镍基复合材料涂层的激光熔覆制备及表征

利用激光熔覆技术在在0Cr18Ni9奥氏体不锈钢表面制备了NiCr/Cr3C2-MoS2-BaF2复合材料耐磨自润滑涂层,采用X衍射仪（XRD）、扫描电子显微镜（SEM）、能谱仪（EDS）分析了熔覆层的物相组成及显微组织,采用显微硬度计测试了涂层沿层深方向的显微硬度分布,并在室温环境下对涂层进行干滑动摩擦磨损试验。结果表明：涂层主要由γ-( Ni,Fe)共晶化合物、碳化物硬质Cr7C3、CrS以及少量的MoS2润滑相和少量BaF2组成,熔覆层的显微硬度平均值约为783 HV0.2,是基体的2.44倍,熔覆层总体摩擦因数和磨损率明显低于基体,磨损率约为基体的1/5。磨损过程中产生的润滑氧化膜有利于提高其耐磨损性能。     

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.     

氩弧熔覆SiC/Ni复合材料涂层组织与抗磨性分析

以Ni60A粉、SiC粉为原料,利用氩弧熔覆技术在Q235钢基材表面制备出复合涂层,应用SEM和XRD方法分析了涂层的显微组织.结果表明,复合涂层与基材实现了良好的冶金结合,复合材料涂层无单独的SiC,而是由Ni3 Si枝晶、M7 C3和γ-Ni固溶体组成,.Ni3Si枝晶均匀的分布γ-Ni固溶体基体上,涂层的显微硬度达到1 100HV0.2,涂层的耐磨性较基体提高近13倍.     

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.     

退火处理对激光熔覆FeCoCrNiB/SiC高熵合金涂层组织与性能的影响

采用激光熔敷技术在45号钢表面制备不同SiC含量的FeCoCrNiB/SiC高熵合金涂层。研究退火温度对FeCoCrNiB/SiC涂层组织结构、硬度和耐磨性的影响。结果表明：未加SiC时,涂层由简单FCC固溶体和柳叶状Cr2B相组成。加入SiC后涂层中基体仍然为简单FCC固溶体,但基体内部出现了条状碳化物M7C3和方块状硼化物Fe2B。随着SiC添加量的增加,FeCoCrNiB/SiC涂层析出碳化物和硼化物颗粒尺寸显著变小,碳化物含量逐渐增多,涂层硬度和耐磨损性显著提高。FeCoCrNiB/SiC涂层经过高温退火后相结构较稳定,但组织有一定程度的粗化。添加10wt%SiC的涂层在900 ℃高温退火后硬度下降仅4 %,具有良好的抗高温软化特性。添加SiC颗粒改变了FeCoCrNiB涂层的磨损机制,抑制了涂层的氧化磨损。FeCoCrNiB/SiC涂层经900 ℃高温退火后仍保持良好的耐磨损性能。     

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.     

Blast and tensile properties of tantalum/niobium lined SiC/SiC composite tubes for nuclear cladding

The mechanical performances such as tensile strength and blast property of metal lined SiC/SiC composite cladding tubes were investigated. Nb or Ta was selected as liner material, and the SiC/SiC composite layer was fabricated by winding and different precursor impregnation and pyrolysis (PIP) processes. The tensile strengths of different tube samples were measured at room temperature (RT) and 1200 °C, respectively. The blast property was investigated through the maximum water pressure of tubes. And the fracture microstructures were observed by SEM. The highest tensile strength at RT was 150.7 MPa. The blast strength was enhanced with the PIP process increasing from 1 to 4 cycles and the tube of 4 PIP cycles had the highest water pressure of 34.7 MPa. Compared with the metal tubes, the multi-layer structure improved tensile and blast properties significantly. The different processes such as PIP cycles and pyrolytic carbon (PyC) coating were important factors to enhance the mechanical performances of SiC/SiC-based tubes. However, the retention rate of tensile strength was only 18.5% at 1200 °C.     

超声辅助激光熔覆SiC/316L温度场和应力场分析

建立了激光熔覆SiC/316L复合涂层有限元分析模型,采用超声振动热效应转化和施加动态边界条件相结合的方法对超声振动边界条件作近似处理,对超声辅助激光熔覆SiC/316L复合涂层的温度分布和残余应力进行分析,并分析了超声振幅和扫描速度对温度场和应力场的影响.结果表明,随着超声振幅增大和扫描速度减小,涂层表面温度升高;超声作用下涂层残余应力有所降低,且随着超声振幅和扫描速度增大,残余应力值先减小后增大.采用优化工艺参数进行超声熔覆试验,超声作用使涂层中各区域组织得到细化且均匀分布,有利于降低涂层中残余应力.     

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.     

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ZrB2-SiC增强Cu基复合涂层的微观结构与摩擦学性能

为了提高铜表面的强度和耐磨性,以复合粉末(Zr、Si、Ni包B4C、Cu)为原料,采用激光辅助原位合成技术,在纯铜基体表面制备了ZrB₂-SiC/Cu复合涂层。通过XRD、SEM和TEM分析了复合涂层的表面形貌、微观结构、相组成和界面结合,并测试了不同增强相含量熔覆层的硬度和摩擦学性能。结果表明：通过设计的原位化学反应成功在铜基体内合成了微米级针状ZrB₂和纳米级颗粒状SiC。增强相均与基体形成了清洁、无杂相的界面。2种不同维度与尺寸的增强体,通过多种强化机制,显著改善了复合涂层的力学性能;通过调整激光工艺参数可实现增强体尺寸的控制,随着增强相含量的提高,复合涂层的平均硬度和耐磨损性逐渐增加。当增强相含量为30%(质量分数,下同)时,复合涂层的平均硬度(HV0.2)为3028 MPa,约为纯铜的5.6倍。30%增强相涂层的载流磨损率与10%增强相的涂层相比,降低了约80%。较高含量增强相的复合涂层表现出优异的摩擦学性能。     

原位生成WC/TaC复合激光熔覆层组织研究

利用激光熔覆技术,将氧化钽和石墨的混合粉末添加到Ni60包WC的镍基合金粉末中,成功制备了TaC/WC复合涂层。使用扫描电镜(SEM)、X射线衍射仪(XRD)等仪器分析了镍基合金复合涂层横断面的显微组织,并对其硬度进行研究分析。结果显示在基体与涂层之间形成了良好的冶金结合,复合涂层不仅含有γ-Ni树枝晶、W₂C、M₇C₃、以及大量的弥散分布的TaC颗粒。复合涂层的硬度可达HV965,是Ni60涂层的1.3倍,主要是因为TaC颗粒的分布促使其内部组织结构改变以及相变引起的硬度上升。     

Al/Si比例对TC4合金表面激光熔覆Ti-Al-Si涂层组织与摩擦性能的影响

以不同Al/Si比例的Ti-Al-Si复合粉末为原料,采用激光熔覆技术在TC4合金表面制备Ti-Al-Si涂层,研究了Al/Si比例对涂层物相、微观组织、显微硬度及摩擦磨损性能的影响.结果表明,单道熔覆的涂层中没有发现明显的裂纹及气孔,涂层与基体之间呈现良好的冶金结合.不同Al/Si比例涂层中组织均以熔断的枝晶为主,枝...     

超声振动对激光熔覆TiC/FeAl复合涂层温度场的影响

采用超声振动热效应转化和施加动态边界条件的方法对超声振动边界条件作近似处理,研究了超声振动辅助激光熔覆TiC/FeAl复合涂层的温度场分布规律,探讨了超声振幅和扫描速度对温度场的影响。结果表明,超声振动作用下,温度梯度为零的范围更大,温度场分布更为均匀;超声振动有效降低了涂层中和界面结合区的温度梯度及残余应力;超声振幅越大,扫描速度越小,基材和涂层的温度越高,涂层至界面结合区之间的温度梯度越小。     

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.     

SiCf/SiC复合材料表面Si/Yb2Si2O7双层涂层结合强度分析

目的 通过选择合适的复合材料拉伸方向和涂层制备工艺,在SiCf/SiC复材上获得高结合强度的Si/Yb2Si2O7双层涂层.方法 采用真空等离子喷涂技术在2.5D编织的SiCf/SiC复合材料表面制备Si涂层、Si/Yb2Si2O7双层涂层.采用金相、XRD、SEM和EDS对试样进行表征,采用拉伸试验测试涂层的结合强度...     

Functionally graded carbon nanotubes/hydroxyapatite composite coating by laser cladding

Functionally graded carbon nanotubes/hydroxyapatite (CNTs/HA) composite coatings have been fabricated by laser cladding technique using CNTs/HA composite powders. As the feedstock for laser deposition, CNTs/HA composite powders were prepared by ball-milling different weight ratios (1%, 3% and 5%) of CNTs with HA powders. CNTs/HA composite coatings were fabricated with CNTs/HA composite powders and functionally graded coating was fabricated by sequentially depositing different CNTs/HA composite coatings on pure titanium. The phase composition, microstructure, micro-hardness, bonding strength and in vitro cellular responses of the composite coatings and the functionally graded composite coating were studied. The results show that the crystallinity of CNTs/HA composite coatings increased with increasing amount of CNTs in the powder mixture. The CNTs were dispersed homogeneously in the coatings to form an interconnected web and the cylinder graphic structure of CNTs was not changed after laser irradiation. Compared with pure HA coating, the maximum increase of the micro-hardness of CNTs/HA composite coatings was 46.8% and the micro-hardness of the functionally graded coating increased gradually through the thickness of this coating. Furthermore, the bonding strength of the functionally graded coating was nearly twice higher than that of pure HA coating. The in vitro cellular biocompatibility tests reveal that the functionally graded composite coating has comparable in vitro bioactivity with pure HA coating.