等离子熔覆镍包WC/Fe-Cr-B-Si复合涂层微观组织

采用等离子熔覆技术在Q235钢表面制备了镍包WC含量(质量分数)分别为10%、30%、50%的WC/Fe-Cr-B-Si复合涂层。采用OM、SEM、EDS、XRD等手段研究了涂层的组织,利用显微硬度计测试了涂层的显微硬度。结果表明,添加10%镍包WC的涂层中WC几乎全部溶解,而在含30%、50%镍包WC涂层中均存在未溶解的WC,且在复合涂层微观组织演变中发现了明显不同的凝固特征,含10%、30%镍包WC的涂层主要是枝晶和枝晶间共晶的亚共晶组织;而在含50%镍包WC的涂层中是以初晶Fe3W3C为主和过共晶组织。添加10%、30%、50%镍包WC的复合涂层显微硬度分别为560~600、650~800、920~1100 HV0.2,硬度随WC含量的增加而提高。     

铝合金表面MoSi2／SiC复合涂层的激光熔覆制备

利用激光熔覆技术在铝合金表面制备MoSi2／SiCp复合涂层，对涂层的微观组织形成规律及其主要工艺参数对涂层组织和性能的影响进行了研究。实验结果表明，对试样进行搭接预热和在熔覆粉末中添加助熔剂CaF2是提高熔覆层质量的主要途径。采用多道搭接预热熔覆工艺和预置涂层法可以在铝合金表面获得具有完全冶金结合的原位自生SiC颗粒增韧的硅化钼陶瓷复合涂层，涂层组织主要由Mo（Si，Al）2、SiC、α-Al、Mo5Si3等相组成。熔覆层显微硬度较基体材料的显微硬度有大幅度提高，涂层显微硬度最大可达850HV0.2.     

Vacuum brazing of Si/SiC ceramic composite and Invar alloy using Ti50Cu-W filler metals

Si/ SiC ceramic composite and Invar alloy were successfully joined by vacuum brazing using Ti50Cu-W filler metals into which W was added to release the thermal stress of the brazed joint.Microstructure...     

激光熔覆SiC/Co复合涂层的组织与性能研究

在45钢表面采用激光熔覆工艺制备了SiC/Co复合涂层,分析了涂层的显微组织,测试了涂层的硬度和摩擦学性能.结果表明:SiC/Co涂层主要由γ-Co和Cr<,23>C<,6>共晶组织组成,涂层结合区为枝晶,熔覆区为等轴晶;熔覆区的显微硬度为1300～1500HK,约为45钢基体硬度的4倍;该涂层明显改善了45钢基体的摩...     

Microstructure and wear properties of TiC/FeCrBSi surface composite coating prepared by laser cladding

Titanium carbide particles reinforced Fe-based surface composite coatings were fabricated by laser cladding using a 5 kW CO₂ laser. The microstructure, phase structure and wear properties were investigated by means of scanning electron microscopy, transmission electron microscopy and X-ray diffraction, as well as dry sliding wear test. The results showed that TiC carbides were formed via in situ reaction between ferrotitanium and graphite in the molten pool during the laser-clad process. The morphology of TiC is mainly cubic and dendritic form; and the TiC carbides were distributed uniformly in the composite coating. The TiC/matrix interface was found to be free from cracks and deleterious phases. The coatings reinforced by TiC particles revealed higher wear resistance and lower friction coefficient than that of the substrate and FeCrBSi laser-clad coating.     

Influence of powder particle injection velocity on the microstructure of Al-12Si/SiCp coatings produced by laser cladding

The influence of powder particle injection velocity on the microstructure of coatings consisting of an Al-Si matrix reinforced with SiC particles prepared by laser cladding from mixtures of powders of Al-12 wt.% Si alloy and SiC was investigated both experimentally and by modeling. At low injection velocities SiC particles react with the molten aluminum alloy. Only a small fraction of SiC remains in the microstructure, which contains large amounts of particles of the reaction products Al₄SiC₄ and Si dispersed in the α-Al + Si eutectic matrix. By contrast, at high injection velocities chemical reactions between SiC and molten aluminum are almost entirely suppressed and the resulting microstructure consists only of SiC particles dispersed in the matrix. To investigate whether this behavior could be explained by the different temperatures reached by the injected particles as they fly through the laser beam, a physical-mathematical model describing the interaction between the laser beam and the powder stream in the off-axis blown powder laser cladding process was developed and applied to calculate the temperature attained by the powder particles as a result of their interaction with an Nd:YAG laser beam (λ = 1.06 µm). At an injection velocity of 1 m/s the maximum temperature attained by SiC and Al-12Si particles is 3150 and 180 ºC, respectively. This result demonstrates that particle injection velocity is a major parameter affecting the microstructure of coatings produced by laser cladding, and must be carefully controlled.     

SiC颗粒增强铁基合金复合涂层的组织

采用等离子堆焊—SiC后送粉技术制备了SiC颗粒增强铁基合金复合涂层,利用扫描电子显微镜（SEM）、X射线衍射仪（XRD）和能谱仪（EDS）对涂层的显微组织、相组成和元素分布进行了观察和测试。试验结果表明：SiC分布于马氏体基体上,原始形态保持完好,没有发生明显溶解,复合效果较好。SiC与基体界面层由预覆层、近基体区和絮状区构成。SiC边缘为CrSi2、CrSi3;近基体区耐腐蚀性相对基体较强,组织难以显示;絮状区由大量（Fe,Cr）7 C3、（Fe,Cr）23 C6碳化物和α-（Fe,Cr）固溶体组成。     

激光熔覆Ni基合金/SiC涂层耐冲蚀性能的研究

采用激光熔覆技术分别在45#钢表面制备Ni基合金及Ni基合金/SiC涂层,研究了熔覆层的硬度和耐冲蚀性能,探讨了熔覆层的冲蚀磨损机理.     

Laser cladding of Ni/Cu/Al functionally graded coating on magnesium substrate

Laser cladding of graded multi-layer Ni/Cu/Al coatings on magnesium substrates was performed with the aim of improving the inherently low corrosion and wear resistance of magnesium. The quality of the coating was found to be good: the interfaces between the different layers are generally free from any major solidification defects such as porosity and cracks. Despite the fact that considerable mixing had occurred in the Al layer, the top Ni layer was free from Al and Mg. The top Ni layer comprises a single solid solution (Ni) phase; its corrosion and wear resistance was found to be excellent. The wear properties of the coating were explained in terms of stacking fault energy and the ratio of hardness to elastic modulus.     

电子封装用Al/Si/SiC复合材料的显微组织与性能(英文)

采用气压浸渗法制备中体积分数电子封装用 Al/Si/SiC 复合材料。在保证加工性能的前提下,用与 Si 颗粒相同尺寸(13 μm)的 SiC 替代相同体积分数的硅颗粒制得复合材料,并研究其显微组织与性能。结果显示,颗粒分布均匀,未发现明显的孔洞。随着 SiC 的加入,强度和热导率将得到明显提高,但热膨胀系数变化较小,对使用影响也不大。讨论几种用于预测材料热学性能的模型。新的当量有效热导被引入后,H-J 模型将适用于混杂和多颗粒尺寸分布的情况。     

Laser cladding of eutectic-based Ti-Ni-Al alloy coating on magnesium surface

A Ti_70.3Ni_22.2Al_7.5 alloy, optimized from a basic binary eutectic Ti₇₆Ni₂₄ alloyed with different amounts of Al, was laser-clad on AZ91HP magnesium alloy. The coating mainly consists of β-Ti solid solution and Ti₂Ni intermetallic compound resulting in high hardness, good wear resistance and corrosion resistance. The interface between the clad layer and the substrate has a good metallurgical bonding.     

Effect of laser irradiation on failure mechanism of TiCp reinforced titanium composite coating produced by laser cladding

Laser cladding is an effective technique to coat a metallic substrate with a layer of a different nature. It has been widely reported that the most important combined parameters controlling the quality of the coating are the specific energy (E) and the powder density (Ψ). In the present work, clad deposits of Ti6Al4V + 60 wt.% TiC were prepared on a Ti6Al4V substrate using an optimum combination of E_c = 24 J/mm² and ψ_c = 3 mg/mm². These experiments were performed using a laser power of 400 and 600 W, in order to study the effect of laser power on the properties of the clad. The microstructure, phase composition and nanohardness of the coatings were investigated by optical microscopy, scanning electron microscopy and X-ray diffraction. During laser processing, TiC can be partially converted to TiC_X (X = 0.5) due mainly to the TiC dissolution into the laser-generated melting pool and subsequent precipitation during cooling. It was observed that the lower laser power limit reduces primary TiC dissolution but it also promotes secondary carbide alignment at the interface. On the other hand, the damage mechanism induced by high laser power is dominated by primary TiC particle cracking by the high stress concentration at the particle–matrix interface followed by ductile failure of the matrix. It is also remarkable that irradiance affects the TiC/TiC_x ratio despite E_c and ψ_c are fixed and it determines hardness distribution inside the coating.     

Morphological evolution of primary TiC carbide in laser clad TiC reinforced FeAl intermetallic composite coating

1　INTRODUCTIONIronaluminumbasedonFeAlintermetallicalloywasexpectedtobeanimportantandpotentialhightemperaturematerial,becauseitsgoodresistancetooxidationandcorrosion ,lowdensityandhightem peraturemelting point[12 ] .However ,theintrinsicpropertiesofFeAlintermetallicalloy ,suchaslowductilityandlowfracturestrength ,limiteditsindus trialapplications .Howtoimprovemechanicalproper tiesofFeAlintermetallicalloyandexpanditsindus trialapplicationrealmwasanimportantresearchas pectformaterialworke…     

Study on microstructures of micron Si3N4 composite ceramic with addition of nano SiC and SiC whisker

１－ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅＳｉ３Ｎ４ｃｅｒａｍｉｃａｓａｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔｒｕｃｔｕｒａｌｍａｔｅｒｉａｌｈａｓａｔｔｒａｃｔｅｄａｎｅｘｔｅｎｓｉｖｅａｔｔｅｎｔｉｏｎｌｏｎｇａｇｏ,ａｎｄｗａｓｅｘｔｅｎｓｉｖｅｌｙｓｔｕｄｉｅｄｉｎ７０′ｓｉｎＵＳＡ,ＵＫ,ＧｅｒｍａｎｙａｎｄＪａｐａｎ,ｂｕｔｔｈｅｆｉｅｌｄｓｏｆａｐｐｌｉｃａｔｉｏｎｗｅｒｅｒｅｓｔｒｉｃｔｅｄｂｅｃａｕｓｅｉｔｓｓｔｒｅｎｇｔｈｄｒａｍａｔｉｃａｌｌｙｄｅｓｃｒｅａｓｅｓａｔａｂｏ…     

Effect of SiC particle addition on microstructure of Mg2Si/AI composite

In the present study, by adding SiC particles into Al-Si-Mg melt, Mg2Si and SiC particles hybrid reinforced Al matrix composites were fabricated through the Mg2Si in situ synthesis in melt combined with the SiC ex situ stir casting. The as-cast microstructure containing primary Mg2Si and SiC particles that distribute homogenously in Al matrix was successfully achieved. The effects of SiC particle addition on the microstructure of Mg2Si/Al composites were investigated by using scanning electron microscopy(SEM) and XRD. The results show that, with increasing the fraction of the SiC particles from 5wt.% to 10wt.%, the morphologies of the primary Mg2Si particulates in the prepared samples remain polygonal, but the size of the primary phase decreases slightly. However, when the SiC particle addition reaches 15wt.%, the morphologies of the primary Mg2Si particulates change partially from polygonal to quadrangular with a decrease in size from 50 μm to 30 μm. The size of primary Al dendrites decreases with increasing fraction of the SiC particles from 0wt.% to 15wt.%. The morphology of the eutectic Mg2Si phase changes from a fi ber-form to a short fi ber-form and/or a dot-like shape with increasing fraction of the SiC particles. Furthermore, no signifi cant change in dendrite arm spacing(DAS) was observed in the presence of SiC particles.     

激光熔覆制备颗粒增强铁基复合涂层中马氏体亚结构

通过在Fe-C-Si-B粉末体系中添加强碳化物形成元素Ti的方法,激光熔覆制备了原位合成颗粒增强铁基复合涂层.用扫描电子显微镜和透射电子显微镜对其微观组织进行了研究,重点分析了激光熔覆过程中马氏体的形成和亚结构的转变.结果表明,熔覆层无气孔和裂纹、组织均匀,是一种典型的亚共晶组织,由马氏体、莱氏体、残留奥氏体和原位生成的TiC颗粒组成.涂层中的马氏体是{211},<113>系片状孪晶马氏体,二次回火效应使得马氏体中析出了大量的具有纳米尺度的渗碳体,与马氏体具有一定的取向关系.     

激光熔覆WC-Ni基超硬梯度复合涂层的组织与性能

利用激光宽带熔覆技术在45钢表面制备了WC-Ni基超硬梯度复合涂层.对激光熔覆层用SEM、EDS、XRD进行观察和分析.对比研究了单一熔覆层、梯度熔覆层的熔覆层形貌、缺陷状态、硬度及其分布.结果表明,单一熔覆层易出现宏观裂纹、界面处熔合差等缺陷;梯度激光熔覆层逐级过渡的结合形式缓解了应力集中,使应力合理分布.在优化的工艺参数下,通过连续控制微观结构要素,可以实现成分、组织的梯度变化,获得无气孔、无裂纹的梯度熔覆涂层.其中,梯度熔覆层组织主要是由γ-Ni、WC等相组成,涂层的硬度值从熔覆层至基体呈梯度降低趋势,外层平均硬度可达2000 HV0.1以上.     

等离子熔覆高铬铁基复合涂层高温滑动磨损性能

利用前驱体碳化复合粉末制备技术,以蔗糖为碳的前驱体制备了等离子熔覆Fe-Cr-C-W-Ni复合粉末.采用等离子熔覆丁艺,用该粉末在凋质C级钢基材表面制备了高铬铁基复合涂层.测试了涂层在不同增强相含量、不同载荷和不同温度干滑动磨损条件下的耐磨性,并讨论了磨损机理.结果表明,由于涂层中硬质耐磨相(Cr,Fe)7C3的扰磨骨干作用,涂层在高温千滑动磨损条件下具有优异的耐磨性能.利用该技术在高速线材轧辊上使用效果明显.     

Sliding wear resistance of TiCp reinforced titanium composite coating produced by laser cladding

Titanium metal matrix composite coatings (MMC) are considered to be important candidates for high wear resistance applications. Laser cladding (LC) by coaxial powder feeding is an advanced coating manufacturing process, which involves laser processing fine powders into components directly from computer aided design (CAD) model.In this study, the LC process was employed to fabricate TiC particle reinforced Ti6Al4V MMC coatings on Ti6Al4V hot rolled samples.The experimental results show that during LC process, TiC particles are partially dissolved into melted Ti-base alloy and precipitated in the form of TiC dendrites during cooling.Dry sliding wear properties of these MMC layers have been compared with substrate materials wear. The observed wear mechanisms are summarized and related to detailed microstructural observations. The layers have been found to show improved tribological properties connected with the TiC_p addition and the LC process parameters.