热喷涂纳米结构涂层的研究

纳米材料具有许多优异的特性,利用热喷涂技术制备纳米结构涂层是一种应用纳米材料的有效办法.文中介绍了纳米结构涂层喷涂材料的制备,包括液体喂料制备纳米材料、纳米粉末材料和纳米药芯丝材的制备,以及热喷涂制备纳米结构涂层的种类,纳米结构涂层的种类包括纳米结构陶瓷涂层、金属-陶瓷纳米复合涂层和金属纳米结构涂层.简要介绍了制备这些涂层所采用的工艺方法,以及涂层的结构和性能.指出了目前热喷涂制备纳米结构涂层存在的问题,并对其应用和发展前景作了展望.     

一般问题/焊接科学和技术的发展及前景

纳米材料具有许多优异的特性，利用热喷涂技术制备纳米结构涂层是一种应用纳米材料的有效办法。介绍了纳米结构涂层喷涂材料的制备，包括液体喂料制备纳米材料、纳米粉末材料和纳米药芯丝材的制备，以及热喷涂制备纳米结构涂层的种类，其中包括纳米结构陶瓷涂层、金属一陶瓷纳米复合涂层和金属纳米结构涂层。[第一段]     

超音速火焰喷涂（HVAF）Ni-WC合金涂层组织与显微硬度分析

0前言 20世纪90年代研制成功的超音速火焰喷涂（HVOF）技术是热喷涂领域一次革命性的进步,与等离子喷涂技术相比,HVOF可以大幅度提高热喷涂涂层的结合强度,并且同时减小甚至消除了涂层中的氧化物含量.     

超音速火焰喷涂纳米结构WC-12Co涂层耐泥沙冲蚀性能研究

采用超音速火焰喷涂(HVOF)分别制备了纳米结构、双峰结构及微米结构WC-12Co金属陶瓷复合涂层,比较了不同结构WC-12Co涂层的组织结构及显微硬度,进行了不同结构WC-12Co涂层和Ni60喷熔层的泥浆冲蚀磨损试验,并探讨了它们的泥浆冲蚀机理.结果表明:采用超音速火焰喷涂制备的纳米结构及双峰结构WC-12Co涂层结构致密,涂层显微硬度明显高于微米结构WC-12Co涂层;与微米结构WC-12Co涂层相比,纳米结构和双峰结构WC-12Co涂层具有更优良的抗泥浆冲蚀性能,其耐泥浆冲蚀性能分别提高了50%及20%以上.     

超音速火焰喷涂碳化物涂层预处理工艺研究

0引言 超音速火焰喷涂技术（HVOF）是利用经特殊设计的超音速喷嘴等特殊结构的喷枪,使用高压和高能燃料,使喷涂的粉末粒子高速喷射到工件表面,形成高结合强度涂层的一种技术。20世纪90年代以来,美国等西方发达国家,用超音速火焰喷涂技术制备WC—Co材料耐磨涂层,标志着世界热喷涂工艺上一项重要的技术诞生。由于HVOF喷涂火焰温度并不高,且对粉末的加热时间很短,可以防止粉末的过分氧化、烧损、蒸发和分解,制备的涂层具有很好的耐磨和抗氧化性能,所以备受航空航天界的青睐,并很快得到了应用,如飞机发动机的涡轮叶片、发动机密封件、飞机起落架等易磨耗件等等。     

超音速火焰喷涂TiCrAl-ZrO_2热障涂层组织及性能的研究

在20钢基体上利用超音速火焰喷涂(HVOF)技术制备TiCrAl-ZrO2热障涂层,并通过扫描电镜、X射线衍射仪、显微硬度计、图像分析仪以及万能拉伸机对涂层的组织与性能进行了分析和研究。结果表明:HVOF制备的TiCrAl-ZrO2热障涂层结构致密,硬度高,空隙率低,涂层与基体之间结合良好。     

超音速火焰喷涂技术在模具修复中的应用

采用超音速火焰喷涂(HVOF)技术,在Cr12MoV模具钢表面制备了纳米结构的WC_12Co金属陶瓷涂层,对涂层的组织、结合强度、剪切强度以及抗冲击性能进行了测试研究。测得涂层平均剪切强度达150.8 MPa,涂层的结合强度大于80 MPa,涂层硬度高于1000 HV。试样涂层在冲击1 000次时,表面形貌以表面蚀坑为主,涂层表面出现龟壳状裂纹。运用HVOF技术对某冷挤压模修复后,使用效果良好。     

超音速火焰喷涂枪的冲蚀磨损研究进展

超音速火焰喷涂(HVOF)技术是热喷涂技术中的重要组成部分,也是表面强化的重要方法之一。超音速火焰喷涂因其所制备的涂层质量优良,可以说是最具发展前途的热喷涂技术。作为超音速火焰喷涂系统的子系统,喷枪是获得优良喷涂涂层的必要保证;然而,超音速火焰喷涂枪中的冲蚀磨损不仅会对喷枪自身造成严重磨损,而且还会影响喷涂涂层的性能质量,从而导致材料的损耗和浪费。介绍了冲蚀磨损分类及其理论模型,对超音速火焰喷涂进行了介绍。总结了超音速火焰喷涂枪内表面的冲蚀磨损以及冲蚀磨损的影响因素,最后归纳了目前控制超音速火焰喷涂枪冲蚀磨损的有效措施,可为以后进行这方面的研究提供参考。     

汽轮机动叶片水蚀防护技术研究及应用

采用超音速火焰喷涂(HVOF)、超音速电弧喷涂(SWAS)制备两种抗水蚀涂层,对比分析了两种NiCr金属陶瓷涂层的组织结构、力学性能、热震性能、磨粒磨损及冲蚀磨损性能.结果表明,超音速火焰喷涂制备的NiCr金属陶瓷涂层结合强度为70 MPa,孔隙率为0.5％,涂层致密,抗热疲劳性能良好,耐磨粒磨损性能以及抗冲蚀性能优异,与2Cr13基体材料相比其抗磨损和冲蚀性能均得到显著提高.     

热循环对锅炉管热喷涂Ni-Cr基纳米涂层的影响（英文）

采用机械球磨法制备Ni-Cr基纳米原料粉末。粉末颗粒在行星球磨机中反复经历焊合、碎裂和重焊合过程。采用超音速火焰喷涂工艺(HVOF)在碳钢管上喷涂球磨纳米粉末。利用金相显微镜、XRD、扫描电子显微镜(SEM),高分辨透射电子显微镜(HR-TEM)、能谱(EDS)和显微硬度测试对原料粉和HVOF喷涂涂层进行表征。对喷涂和未喷涂试样进行热循环分析,研究相、冶金性能和显微硬度的变化。与传统喷涂试样相比,Ni-Cr纳米涂层试样具有更高的力学和冶金性能。与传统涂层相比,纳米涂层的显微组织更均匀和紧密。     

Effect of Operating Parameters on a Dual-Stage High Velocity Oxygen Fuel Thermal Spray System

High velocity oxygen fuel (HVOF) thermal spray systems are being used to apply coatings to prevent surface degradation. The coatings of temperature sensitive materials such as titanium and copper, which have very low melting points, cannot be applied using a single-stage HVOF system. Therefore, a dual-stage HVOF system has been introduced and modeled computationally. The dual-spray system provides an easy control of particle oxidation by introducing a mixing chamber. In addition to the materials being sprayed, the thermal spray coating quality depends to a large extent on flow behavior of reacting gases and the particle dynamics. The present study investigates the influence of various operating parameters on the performance of a dual-stage thermal spray gun. The objective is to develop a predictive understanding of various parameters. The gas flow field and the free jet are modeled by considering the conservation of mass, momentum, and energy with the turbulence and the equilibrium combustion sub models. The particle phase is decoupled from the gas phase due to very low particle volume fractions. The results demonstrate the advantage of a dual-stage system over a single-stage system especially for the deposition of temperature sensitive materials.     

Particle In-Flight and Coating Properties of Fe-Based Feedstock Materials Sprayed with Modern Thermal Spray Systems

New developments in the field of thermal spraying systems (increased particle velocities, enhanced process stability) are leading to improved coatings. Innovations in the field of feedstock materials are supporting this trend. The combination of both has led to a renaissance of Fe-based feedstocks. Using modern APS or HVOF systems, it is now possible to compete with classical materials for wear and corrosion applications like Ni-basis or metal-matrix composites. This study intends to give an analysis of the in-flight particle and spray jet properties achievable with two different modern thermal spraying systems using Fe-based powders. The velocity fields are measured with the Laser Doppler Anemometry. Resulting coatings are analyzed and a correlation with the particle in-flight properties is given. The experiments are accompanied by computational fluid dynamics simulations of spray jet and particle velocities, leading to a comprehensive analysis of the achievable particle properties with state-of-the-art HVOF and APS systems.     

Improved Protection Properties by Using Nanostructured Ceramic Powders for HVOF Coatings

The potential of the high-velocity oxy-fuel (HVOF) thermal spray process for reduced porosity in coatings compared to those produced by other ambient thermal spray processes is well known. The ability to produce high-density ceramic coatings offers potential in high-performance applications in the field of wear, corrosion resistance, and dielectric coatings. However, due to operational limit of the HVOF process to effectively melt the ceramic particles, the process—structure relationship must be well optimized. It has been also demonstrated that benefits from HVOF ceramic coatings can be obtained only if particles are melted enough and good lamella adhesion is produced. One strategy to improve melting of ceramic particles in relative low-flame temperatures of HVOF process is to modify particle crystal structure and composition. In this paper the effect of the powder manufacturing method and the composition on deposition efficiency of spray process as well as on the mechanical properties of the HVOF sprayed are studied. Effect of fuel gas, hydrogen vs. propane, was also demonstrated. Studied materials were alumina-, chromia-, and titania-based agglomerated powders. Coating properties such as microstructure, hardness, abrasive wear resistance, and relative fracture toughness were compared to the coating manufactured by using conventional fused and crushed powders. It can be concluded that powder size distribution and microstructure should be optimized to fulfill process requirements very carefully to produce coatings with high deposition efficiency, dense structure, improved fracture toughness, and adhesion.     

Examination of the wear properties of HVOF sprayed nanostructured and conventional WC-Co cermets with different binder phase contents

There has been an increase in interest of late regarding the properties of thermally sprayed WC-Co cermets with nanograin carbide particles. These powders have shown interesting properties in sintered components, giving high values of hardness (2200–2300 VHN) and improved wear properties. The method used for the processing for these materials—solution formation, spray drying and chemical conversion, rather than introduction of WC as solid particles to a molten binder—allows the formation of sub-100 nm WC particles as a hard second phase. The work presented here examined the effect of composition on the microstructure and wear properties of some nanostructured WC-Co materials. WC-Co cermets with 8, 10, 12, and 15% Co binder phase were deposited using a Sulzer Metco hybrid DJ HVOF thermal spray system. Optimization of deposition conditions was necessary because of the unique morphology of the powders (thick-shelled hollow spheres) to produce dense consolidated deposits. There is a higher degree of decarburization of the WC phase in the nanostructured materials compared with the conventional WC-Co. This dissolution of the hard phase is also noted to increase on decreasing binder phase content. The nanostructured WC-Co coatings have a lower wear resistance compared with the conventional WC-Co for abrasive wear and small particle erosion. The abrasive wear resistance of these nanostructured materials was found to increase on decreasing cobalt binder content. This trend in abrasive wear resistance is consistent with studies on conventional sized cermets and is believed to be more dependent upon proportion of binder phase content than degree of decarburization for the materials studied. The small particle erosion resistance of the nanostructured coatings was found to increase on increasing cobalt content.     

Sliding and Rolling Wear Behavior of HVOF-Sprayed Coatings Derived from Conventional, Fine and Nanostructured WC-12Co Powders

Fine structured and nanostructured materials represent a promising class of feedstock for future applications, which has also attracted increasing interest in the thermal spray technology. Within the field of wear protection, the application of fine structured or nanostructured WC-Co powders in the High Velocity Oxy-Fuel flame spraying technique (HVOF) provides novel possibilities for the manufacturing of cermet coatings with improved mechanical and tribological characteristics. In this study the tribological behavior of HVOF sprayed coatings derived from conventional, fine and nanostructured WC-12Co powders under sliding and rolling wear are investigated and the results are compared to C45 steel (Mat.-No. 1.0503). In addition, sliding and rolling wear effects on a microscopic level are scrutinized. It has been shown that under optimized spray conditions the corresponding fine and nanostructured WC-12Co coatings are able to obtain higher wear resistances and lower friction coefficients than the conventional coatings. This can be attributed to several scaling effects of the microstructure and to the phase evolution of the coating, which are discussed.     

Biocompatible nanostructured high-velocity oxyfuel sprayed titania coating: Deposition, characterization, and mechanical properties

Nanostructured titania (TiO₂) coatings were produced by high-velocity oxyfuel (HVOF) spraying. They were engineered as a possible candidate to replace hydroxyapatite (HA) coatings produced by thermal spray on implants. The HVOF sprayed nanostructured titania coatings exhibited mechanical properties, such as hardness and bond strength, much superior to those of HA thermal spray coatings. In addition to these characteristics, the surface of the nanostructured coatings exhibited regions with nanotextured features originating from the semimolten nanostructured feedstock particles. It is hypothesized that these regions may enhance osteoblast adhesion on the coating by creating a better interaction with adhesion proteins, such as fibronectin, which exhibit dimensions in the order of nanometers. Preliminary osteoblast cell culture demonstrated that this type of HVOF sprayed nanostructured titania coating supported osteoblast cell growth and did not negatively affect cell viability. 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.     

Residual stresses in high-velocity oxy-fuel thermally sprayed coatings – Modelling the effect of particle velocity and temperature during the spraying process

The application of thick thermally sprayed coatings on metallic parts has been widely accepted as a solution to improve their corrosion and wear resistance. Key attributes of these coatings, such as adherence to the substrate, are strongly influenced by the residual stresses generated during the coating deposition process. In high-velocity oxy-fuel (HVOF) thermal spraying, due to the relatively low temperature of the particle, significant peening stresses are generated during the impact of molten and semi-molten particles on the substrate. Whilst models exist for residual stress generation in plasma-based thermal spray processes, finite element (FE) prediction of residual stress generation for the HVOF process has not been possible due to the increased complexities associated with modelling the particle impact. A hybrid non-linear explicit–implicit FE methodology is developed here to study the thermomechanical processes associated with particle impingement and layer deposition. Attention is focused on the prediction of residual stresses for an SS 316 HVOF sprayed coating on an SS 316 substrate.     

Oxidation of stainless steel in the high velocity oxy-fuel process

The high velocity oxy-fuel (HVOF) spray process has been primarily used for the application of wear-resistant coatings and, with the introduction of new, more powerful systems, is being increasingly considered for producing corrosion-resistant coatings. In this study, the influence of various spray parameters for the JP-5000 and Diamond Jet (DJ) Hybrid systems on the oxidation of stainless steel 316L is characterized. Experimental results reveal that coating oxygen contents of less than 1 wt.% can be more easily attained with the JP-5000 than the DJ Hybrid systems because of the former’s design. In both cases, however, the low particle temperatures necessary for low oxygen content coatings may impair bond and cohesive strength. Heat treating the coatings after processing reduces hardness, metallurgically enhances bond strength, and enables the spheroidization of oxide layers surrounding unmelted particles. An empirical model describing oxidation in the thermal spray process was expanded to explain the oxidation in the HVOF spraying of stainless steel. It was concluded that for these oxygen-sensitive materials, maintaining a relatively low particle temperature throughout the spray process minimizes oxygen pickup by preventing an autocatalytic oxidation process and particle fragmentation upon impact. For the DJ Hybrid systems, understoichiometric fuel settings are selected, whereas for the JP-5000, oxygen-rich mixtures are preferred.     

New attachment for controlling gas flow in the HVOF process

During the decade, the high-velocity oxyfuel (HVOF) process proved to be a technological alternative to the many conventional thermal spray processes. It would be very advantageous to design a nozzle that provides improved performance in the areas of deposition efficiency, particle in-flight oxidation, and flexibility to allow deposition of ceramic coatings. Based on a numerical analysis, a new attachment to a standard HVOF torch was modeled, designed, tested, and used to produce thermal spray coatings according to the industrial needs mentioned above. Performance of the attachment was investigated by spraying several coating materials including metal and ceramic powders. Particle conditions and spatial distribution, as well as gas phase composition, corresponding to the new attachment and the standard HVOF gun, were compared. The attachment provides better particle spatial distribution, combined with higher particle velocity and temperature. The original version of this article was published as part of the ASM Proceedings, Thermal Spray 2003: Advancing the Science and Applying the Technology, International Thermal Spray Conference (Orlando, FL), 5–8 May, 2003, Basil R. Marple and Christian Moreau, Ed., ASM International, 2003.     

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.