激光熔覆制备高熵合金涂层的研究进展

激光熔覆技术具有高的冷却速度、低的稀释率、涂层与基体冶金结合等优点,采用激光熔覆技术制备耐磨性和耐腐蚀好的高熵合金涂层是近几年高熵合金领域的研究热点之一。首先概括了激光熔覆技术制备的高熵合金体系及组织结构特征,大多高熵合金涂层以固溶相为主,少数合金涂层形成了非晶相,与熔炼制备高熵合金块体材料相比,涂层组织具有均匀、细小致密等特点。然后介绍了涂层的性能特征,涂层具有较高的硬度、良好的耐磨性,同时指明高耐磨性涂层不仅具有高的硬度,同时还需要具有一定的塑韧性。涂层合金中大多包含有Al、Cr、Si和Co等形成稳定氧化膜的元素,呈现优异的抗腐蚀性能。随后重点概述了合金元素（Al、Mo、V、Ti、B、Ni、Nb和Cu等）、熔覆工艺参数（激光功率、扫描速度和预制层粉末厚度）和热处理工艺对涂层组织结构和性能的影响规律。其中,熔覆工艺参数对涂层组织结构和性能的影响研究相对较少,将是未来研究的重点内容之一。最后对激光熔覆技术制备高熵合金涂层存在的问题和未来的研究方向做了展望。     

NiCrSiB Coatings Deposited by Plasma Transferred Arc on Different Steel Substrates

Colmonoy 6 (NiCrSiB) is a Ni-based alloy recognized for its superior mechanical properties, attributed to the presence of a dispersion of hard carbides and borides, which is strongly dependent on processing technique. This work gathered microstructure data from the literature and analyzed Colmonoy 6 coatings deposited by plasma transferred arc hardfacing. The aim of the study was to determine the influence of PTA deposition parameters and substrate chemical composition on NiCrSiB coating characteristics. Coatings were characterized in terms of their hardness, dilution, and microstructure, as well as mass loss during abrasive sliding wear tests. The results showed that coating performance is strongly dependent on the chemical composition of the substrate. Carbon steel substrate yielded coatings with greater wear resistance. Processing parameters also alter the performance of coatings, and the lower current and lower travel speed result in reduced mass loss.     

激光熔覆铁基合金涂层的研究进展

激光熔覆技术作为一种先进的材料表面改性技术,具有加工效率高、涂层稀释率低且与基体结合强度高、自动化程度高、环境友好等优点。在各类熔覆材料中,铁基合金在成分上与钢铁材料最为接近,且其成本相对较低,近年来在设备零部件表面强化和再制造领域得到广泛应用。结合国内外最新相关研究成果,从材料体系、工艺参数、外场辅助技术等方面对激光熔覆铁基合金涂层的研究进展进行了综述。总结了熔覆材料的选材依据以及铁基自熔性合金粉末、不锈钢粉末、铁基非晶合金粉末、铁基复合粉末等各类材料的特点和应用。系统讨论了激光功率、扫描速度、光斑直径、送粉速率等工艺参数对铁基涂层成形质量和微观组织及性能的影响机制,并介绍了工艺参数优化在高质量熔覆层制备中的应用。同时,论述了超声振动、电磁场、温度场等外场辅助技术在激光熔覆铁基合金涂层中的应用,阐明了外加能场对激光熔覆过程中熔池及凝固组织的作用机理。最后对激光熔覆铁基合金涂层未来的发展方向进行了展望。     

Effect of initial deposition behavior on properties of electroless Ni–P coating on ZK60 and ME20 magnesium alloys

The composition of magnesium alloys is greatly associated with initial deposition behavior of electroless Ni–P coatings. Thus, the initial deposition behavior of electroless Ni–P coatings on ZK60 and ME20 alloys was investigated. The results indicated that differences in the alloy compositions significantly influenced the initial deposition process and the adhesive strength, corrosion resistance, and crystal structure. The initial deposition of coatings on ZK60 and ME20 alloys preferentially occurred on the precipitates. The precipitates in ZK60 alloy had higher chemical activity after HF activation and controlled the initial deposition rate of the coating. The initial deposition rate of the coating on ME20 alloy mainly depended on the density of the MgF₂ film formed by HF activation rather than on the precipitates. Owing to differences in the initial deposition process, the coating on ZK60 alloy had higher adhesive strength and better corrosion resistance than that on ME20 alloy. The coatings on ZK60 and ME20 alloys mainly had crystalline structures, and the coating on ME20 alloy had also a slight microcrystalline structure.     

Characteristics of Tribaloy T-800 and T-900 coatings on steel substrates by laser cladding

CoMoCrSi alloys, mostly known as Tribaloy® family, combine well-known outstanding properties in terms of wear and corrosion resistance as well as in terms of mechanical strength. Compared to other wear resistant alloys, their performance is due to the presence of hard Laves phases rather than intermetallic carbides. Among the Tribaloy family, the T-800 alloy offers the best performance as a result of a higher amount of primary Laves phases. However, as a consequence of the brittle nature of these hard phases, the deposited alloy may present a relatively low resistance to crack initiation and propagation, particularly in laser cladding processing where thermal stresses are significant. A reduction in the volume fraction of these hard phase may be achieved by replacing some of the Laves phase components in the alloy (Co, Mo, Si) by Ni (T-900 alloy). Alternatively, it has been suggested that the addition of Fe could also lead to a significant reduction. The Fe addition can easily be accomplished in laser cladding process by dilution of the T-800 coating with the steel substrate. In this work a comparative study of microstructure, hardness and cracking susceptibility of low and high diluted T-800 and T900 coatings deposited by laser cladding is presented. A lower cracking ratio is obtained for the T-900 coatings at the cost of a lower hardness and wear resistance. No noticeable effect on the cracking susceptibility of the T-800 is found due to dilution with the substrate. However a change in its microstructure is observed giving superior hardness and wear resistance.     

Al-Si-Mn Alloy Coating on Aluminum Substrate Using Cold Metal Transfer (CMT) Welding Technique

The cold metal transfer (CMT) process was explored as a weld overlay technique for synthesizing Al-Si-Mn alloy coating on a commercially pure Al plate. The effect of welding speed on the bead geometry, deposition rate, and the dilution were studied and the best parameter was used to synthesize the coatings. The CMT process can be used to produce thick coatings (>2.5 mm) without porosity and with low dilution levels. The Vickers hardness number of the Al substrate increased from 28 in the bulk to 57 in the coating. It is suggested that the CMT process can be an effective and energy-efficient technique for depositing thick coatings and is useful in weld repair of aluminum alloy components.     

Effect of arc current on microstructure and wear characteristics of a Ni-based coating deposited by PTA on gray cast iron

The plasma transferred arc (PTA) technique is currently used to coat the edges of moulds for the glass industry with nickel-based hardfacing alloys. However the hardness and wear performance of these coatings are significantly affected by the procedure adopted during the deposition of coatings. The aim of the present investigation is to study the effect of arc current on the microstructure, hardness and wear performance of a nickel-based hardfacing alloy deposited on gray cast iron, currently used in molds for the glass industry. Microstructure, hardness and wear assessments were used to characterize the coatings. Electron probe micro analysis (EPMA) mapping, scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDAX) and X-ray diffraction (XRD) were used to characterize the microstructure of the deposits. The effect of post weld heat treatment (PWHT) on the microstructure and hardness was also studied. The typical microstructure of the coatings consists of dendrites of Ni-Fe, in the FCC solid solution phase, with interdendritic phases rich in Cr-B, Ni-Si and Fe-Mo-C. Increasing the arc current reduces the proportion of porosity and hardness of the coatings and modifies their composition due to the increasing dilution of the cast iron. The partial melted zone (PMZ) had a typical white cast iron plus martensite microstructure, while the heat affected zone (HAZ) had only a martensite structure. The wear tests showed decreasing wear resistance with decreasing hardness of the coatings. PWHT reduces the hardness of the PMZ and HAZ but does not significantly alter the hardness of the bulk coating.     

Effects of TaN nanoparticles on microstructure,mechanical properties and tribological performance of PEEK coating prepared by electrophoretic deposition

In order to solve the friction, wear and lubrication problems of titanium, a series of TaN/ployether- ether-ketone (PEEK) coatings were developed by electrophoretic deposition, and the effects of TaN nanoparticles on the microstructure, mechanical properties and tribological performance of coatings were explored. Results manifest that the introduction of TaN nanoparticles into PEEK coatings could improve the deposition efficiency, enhance the resistant deform capacity, increase the hardness, elastic modulus and adhesive bonding strength. Compared with the pure PEEK coating, the friction coefficient of P-TN-3 was greatly reduced by 31.25%. The wear resistance of P-TN-3 was also improved in huge boost, and its specific wear rate was decreased from 9.42×10^-5 to 1.62×10^-5 mm³·N^-1·m^-1. The homogeneous composite TaN/PEEK coatings prepared by electrophoretic deposition were well-adhered to the titanium alloy substrate, TaN nanoparticles could improve the strength of PEEK coating, and provide wear-resistance protection for titanium alloys.     

Microstructure Characteristics and Mechanical Properties of Al-12Si Coatings on AZ31 Magnesium Alloy Produced by Cold Spray Technique

The cold spray technique was to deposit Al-12Si coatings on AZ31 magnesium alloy. The influence of gas pressure and gas temperature on the microstructure of coatings was investigated so as to optimize the process parameters. OM, SEM, and XRD were used to characterize the as-sprayed coatings. Mechanical properties including Vickers microhardness and adhesion strength were measured in order to evaluate coating quality. Test results indicate that the Al-12Si coatings possess the same crystal structure with powders, sufficient thickness, low porosity, high hardness, and excellent adhesion strength under optimal cold spray process parameters.     

喷射成形与铸造7A60合金的微观组织对比研究

利用喷射成形技术制备了7A60合金。借助扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD）等手段研究了喷射成形与铸造7A60合金微观组织的特点。结果表明，铸造7A60合金的组织粗大，偏析严重。喷射成形7A60合金主要由细化的等轴晶组成，无明显偏析。与传统铸锭冶金工艺相比，喷射成形工艺大大提高了冷却速率，显著细化了7A60合金的微观组织。     

镁合金表面冷喷涂层防护研究进展

镁合金作为最轻质的金属结构材料,由于其密度低和比强度高等优良的物理和力学性能,在航空、航天、汽车以及电子等领域引起广泛关注。然而,镁合金化学性质活泼、耐腐蚀和耐磨损性差等缺点严重制约其进一步应用。近些年发展起来的冷喷涂技术,在固态下制备涂层,涂层致密且与基体结合良好,因此可为镁合金表面防护提供一种新的有效方法。主要综述了镁合金表面冷喷涂耐腐蚀涂层(纯铝、铝合金和复合材料涂层)和耐磨损涂层(合金和复合材料涂层),论述了影响冷喷涂层耐腐蚀、耐磨损以及其他力学性能(硬度和涂层/基体结合强度)的主要因素,包括杂质元素含量、合金种类以及复合材料涂层中陶瓷颗粒含量、尺寸和形貌等。对比了几种常用表面处理技术制备的纯铝涂层的耐腐蚀性能,并阐述了冷喷涂技术在镁合金表面防护方面的优势。此外,还分析了热处理对冷喷涂纯铝和复合材料涂层耐蚀性的影响。最后提出了目前冷喷涂技术在镁合金防护方面的局限性以及发展难题,对未来研究趋势进行了展望。     

Electrochemical Deposition of Ni on an Al-Cu Alloy

Metallic coatings can be used to improve the wear and corrosion resistance of Al alloys. In this study, Ni was used as a candidate material for such a coating which was applied on the surface of Al 2014 alloy using electrodeposition in a standard Watt’s bath. A two-step heat treatment procedure was employed that served to increase the adhesion as well as hardness of Ni. Deposition was undertaken for different durations using both galvanostatic and potentiostatic techniques. The effect of deposition parameters such as surface finish, current, potential, temperature, pH level and duration on the microstructure, adhesion, and surface properties of the Ni deposit was studied. Materials characterization was performed using scanning electron microscopy, atomic force microscopy, and x-ray diffraction. Cross-sectional scanning transmission electron microscope images revealed the fine-grained (10 nm) structure of Ni initially deposited at the Ni-Al alloy substrate. Microhardness, adhesion, and corrosion behavior of the Ni deposit were evaluated. Experimental results indicate that deposition by galvanostatic technique on 1 μm surface finish at 45 °C with a pH level maintained at 3.6 represented the optimum conditions to generate a uniform Ni deposit on Al 2014. It was concluded that Ni deposition can be used to improve the surface properties of Al alloys.     

AISI1045钢表面激光熔覆FeCoCrNiAl0.5Ti0.5涂层的界面特性及摩擦性能

激光熔覆高熵合金涂层摩擦磨损行为的研究主要聚焦在涂层表面,鲜有对熔覆层/基体界面区域的摩擦学行为进行研究。为了提高AISI 1045钢的耐磨性,采用激光熔覆技术在AISI 1045钢基体表面制备宏观形貌良好、组织均匀的FeCoCrNiAl_0.5Ti_0.5高熵合金涂层。利用OM、XRD、SEM、EDS和摩擦磨损测试仪对激光熔覆FeCoCrNiAl_0.5Ti_0.5涂层的微观结构、物相组成、界面特性和摩擦磨损性能进行研究。通过对FeCoCrNiAl_0.5Ti_0.5涂层XRD图谱和元素分布分析发现,涂层主要由面心立方(Fe,Ni)相和体心立方相(BCC)形成的共晶组织及其中弥散分布着的Ni Al金属间化合物构成。硬度测试表明,从涂层顶部到基体,涂层、稀释区、热影响区和基体的平均显微硬度分别为518±20、561±63、473±81和217±12 HV0.2。涂层/基体界面区域生成了Cr₂₃C₆,在摩擦过程中会形成一层摩擦...     

钛合金表面激光熔化沉积钛基复合材料涂层的组织及性能

通过激光熔化沉积TA15+30%TiC(体积分数)混合粉末,在TA15钛合金表面制备出钛基复合材料涂层,分析了涂层的组织、硬度及界面结合强度。结果表明,激光熔化沉积过程中原始TiC颗粒发生溶解,并在凝固过程中重新析出细小的TiC,TiC有等轴状及枝晶两种形态,涂层中存在部分未熔的TiC颗粒;涂层硬度达HRC 60;涂层与基体界面为完全冶金结合,涂层的界面结合强度大于310 MPa,抗剪切强度为330 MPa;经弯曲及热震试验后,涂层未出现剥落现象,表明涂层与基体具有很好的相容性     

Solidification microstructures of Al-Zn-Mg-Cu alloys prepared by spray deposition and conventional casting methods

High strength Al-Zn-Mg-Cu alloys were prepared by spray deposition and casting techniques. The microstructures of the Al-Zn-Mg-Cu alloys were studied using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Secondary phases in the microstructures of the alloys prepared by spray deposition and conventional cast were examined. The results indicate that under the conventional casting condition, the microstructure of the alloy revealed the presence of coarse Al/Mg（ZnCu）2 eutectic phases, and the spray deposited process causes an obvious modification in size, morphology, and distribution of secondary phases in the microstructure as well as reduction of segregation. The superior microstructure of the spray-deposited Al-Zn-Mg-Cu alloy was attributed to the high cooling rate, and associated with the rapid solidification process.     

Effect of TiN/Ti composite coating and shot peening on fretting fatigue behavior of TC17 alloy at 350 °C

A TiN/Ti composite coating has been prepared on a TC17 titanium alloy substrate by an ion-assisted arc deposition (IAAD) technique with a view to improving the fretting fatigue resistance of the titanium alloy at 350 °C. The composition distribution, bonding strength, micro-hardness, ductility, tribological properties, and fretting fatigue resistance at elevated temperature of the coating have been investigated. The results indicate that the IAAD technique can be used to prepare a TiN/Ti composite coating with high hardness, good ductility, excellent bonding strength, and high load-bearing capability. The TiN/Ti composite coatings can improve the resistance to wear and fretting fatigue of the Ti alloy, as manifested in its excellent tribological behavior at 350 °C. However, the fretting fatigue resistance of the titanium alloy treated by shot peening (SP) combined with IAAD TiN/Ti coating post-treatment was lower than that by IAAD TiN/Ti coating or SP alone, because the compressive residual stress induced by SP was significantly relaxed during coating process and the coating easily cracked and broke off.     

钛合金表面激光熔覆陶瓷涂层的研究进展

针对钛合金在实际应用过程中存在硬度低、耐磨性差、高温易氧化以及生物活性低等问题,国内外学者利用陶瓷材料较高的硬度、优异的耐磨性和高温抗氧化性能的特点,以及激光熔覆技术可以实现涂层与基材的冶金结合,较高的冷却速率使涂层内部晶粒得到细化的优势,开展了钛合金表面激光熔覆陶瓷涂层的广泛研究。首先简要概括了钛合金表面激光熔覆陶瓷材料的特点,介绍了在激光熔覆过程中常见的陶瓷材料以及所具备的特殊性能。从陶瓷涂层制备方式和陶瓷材料体现的功能两个方面,综述了国内外的研究特点、现状和进展。对比分析了激光制备纯陶瓷涂层、激光制备陶瓷与金属合金复合涂层、激光原位合成陶瓷复合涂层、激光制备陶瓷梯度涂层的优缺点。介绍了在钛合金表面激光熔覆耐磨涂层、高温抗氧化涂层、耐蚀涂层和生物涂层的进展,分析了陶瓷材料在提高相关性能时所发挥的作用。最后针对钛合金表面激光熔覆陶瓷材料存在的问题,对钛合金表面激光熔覆陶瓷涂层未来的发展趋势进行了讨论与展望。     

沉积温度对高性能TiAlN涂层微观结构和力学性能的影响

采用真空电弧离子镀（AIP）技术在不同沉积温度下TiAlN涂层,用于高性能制造,并研究了沉积温度与表面性能的关系。结果表明,由于离子轰击作用,表面大颗粒随沉积温度的升高而减少。随着沉积温度的升高,涂层表面的晶粒尺寸先急剧减小后逐渐增大。此外,沉积温度对合成涂层的相组成和化学成分影响不大。随着沉积温度的升高,硬度和粘结强度先迅速增加,后逐渐降低。当沉积温度在450℃左右时,沉积的TiAlN涂层硬度最高,粘结强度最大。上述现象的发生机理与沉积过程中表面与界面之间的微观组织和残余应力的变化有关。合成的涂层在高达900℃的空气中具有良好的热稳定性。     

Duplex surface layer treatment of Al alloy: electron beam alloying and plasma nitriding

Abstract

Al alloys offer a high potential as lightweight construction materials due to their low density, specific strength and processing properties. However, the field of application is limited by their low hardness and poor wear properties. Duplex surface treatment combining electron beam (EB) alloying and plasma nitriding offers one possibility to produce hard and wear resistant surface layers on Al alloys. The EB alloyed surface layer acts as supporting layer for the hard AlN coating so that the load bearing capacity can be enhanced. In the present study duplex treatment of Al-5083 (AlMg4·5Mn0·7) Al alloy has been investigated. Before the EB treatment alloying material deposition was carried out by atmospherically plasma spraying. Various sandwich layers based on Al and Fe respectively, have been applied. Different beam deflection techniques have been tested and their effect on surface deformation, microstructure and hardness was evaluated. Plasma nitriding was carried out in order to evaluate the nitriding behaviour of the surfaces modified by EB. Applying the EB meander technique results in smooth surfaces, good microstructural connection to the matrix material and a homogeneous distribution of the alloying elements together with an increase in hardness of ～300 HV0·1. Plasma nitriding leads to the formation of AlN layers of ～5 μm thickness.     

Laser surface modification using Inconel 617 machining swarf as coating material

A single-stage, blown powder laser cladding process is used to deposit a protective layer of Ni-based alloy Inconel 617 on mild steel substrates. A Design of Experiments methodology is used to analyse the effects of the major laser cladding processing parameters on the deposited layer characteristics. Layer thickness, microstructure, dilution, elemental composition and corrosion resistance are analysed and correlated with the processing parameters and the overall effectiveness of the protective coating assessed. The work is different in that the protective material, usually in the form of costly powder, is in this case virtually cost-free and simply recycled from machining waste without any costly atomisation or similar process. The results show a number of significant relationships between the processing parameters and the effectiveness of the protective coating. The layer thickness and hardness were found to increase with the mass feed rate and decrease with an increase in laser power. A mainly columnar dendritic microstructure was observed in the clads. There was no evidence of significant bonding defects, trapped unmelted particles or porosity under most conditions. In all samples, the coatings displayed significant higher corrosion resistance than the mild steel sample.