat treatment.     

Zircon-Based Ceramics Composite Coating for Environmental Barrier Coating

Studies on plasma spraying of zircon (ZrSiO₄) have been carried out by the authors as one of the candidates for an environmental barrier coating (EBC) application, and had reported that substrate temperature is one of the most important factors to obtain crack-free and highly adhesive coating. In this study, several amounts of yttria were added to zircon powder, and the effect of the yttria addition on the structure and properties of the coatings were evaluated to improve the stability of the zircon coating structure at elevated temperature. The coatings obtained were composed of yttria-stabilized zirconia (YSZ), glassy silica, whereas the one prepared from monolithic zircon powder was composed of the metastable high temperature tetragonal phase of zirconia and glassy silica. After the heat treatment over 1200 °C, silica and zirconia formed zircon in all coatings. However, coatings with higher amounts of yttria exhibited lower amounts of zircon. This resulted in the less open porosity of the coating at elevated temperature. These yttria-added coatings also showed good adhesion even after the heat treatment, while monolithic zircon coating pealed off.     

Ceramic nanocomposites obtained by sol–gel coating of submicron powders

MgAl₂O₄–ZrO₂ nanocomposites were fabricated by conventional sintering of composite powders obtained by sol–gel coating of a submicron spinel powder. In the composite powder the zirconia grains remain narrow sized and completely tetragonal even after being heat treated at temperatures where a free xerogel is completely monoclinic. The sintered material exhibits a dense, fine and highly homogeneous microstructure. The zirconia nanoparticles are located at both inter- and intragranular positions and exhibit heteroepitaxial relationships with the surrounding crystals. Tetragonal zirconia seems to be stabilised by an interface effect. Both the scale of the microstructure and the fraction of intragranular grains were controlled by adjusting the mean grain size of spinel grains before coating and sintering conditions.     

水热法制备稳定氧化锆纳米粉体

目的制备分散性好、粒径分布窄的稳定氧化锆纳米粉体。方法采用水热法制备氧化锆纳米粉体,考察水热时间、p H值、温度和有机添加剂丙三醇,对氧化锆粉体颗粒粒径、结晶度及稳定性的影响。通过XRD和SEM分析技术对不同条件下制备的样品进行表征。结果结晶度随着水热反应温度的升高而提高,形核速率在250℃时快速增加,粒径在150~250℃出现先长大后减小的规律。反应溶液的p H值影响样品的结晶度,通过调节溶液p H值可以减小粉体颗粒之间的团聚,改善粉体的分散性。水热反应进程越充分,样品的平均粒径越大。加丙三醇后,在反应条件为200℃、p H=10、t=12 h时制备钇掺杂量3%的氧化锆粉体,于1000℃煅烧12 h,得到分散性好、粒径分布窄的单立方相纳米氧化锆粉体颗粒。结论通过设定水热法反应温度、p H值、时间,可以制备粒径可控的稳定氧化锆纳米粉体,且钇掺杂可有效提高氧化锆的稳定性。加入丙三醇可以有效地改善粉体的分散性和稳定性,煅烧稳定氧化锆纳米粉体可以有效减小粉体粒径分布和提高粉体的结晶度。     

多孔YSZ涂层的制备和可磨耗性

采用等离子喷涂方法在Ni718合金表面制备氧化钇稳定氧化锆（YSZ）涂层,通过在YSZ喷涂粉末中分别加入10%,30%和50%（质量分数,%）表面包覆TiO₂的聚苯酯材料,涂层平均孔隙率从原来的2.1%分别提高到12.3%,28.5%和29.7%,孔隙的平均直径从原来的4.2 μm分别变为14.4,18.5和25.4 μm.随着孔隙的增多,涂层的表面洛氏硬度下降,同时涂层在刮磨过程中的摩擦力和摩擦系数下降.当孔隙率由2.1%上升到30%左右时,涂层在刮磨过程中的磨耗质量上升3倍左右,相对应的转动销质量损失下降约50%.结果表明,孔隙率的提高使得涂层的可磨耗性上升.