反应等离子喷涂制备FeAl2O4-A12O3-Fe复合涂层的研究

以铝粉和氧化铁粉为原料，制备出适于等离子喷涂的复合团聚粉体；并采用反应等离子喷涂技术制备出FeAl2O4-A12O3-Fe复合涂层，用SEM和XRD分析了复合涂层的组织结构。结果表明：反应等离子喷涂得到了以层状基体相FeAl2O4与硬质相Al2O3为骨架，球状Fe相弥散分布于基体上的复合涂层。     

反应等离子喷涂制备FeAl2O4-Al2O3-Fe复合涂层的研究

以铝粉和氧化铁粉为原料,制备出适于等离子喷涂的复合团聚粉体;并采用反应等离子喷涂技术制备出FeAl2O4-Al2O3-Fe复合涂层,用SEM和XRD分析了复合涂层的组织结构.结果表明反应等离子喷涂得到了以层状基体相FeAl2O4与硬质相Al2O3为骨架,球状Fe相弥散分布于基体上的复合涂层.     

Microstructure and properties of flame sprayed tungsten carbide coatings

This article reports on feasibility experiments carried out with oxy-acetylene spray system with various oxygen to fuel ratios using two different tungsten carbide powders and powder feeding methods, to evaluate the newly developed fused WC, synthesised by transferred arc thermal plasma method. Transferred arc thermal plasma method is more economical and less energy intensive than the conventional arc method and results in a fused carbide powder with higher hardness. The microstructure and phase composition of powders and coatings were analysed by optical and scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Carbon content of the powders and coatings were determined to study the decarburisation of the material during spraying process. Coatings were also characterised by their hardness and abrasive wear. The effects of metallurgical transformation and phase content are related to wear performance. The results demonstrate that the powders exhibit various degree of phase transformation during the spray process depending on the type of powder, powder feeding and spray parameters. The carbon loss during the spray process in excess of 45% resulted in reduced hardness and wear resistance of the coatings. Coatings with high amount of WC and W₂C along with FeW₃C showed higher wear resistance. Thus, coatings of high wear resistance can be produced using fused tungsten carbide powder with WC and W₂C phases, which can be economically synthesised by thermal plasma transferred arc method.     

TiB2陶瓷粉末纳米化改性及其增强环氧复合涂层的制备与表征

低温条件下,以钛酸丁酯为原料,采用胶溶-回流方法在TiB₂粉体表面包覆纳米TiO₂颗粒。通过SEM、XRD、BET等分析检测方法对复合颗粒的表观形貌、包覆层相成分、比表面积等进行表征。结果显示,纳米TiO₂颗粒均匀离散地包覆在TiB₂粉体表面,包覆层主要为锐钛矿型相,TiB₂粉体纳米化改性后复合颗粒的表面粗糙度显著增加,比表面积较包覆前提高35倍以上。将包覆后的TiB₂粉体引入环氧树脂制备耐磨复合涂层,测得其磨损失重仅为包覆前复合耐磨涂层的50%,其耐磨性显著提高,并初步分析了复合耐磨涂层的摩擦磨损性能、磨损形貌及耐磨机理。     

以沥青为前驱体制备TiC/FeCrNi反应火焰喷涂复合涂层

以钛铁粉、CrFe粉、羰基镍粉和碳的前驱体（石油沥青）为原料,通过前驱体碳化复合技术制备了Ti-Fe-Cr-Ni-C反应喷涂复合粉末,并通过普通火焰喷涂成功地合成与沉积了TiC/FeCrNi复合涂层.采用XRD和SEM对喷涂粉末和涂层的相组成和显微结构进行了分析,同时对涂层耐磨性能进行了对比研究.研究结果表明：采用前驱体碳化复合技术制备的Ti-Fe-Cr-Ni-C反应喷涂复合粉末粒度均匀、无有害相生成;所制备的TiC/FeCrNi复合涂层由不同含量TiC颗粒分布于金属基体内部而形成的复合强化片层叠加而成,TiC颗粒呈纳米级;基体由（Fe,Cr）和Cr0.19Fe0.7Ni0.11两相组成;相同条件下,所获TiC/FeCrNi复合涂层磨损体积大约是常规火焰喷涂Ni60涂层的1/8.     

WC-Co复合粉末的原位合成及于硬质合金涂层制备中的应用

目的为解决超细/纳米WC-Co热喷涂时易于脱碳等瓶颈问题,制备具有高的硬度、断裂韧性、耐磨性和表面质量等优异综合性能的超细及纳米结构硬质合金涂层,并推广其在工业领域中的应用。方法以原位合成技术批量制备的超细/纳米WC-Co复合粉末为原料,利用团聚造粒技术制备得到具有高球形度和致密性,并保持原有超细/纳米结构的喷涂喂料粉末,利用超音速火焰喷涂工艺制备低脱碳、高致密的超细结构WC基涂层。结果降低喂料粉末孔隙度可有效减少涂层中W2C等脱碳相的含量,在优化工艺下制备的超细结构WC基涂层的硬度达到1450HV0.3以上,韧性相对于常规微米结构涂层提高40%以上,在两种载荷和磨料条件下均表现出更高的耐磨性。结论利用原位反应技术批量合成的超细/纳米WC-Co复合粉制备的硬质合金涂层具有优良的综合性能,可应用于对涂层的硬度、耐磨性、强韧性配合和表面质量有较高要求的工况。     

Post-treatment of thermal spray coatings on magnesium

Magnesium alloys have a beneficial combination of high strength to weight ratio, good machinability and high recycling potential. Despite this, the application of magnesium still is behind that of other constructive materials mainly due to low wear and corrosion resistance. For more demanding applications, a large amount of surface treatment methods are developed to overcome this problem. Thermal spraying is an efficient and flexible method of coating deposition and is widely used for protection of different materials against corrosion and wear. Nevertheless, the bonding of thermal spray coatings on magnesium alloys is not sufficient, so the following post-treatment processes are needed. One of such possibilities is high energy beam treatment of thermally sprayed coatings. During the heat treatment of magnesium substrates with coating the remelting of coating and a thin surface layer of substrate occurs. Depending on the combination of applied coating system and treatment method, different processes can be realised in modified layers: the alloying of magnesium substrate with other elements to improve corrosion properties, redistribution of hard particles from composite coating and new phases formation during the processing to improve the wear resistance of magnesium alloys. In the present work some examples concerning the laser and electron beam treatment of aluminium based composite coatings as well as infra red irradiation of zinc based coatings are described. Coatings are deposited on magnesium substrates (AM20, AZ31, AZ91) by arc spraying with Zn, ZnAl4 and ZnAl15 solid wires and cored wires in aluminium core with powder filling containing different hard particles, such as boron, silicon and tungsten carbide or titanium oxide. Remelting of thermal spray coatings is carried out by means of continuous irradiation of СО₂-laser in nitrogen or argon atmosphere, electron beam in vacuum and focused tungsten halogen lamp line heater in atmosphere. Microstructure of sprayed coatings as well as that of modified surface layers is investigated by metallographic methods. Corrosion properties are estimated by electrochemical measurements. Abrasion wear resistance of the modified layers is determined by scratch test, corundum grinding disk test and Rubber wheel test. It is shown that all methods applied for processing of thermal spray coatings lead to formation of modified surface layers in magnesium substrate with improved wear and corrosion properties. Different mechanisms of microstructure formation such as redistribution of chemical composition of composite coating components, partial remelting of hard phase particles, and new phases formation are discussed. Electrochemical behaviour of modified surface layers is mostly improved due to alloying, homogenization of element distribution and strong decrease of as-sprayed coating porosity. Abrasion wear resistance of processed magnesium substrates strongly depends on the microstructure and usually is 5 to 20 times higher compared with base material.     

高导热高绝缘导热硅脂的制备及性能表征

高导热硅脂作为一种热界面材料,可以显著地减小因接触空隙而产生的热阻,提高散热效果。通过采用自制的氮化硅、氮化铝、氧化铝等陶瓷粉体来代替传统的金属粉体作为导热填料,制备出高绝缘高导热的导热硅脂。研究了陶瓷粉体种类、添加量以及表面改性剂对导热硅脂热导率的影响规律。采用热阻测试仪、AMD、Inter主板测试平台、耐压测试仪等表征了导热硅脂的导热和绝缘性能。并对实验结果进行了理论分析。     

Powder/processing/structure relationships in WC-Co thermal spray coatings: A review of the published literature

Thermally sprayed coatings based on tungsten carbide are widely used but not yet fully understood, particularly with regard to the chemical, microstructural, and phase changes that occur during spraying and their influence on properties such as wear resistance. The available literature on thermally sprayed WC-Co coatings is considerable, but it is generally difficult to synthesize all of the findings to obtain a comprehensive understanding of the subject. This is due to the many different starting powders, spray system types, spray parameters, and other variables that influence the coating structures and cause difficulties when comparing results from different workers. The purpose of this review is to identify broad trends in the powder/processing/structure relationships of WC-Co coatings, classified according to powder type and spray method. Detailed comparisons of coating microstructures, powder phase compositions and coating phase compositions as reported by different researchers are given in tabular form and discussed. The emphasis is on the phase changes that occur during spraying. This review concerns only WC-12% Co and WC-17% Co coatings, and contrasts the coatings obtained from the cast and crushed, sintered and crushed, and agglomerated and densified powder types. Properties such as hardness, wear, or corrosion resistance are not reviewed here.     

High-temperature tribological properties of plasma-sprayed metallic coatings containing ceramic particles

Plasma-sprayed metal-base coatings containing ceramic particles were considered for high-temperature sealing of a moving metal component with a dense silica-base ceramic preheated at 800 ‡C. Selected metal powders (NiCoCrAlY, CuNi, CuNiIn, Ag, Cu) and ceramic particles (boron nitride, Zeta-B ceramic) were agglomerated to form suitable spray powders. Plasma-sprayed composite coatings and reference materials were tested in a modified pinion-disk apparatus in which the stationary disk consisted of a dense silica-base ceramic piece initially heated at 800 ‡C and allowed to cool during tests. The influence of single exposure and repeated contact with ceramic material on coefficient of friction, wear loss, and damage to the ceramic piece was evaluated.     

Microstructure and performance of WC-Co-Cr coating with ultrafine/nanocrystalline structures

The WC-lOCo-4Cr composite powder was synthesized firstly. Then the composite powder was agglomerated to prepare thermal spraying feedstock. The ultrafine/nanostructured WC-lOCo-4Cr coating was prepared by high velocity oxygen fuel thermal spraying. The phase constitution, elemental distribution and microstructure of the coating were characterized by X-ray diffraction and transmission electron microscopy, respectively. The wear resistance and corrosion resistance of the prepared composite coating were tested. The results show that the main phases of the coating include WC, binding phase with partial amorphous structure, with a little W_2C and Co(Cr)coexisting. The distributions of Co and Cr elements from the phase boundary to the eutectic area then to Co zone were analyzed quantitatively. The mechanisms for the formation of the microstructure and effects of Cr on the performance of the composite coating are proposed.     

Thermal Spray Coatings Engineered from Nanostructured Ceramic Agglomerated Powders for Structural,Thermal Barrier and Biomedical Applications: A Review

Thermal spray coatings produced from nanostructured ceramic agglomerated powders were tailored for different applications, some of which required almost completely opposite performance characteristics (e.g., anti-wear and abradable coatings). The influence of nanostructured materials on important areas, such as, thermal barrier coatings (TBCs) and biomedical coatings was also investigated. It was determined that by controlling the distribution and character of the semi-molten nanostructured agglomerated particles (i.e., nanozones) embedded in the coating microstructure, it was possible to engineer coatings that exhibited high toughness for anti-wear applications or highly friable for use as abradables, exhibiting abradability levels equivalent to those of metallic-based abradables. It is shown that nanozones, in addition to being very important for the mechanical behavior, may also play a key role in enhancing and controlling the bioactivity levels of biomedical coatings via biomimetism. This research demonstrates that these nanostructured coatings can be engineered to exhibit different properties and microstructures by spraying nanostructured ceramic agglomerated powders via air plasma spray (APS) or high velocity oxy-fuel (HVOF). Finally, in order to present readers with a broader view of the current achievements and future prospects in this area of research, a general overview is presented based on the main papers published on this subject in the scientific literature.     

Crack initiation and propagation of galvanized coatings hot-dipped at 450 °C under bending loads

Crack initiation and propagation behaviors in the intermetallic layers of galvanized coatings subjected to bending loads are characterized and numerically simulated. Coating structure of galvanized steel prepared by hot dipping at 450 °C is a laminate composite consisting of δ, ζ, and η phases, with an infinitesimal layer between the coating and steel article speculatively representing a Γ phase. The specimens were deformed in a four-point bending configuration, and the evolution of cracks was investigated as a function of bending angles. Through-cracks were found to develop in the δ layer of the coatings after thermal cooling due to thermal stresses and propagate toward the outer surface under increments of bending loads. Finite element simulations of galvanized steels were subsequently developed with an initial crack tip located in the δ layer to determine the controlling parameters of the crack propagation and to assess the coatings' fracture parameter, critical far field stress, and stress distributions. The analysis highlights the enhancement of fracture resistance of the galvanized coatings owing to the presence of the ζ layer.     

Comparison of atmospheric plasma sprayed anode layers for SOFCs using different feedstock

Atmospheric plasma spraying (APS) is a cost-effective way to produce solid oxide fuel cell (SOFC) components. When using APS, therefore, sinter steps can be avoided, which is essential once a metallic support is used for the SOFC. Several properties are required regarding the microstructure of an optimized anode layer. Here, gas permeability, electrochemistry, electronic conductivity, coefficient of thermal expansion, as well as thermal shock resistance have to be considered. Different types of powder feedstock were investigated to develop an atmospheric plasma sprayed anode layer: (a) NiO or Ni together with YSZ as starting materials, (b) agglomerates in which NiO and YSZ are already mixed on a submicrometer range, (c) blended NiO/YSZ powder, and (d) separate injection of the individual NiO and YSZ powders, respectively, into the plasma by two separate powder lines. The performance of APS anodes are measured in single fuel-cell tests. Anode layers sprayed by a separate injection of the individual NiO and YSZ powders into the plasma show the best results. This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, OH, 2006.     

粉末结构对HVOF喷涂WC-Co涂层组织性能的影响

选用4种不同WC尺度的WC-12Co粉末作为初始喂料,通过超音速火焰喷涂系统(HVOF)制备了涂层。考察了不同粉末结构对涂层沉积过程的脱碳行为和涂层组织性能的影响。结果表明:WC颗粒尺寸减小加剧了涂层脱碳行为,涂层中W2C含量增加,粘结相非晶化现象明显,涂层硬度增加,但是当WC颗粒尺寸减小到纳米尺度时,韧性下降。双峰结构涂层表现出最好的韧性同时兼备较高的硬度。     

添加Zn对自反应淬熄法制备Mn-铁氧体空心微珠相结构与性能的影响

采用自反应淬熄法制备了Mn-铁氧体复合空心微珠,分析了自蔓延反应体系中添加Zn元素对制备空心微珠的形貌、相结构和电磁参数的影响。结果表明,制备的粉末大部分为球状空心微珠,粒径在微米范围,少量自蔓延反应不完全的团聚颗粒未能球化,形成不规则颗粒。Zn的引入使得微珠成分转变为以Mn0.5Zn0.5Fe2O4铁氧体为主,提高了Mn-铁氧体复合空心微珠的微波电磁损耗,使吸收峰向高频移动。     

Recycled hard metal-base wear-resistant composite coatings

The abrasion-erosion wear resistance of composite coatings from self-fluxing Ni-base alloy and WC-Co hard metal powders is evaluated. The resistance of thermal sprayed and melted NiCrSiB-(WC-Co) coatings was found to be markedly higher than that of NiCrSiB and slightly higher than that of comparative welded coatings. Microstructural and surface analyses were used to describe the coatings and the wear damage. Based on the principles of creating wear-resistant coatings and on experimental studies of wear resistance, high wear-resistant, composite NiCrSiB-(WC-Co) coatings were fabricated. These coatings exhibited 300% higher wear resistance than 0.45% C steel.     

等离子喷涂Al2O3与ZrO2复合热障涂层的高温性能

采用等离子喷涂(PS)方法，在GH536高温合金基材上制备了传统的双层热障涂层(TBCs)和2种含有Al2O3与ZrO2陶瓷复合层的3层热障涂层。传统TBC8结构为Ni22Cr10AlY合金连接层和8％Y2O3部分稳定的ZrO2(8YPSZ)陶瓷顶层；3层TBCs中分别采用置于8YPSZ陶瓷层内层及外层的Al2O3与8YPSZ复合层。3种类型试样的100h。1050℃静态氧化试验及1050℃热震试验结果表明：3层涂层较双层涂层的氧化阻力提高，双层涂层的热震阻力最佳，氧化阻力最差。不同复合层形式试样的热振失效方式和寿命也有差别，复合层置于陶瓷层外层热震寿命略高，但100h氧化增重有明显提高，抗氧化性降低。     

Plasma spraying of functionally graded yttria stabilized zirconia/NiCoCrAlY coating system using composite powders

Pre-alloyed and plasma spheroidized composite powders were used as the feedstock in the plasma spraying of functionally graded yttria stabilized zirconia (YSZ)/NiCoCrAlY coatings. The ball milling parameters of the composite powders and the plasma spraying parameters for preparing functionally graded materials (FMGs) coatings were optimized to obtain the best performance for the thermal barrier coatings (TBCs). Microstructure, physical, mechanical, and thermal properties of YSZ/NiCoCrAlY FGMs coatings were investigated and compared with those of traditional duplex coatings. Results showed that the advantages of using pre-alloyed composite powders in plasma spraying were to ensure chemical homogeneity and promote uniform density along the graded layers. Microstructure observation showed the gradient distribution of YSZ and NiCoCrAlY phases in the coating, and no clear interface was found between two adjacent different layers. Oxidation occurred during plasma spray and the resultant aluminum oxide combines with YSZ in a wide range of proportions. The bond strength of functionally graded coatings was about twice as high as that of the duplex coatings because of the significant reduction of the residual stresses in the coatings. The thermal cycling resistance of functionally graded coating was much better than that of duplex coating.     

氧化锆粉体的制备及其在热障涂层中的应用

分别描述了纳米氧化锆粉体与空心球氧化锆粉体的制备工艺，分析了不同工艺影响氧化锆产物形态、结构、粒度等方面的因素，并将2种粉末制备的涂层分别与传统微结构涂层进行性能对比。在分析由不同氧化锆粉末制备而成的涂层性能时，除了工艺参数外，更多的是考虑初始氧化锆粉末对涂层性能所带来的影响。期待在未来的研究中，能够优化现有或者探索出更优异的制粉工艺，研究出性能更加优良的新型粉末，以期能够提高热障涂层的性能，满足高精尖领域在未来的使用需求。最后，针对不同制粉工艺及不同粉末制备涂层的发展方向进行了展望。