Recent Developments in Suspension Plasma Sprayed Titanium Oxide and Hydroxyapatite Coatings

The paper aims at reviewing of the recent studies related to the development of suspension plasma sprayed TiO₂ and Ca₅(PO₄)₃OH (hydroxyapatite, HA) coatings as well as their multilayer composites obtained onto stainless steel, titanium and aluminum substrates. The total thickness of the coatings was in the range 10 to 150 μm. The suspensions on the base of distilled water, ethanol and their mixtures were formulated with the use of fine commercial TiO₂ pigment crystallized as rutile and HA milled from commercial spray-dried powder or synthesized from calcium nitrate and ammonium phosphate in an optimized reaction. The powder was crystallized as hydroxyapatite. Pneumatic and peristaltic pump liquid feeders were applied. The injection of suspension to the plasma jet was studied carefully with the use of an atomizer injector or a continuous stream one. The injectors were placed outside or inside of the anode-nozzle of the SG-100 plasma torch. The stream of liquid was tested under angle right or slightly backwards with regard to the torch axis. The sprayed deposits were submitted to the phase analysis by the use of x-ray diffraction. The content of anatase and rutile was calculated in the titanium oxide deposits as well as the content of the decomposition phases in the hydroxyapatite ones. The micro-Raman spectroscopy was used to visualize the area of appearance of some phases. Scratch test enabled to characterize the adhesion of the deposits, their microhardness and friction coefficient. The electric properties including electron emission, impedance spectroscopy, and dielectric properties of some coatings were equally tested.     

Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings

Fine, home-synthesized, hydroxyapatite powder was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto a titanium substrate. The deposition process was optimized using statistical design of 2 ⁿ experiments with two variables: spray distance and electric power input to plasma. X-ray diffraction (XRD) was used to determine quantitatively the phase composition of obtained deposits. Raman microscopy and electron probe microanalysis (EPMA) enabled localization of the phases in different positions of the coating cross sections. Transmission electron microscopic (TEM) study associated with energy-dispersive x-ray spectroscopy (EDS) enabled visualization and analysis of a two-zone microstructure. One zone contained crystals of hydroxyapatite, tetracalcium phosphate, and a phase rich in calcium oxide. This zone included lamellas, usually observed in thermally sprayed coatings. The other zone contained fine hydroxyapatite grains that correspond to nanometric and submicrometric solids from the suspension that were agglomerated and sintered in the cold regions of plasma jet and on the substrate.     

等离子喷涂羟基磷灰石涂层的化学不均匀性和浸泡行为

利用X射线衍射仪（XRD）、电子探针（EPMA）等检测手段,对纯钛表面等离子喷涂羟基磷灰石（HA）涂层的化学不均匀性和浸泡行为以及热处理对涂层化学不均匀性的影响进行了研究.结果表明,喷涂后的涂层中存在化学不均匀性,原始颗粒越小不均匀性越严重;去离子水浸泡后,涂层表面析出Ca2P2O7等化合物,浸泡时间越长、原始颗粒越小的涂层析出物越多;热处理能使非晶相和分解相重新生成HA,提高涂层结晶度而消除非均匀现象.     

纳米 Al2 O3 等离子喷涂涂层的制备及性能分析

目的对比研究微/纳米Al2O3等离子喷涂涂层的组织、力学及摩擦磨损行为。方法以纳米Al2O3粉末为原料,利用喷雾干燥法制备出粒径分布在35~75μm的喷涂喂料,采用等离子喷涂技术在20钢基体上制备纳米Al2O3涂层。采用商用微米Al2O3喂料,以相同的喷涂工艺制备出微米Al2O3涂层。对粉末、涂层的显微结构及涂层的磨损形貌进行表征,对比分析两种涂层的组织、力学性能和摩擦磨损行为。结果与微米Al2O3涂层相比,纳米Al2O3涂层粒子间结合更为致密,使得其结合强度和显微硬度得到大幅度提高。在载荷750 g,转速1000 r/min的条件下,微米Al2O3涂层的摩擦系数为0.41,而纳米Al2O3涂层仅为0.34,并且摩擦系数值的波动幅度更为稳定。在不同转速下,纳米Al2O3涂层的磨损率均降低明显。结论纳米Al2O3等离子喷涂涂层组织致密,表现出了较好的力学性能和耐磨性。     

碱液环境中等离子喷涂羟基磷灰石涂层的电极化后处理研究

采用碱液环境中电极化处理法（PAS）和水蒸气处理法（wVT）对等离子喷涂羟基磷灰石涂层进行后处理。采用XRD，FTIR，SEM，接触角测量仪等测试手段对涂层进行表征。结果表明，PAS和WVT都能提高涂层的结晶度和结构完整性，促使涂层中的杂相向羟基磷灰石转化，但PAS比WVT转化得更完全。PAS与WVT两种后处理方法对涂层原有的表面形貌影响都不大。与WVT相比，PAS处理后的涂层亲水性更好、表面能更高，且涂层表面上产生了更多的负电荷。PAS处理后的涂层与基体材料的结合强度略低于WVT，但仍然达到了ISO13779-2：2000标准的相关要求。     

Plasma Sprayed PMMA Coatings on Steel

PMMA coatings have been applied to steel by plasma spraying. The work shows that the polymer decomposition temperature is a function of the particle residence time in the plasma and is much higher than in conventional polymer processing. The analysis indicates that realistic prediction of the temperature profiles of in-flight polymer particles can only be obtained by using this dynamic decomposition temperature. The process model predicts that only the surface layers of the polymer feedstock particles undergo significant decomposition under optimized spraying conditions.     

等离子喷涂结构涂层研究

介绍了等离子喷涂的原理及特点;综述了等离子喷涂结构涂层的研究进展,包括耐磨涂层、热障涂层、耐蚀涂层;介绍了等离子喷涂结构涂层的复合处理技术;展望了等离子喷涂结构涂层的发展前景。     

钛基材上电化学沉积羟基磷灰石

通过电沉积法在经过阳极氧化的钛基材表面沉积磷酸钙盐涂层,再经碱热处理使磷酸钙涂层转变为羟基磷灰石涂层。扫描电镜(SEM)观察了阳极氧化后生成的TiO2纳米管的微观结构,以及生成的羟基磷灰石的形貌。X射线衍射仪(XRD)分析了涂层的相组成,同时测定了涂层与基体的结合强度。试验结果表明:电沉积涂层CaHPO4·2H2O经碱处理后转变为羟基磷灰石;电沉积添加双氧水与钛基材经过阳极氧化后使得涂层与基体结合强度有所提高。模拟体液浸泡试验表明涂层具有良好的生物活性。     

电化学沉积法制备钛基HA涂层

在钛基材表面获得羟基磷灰石（HA）涂层以改善钛与生物体的相容性，本项工作采用电沉积的方法在阳极氧化处理过的钛基体上制备了羟基磷灰石涂层。用扫描电子显微镜（SEM）、X射线衍射（XRD）等手段对涂层进行了表征。试验结果表明：电沉积初期的羟基磷灰石涂层呈多孔层片状：随电压、时间、电解液浓度的增大，涂层变厚，层片呈花瓣状发散排列：对基体阳极氧化处理有助于提高钛基与涂层的结合强度。     

Properties of Induction Plasma Sprayed Iron Based Nanostructured Alloy Coatings for Metal Based Thermal Barrier Coatings

Metal-based thermal barrier coatings (MBTBCs) have been produced using high frequency induction plasma spraying (IPS) of iron-based nanostructured alloy powders. The study of MBTBCs has been initiated to challenge issues associated with current TBC materials such as difficult prediction of their “in-service” lifetime. Reliability of TBCs is an important aspect besides the economical consideration. Therefore, the study of MBTBCs, which should posses higher toughness than the current TBC materials, has been initiated to challenge the mechanical problems of ceramic-based TBCs (CBTBCs) to create a new generation of TBCs. The thermal diffusivity (TD) (α) properties of the MBTBCs were measured using a laser flash method, and density (ρ) and specific heat (C _p) of the MBTBCs were also measured for their thermal conductivity (k) calculation (k = αρ C _p).     

大气与真空等离子体喷涂钨涂层的比较

利用等离子体喷涂技术在铜合金基体上制备1mm的钨涂层,并对大气和真空等离子体喷涂钨涂层性能进行比较。结果表明,真空喷涂钨涂层气孔率低、传热能力高、杂质含量低、结合强度高,热负荷性能好。与大气等离子体喷涂钨涂层相比,真空喷涂技术更适合应用到核聚变实验装置内壁上。     

[例23]钛合金植入体等离子体表面改性

钛及其合金具有比重小、弹性模量与人体骨组织较匹配以及优良的耐腐蚀性和生物相容性等优点,是目前应用最为广泛的生物医用金属材料,常用作人工骨、人工关节、种植牙、种矫形组件等。但相对人体组织而言,钛植入体仍然是外体材料,不能完全为人体接受,其生物惰性、金属离子的释放和磨粒的形成,都会影响到植入体的正常使用     

Process Design and Monitoring for Plasma Sprayed Abradable Coatings

Abradable coatings in compressor and high-pressure stages of gas turbines must provide specific hardness and porosity values to achieve an optimal cut-in of the blade tips. A fractional factorial experimental plan was designed to investigate the influence of the plasma spraying parameters argon flow rate, current, spraying distance and powder feed rate on these properties of magnesia spinel. Based on the results, magnesia spinel coatings with low (~400 HV_0.5), medium (~600 HV_0.5) and high hardness (~800 HV_0.5) could be reliably manufactured. Further incursion rig tests confirmed the dependence of the rub-in behavior and abradability on the coating characteristics and process parameters, respectively. Process monitoring was also applied during plasma spraying of magnesia spinel abradables on batches of turbine components. The recorded particle characteristics and coating properties showed a good reproducibility of the spraying process.     

等离子喷涂陶瓷涂层后氧化处理的研究

对比研究了后氧化处理、封孔和退火、真空退火对大气等离子喷涂 (Al/Ni Cr2 O3 )陶瓷涂层硬度、结合强度等性能的影响。结果表明 ,合理的后氧化能够明显改善涂层性能 ,且氧的扩散是发挥作用的重要因素之一。     

High-Velocity Suspension Flame Sprayed (HVSFS) Hydroxyapatite Coatings for Biomedical Applications

In this study, hydroxyapatite (HAp) coatings were deposited on Ti plates by the high-velocity suspension flame spraying (HVSFS) technique. The process characteristic, the microstructure and phase composition of the coatings are significantly influenced by the solvent and by the design of the combustion chamber (CC) of the HVSFS torch. Water-based suspensions always lead to fairly low surface temperatures (≈350 °C), deposition efficiencies <40%, and produce coatings with low amount of crystalline HAp, which tend to dissolve very rapidly in simulated body fluid (SBF) solutions. DEG-based suspensions, when sprayed with properly-designed CCs, produce deposition efficiencies of 45-55% and high surface temperatures (550-600 °C). In these coatings, the degree of crystallinity increases from the bottom layer to the top layer, probably because the increasingly large surface temperature can eventually favour re-crystallisation of individual lamellae during cooling. These coatings are much more stable in SBF solutions.     

等离子喷涂制备纳米结构涂层研究进展

等离子喷涂制备的纳米结构涂层在耐热、耐磨、耐蚀、生物相容性等方面比传统微米级涂层具有更优良的性能,从而在军事以及民用工业等领域得到了广泛应用。本文介绍了纳米结构喂料的制备方法,评述了等离子喷涂制备纳米涂层的研究进展,并对等离子喷涂纳米结构涂层的研究和发展进行展望。     

铜基体上等离子体喷涂钨涂层性能研究

介绍了铜基体上等离子喷涂1 mm钨涂层核聚变试验装置壁材料的制备,并对真空和大气等离子体喷涂钨涂层性能进行了比较研究,内容主要包括微观形貌、气孔率、杂质含量、结合强度和热负荷性能.结果表明,气孔率和氧杂质含量差异是大气和真空等离子体喷涂钨涂层热负荷性能差异的主要原因.