碳钢表面激光熔敷镍基碳化钛涂层组织特征

利用Ni60自熔合金粉末、TiFe粉、石墨、CaF_2和稀土经适当比例混合后采用激光熔敷技术制备TiC/Ni基涂层,同时研究对熔敷涂层宏观形貌、显微组织、微观形貌、物相结构及硬度的影响。结果表明:经激光熔敷可在镍基涂层中形成陶瓷硬质相TiC,熔敷涂层表面光滑平整;熔敷层底部与基体的结合处有一条白亮带,熔敷层组织由Ti C,Fe3Ni,NiO等相组成,TiC颗粒以球状、团聚状和花瓣状分布于(Ni,Fe)固溶体;熔敷层硬度分布较均匀,硬度为HV_(0.2)550~HV_(0.2)650,明显高于基体硬度HV0.2240~HV0.2260。     

Q235钢表面纳米陶瓷涂层性能的研究进展

综述了近年来Q235钢表面制备纳米陶瓷涂层的研究进展,介绍了热喷涂法、熔敷法、热化学反应法、多元复合化学镀等技术的研究成果,分析了各种制备技术的优缺点,并展望了今后Q235钢表面制备纳米陶瓷涂层的发展方向.     

铝表面激光熔覆陶瓷原理和工艺的研究

研究了激光熔覆陶瓷的物理过程，发现原来熔覆合金的模型不符合激光熔覆陶瓷的情况，提出了新的激光熔覆模型，研究了激光熔覆工艺参数对陶瓷涂层质量的影响，得出了获得良好涂层的工艺条件，在铝基体表面成功地获得了均匀致密的ＳｉＯ２涂层和Ａｌ２Ｏ３涂层，涂层内部致密无缺陷，涂层与铝基体结合良好。     

等离子重叠熔敷对Fe-Cr-C-Ti涂层性能的影响

由于材料的磨损性能与其组织关系密切,因此重叠熔敷涂层的制备方法对涂层磨损性能也有着重要影响. 在前期试验基础上制得等离子一层、二层和三层重叠熔敷涂层,采用SEM等观察了重叠熔敷涂层的显微组织和磨损形貌,用半自动显微硬度计进行硬度测试,用磨损试验机测试计算了涂层的摩擦系数,并通过比较3种重叠熔敷涂层的组织和磨损性能,探讨了重叠熔敷工艺对涂层磨损性能的影响,以指导涂层的制备工艺. 结果表明,随着重叠熔敷层数的增加,涂层摩擦系数降低,耐磨性能和载荷特性显著提高.     

Fe-Ti-B激光熔敷层中TiB2晶须的原位合成

为了降低激光熔敷Fe-B涂层的高度脆性，使用不同成分的B4C和Fe-Ti合金混合粉末在奥氏体不锈钢基体上进行了激光熔敷，得到了具有TiB2晶须强化的复合Fe-Ti-B涂层。该涂层在保持原来Fe-B涂层的高硬度的同时，其抗裂性能亦得到了改善。     

TIG熔敷原位合成TiB_2复合陶瓷增强熔敷层

利用TIG熔敷预置Ti,Si,B4C的金属陶瓷混合粉末,在低合金钢表面直接原位合成陶瓷增强的铁基合金复合涂层,获得了与基体呈良好冶金结合的熔敷层。XRD和SEM的分析结果表明,熔敷层形成的陶瓷增强相主要为Ti B2,Fe2B和Ti C增强相;Ti B2,Ti C增强相在界面区呈细小点状分布,在过渡区和近表面区呈短杆状和长杆状分布。Fe2B大量分布于熔覆层的界面区和过渡区,并与Fe的固溶体形成Fe2B+α(Si)共晶组织。陶瓷硬质相的形成,使熔敷层的显微硬度有了明显提高,熔覆层近表面区平均显微硬度可达13.53 GPa,为基体的6倍。     

氩弧熔敷原位反应WC硬质陶瓷涂层结构与界面分析

氩弧熔敷原位反应技术具有熔覆快、操作简单,并与基体保持良好的润湿性和结合强度等特点,已成为国内外表面强化技术的热点之一。本文以钨铁和石墨作为原位合成WC涂层的原料,运用氩弧焊技术提供热源在Q235钢基材表面熔敷一层性能优良的耐磨硬质陶瓷涂层。利用扫描电镜、X衍射仪等实验仪器对涂层与基体界面进行分析,研究结果表明,涂层与基体之间呈冶金结合,涂层结构主要由稳定相和亚稳定相构成,在涂层与基体元素互扩散中,Fe向熔覆层扩散的程度比W向基体扩散更为明显,而且在界面中的WC会偏聚集于基体一边。     

激光熔覆陶瓷涂层的研究现状及发展

论述了激光熔覆陶瓷涂层的特点,分析了激光熔覆陶瓷涂层的发展历程及存在的主要问题,总结了当今激光熔覆陶瓷涂层的主要研究方向.     

钢表面光束熔敷镍基耐磨合金技术

采用自行研制的光束加热设备和辅助工装,实现了在４５＾＃钢表面熔敷镍基＋ＷＣ耐磨合金涂层工艺过程。熔敷敷层的微观组织与硬度分析表明,涂层与基材产生了良好的冶金结合,熔敷层的宏观及显微硬度较基材均有提高,预示着光束熔敷的镍基合金涂层的有较好的耐磨性能。     

激光熔敷NiTi/Ni3Ti金属间化合物复合材料涂层组织及耐磨性

以Ni79Ti21（wt％）合金粉末为原料，采用同步送粉激光熔敷技术在BT20钛合金表面制备出NiTi／Ni3Ti金属间化合物复合材料涂层，分析了该涂层的显微组织，测试了该涂层的室温干滑动磨损性能。结果表明，激光熔敷涂层组织均匀致密，与基材呈良好的冶金结合，具有优良的抗滑动磨损性能。     

大气等离子喷涂热障涂层CMAS防护层成分及厚度优化

目的优化热障涂层(TBCs)CMAS(CaO-MgO-Al_2O_3-SiO_2)阻抗层的成分和厚度,使其能有效阻抗CMAS沉积物的腐蚀,并同时与热障涂层有较高的结合力。方法首先利用多孔无压烧结陶瓷块体研究了不同含量Al_2O_3和8YSZ(8wt.%氧化钇稳定氧化锆)均匀混合后在高温(1250℃)条件下对CMAS沉积物的防护作用。采用扫描电子显微镜(SEM)、能谱仪(EDS)以及X射线衍射(XRD)仪,分析研究了CMAS腐蚀层的显微结构、腐蚀深度及反应产物。其次,基于最优成分,利用大气等离子喷涂(APS)制备了具有8YSZ/Al_2O_3陶瓷层的热障涂层。对CMAS腐蚀厚度进行分析测量,提出CMAS阻抗层的厚度。结果 Al_2O_3的添加可以有效地阻碍CMAS的渗入,并且Al_2O_3含量越多,防护效果越好。但是CMAS的渗入深度和氧化铝的添加量呈非线性关系。结合TBC陶瓷层的热学性能和力学性能的要求,本实验中最佳的TBCs复合陶瓷层组分为70wt%8YSZ+30wt%Al_2O_3。基于实验结果,提出YSZ/Al_2O_3复合陶瓷层(50μm)-YSZ陶瓷层(150μm)的双层TBC陶瓷层结构,并综合计算出复合陶瓷层的热膨胀系数为9.93×10-6℃-1以及双层TBC陶瓷层的热导率为2.4 W/(m·K)。最后对Al_2O_3减缓CMAS腐蚀的机理进行了量化分析。结论 YSZ/Al_2O_3复合阻抗层的最优成分为70wt%8YSZ+30wt%Al_2O_3,厚度为50μm,能有效阻碍高温下CMAS腐蚀。     

SHS-离心法陶瓷衬管致密性的提高

采用自蔓延高温合成技术(SHS法)与离心技术相结合，在普通碳素钢管的内壁复合上一层均匀的陶瓷层，制成金属—陶瓷复合管。利用X射线衍射和扫描电镜进行陶瓷层的组织结构、相组成和成分分析，并测定了陶瓷层的密度、硬度和耐磨性能。结果表明，适量添加S502，在陶瓷的凝固和致密化过程中，降低了反应凝固终了温度，延长了陶瓷的熔融时间，提高了陶瓷层液相的流动性，加速了气体排除，陶瓷层的致密性得到提高。     

熔-喷ZrO2+WC陶瓷涂层组织结构

采用熔-喷技术，对ZrO2、WC及ZrO2 WC四种混合陶瓷粉末制备的涂层，通过光学显微镜、扫描电镜、能谱分析等手段，对涂层的组织结构进行了分析研究。发现采用熔-喷技术制备的陶瓷涂层，涂层与母材呈熔焊状态，涂层发生了冶金反应，具有重熔的特点，涂层呈现出梯度涂层的特征，表层具有喷涂材料的组织结构，中间层具有母材与喷涂材料共有的组织结构。因此大大地提高了涂层的结合强度，明显地改善了涂层的组织性能，使涂层变得均匀致密，从而拓宽了陶瓷材料的应用范围。     

微弧氧化陶瓷层后处理技术的研究现状及展望

微弧氧化陶瓷层表面孔隙的存在加速了陶瓷层的腐蚀,后处理技术有效地提高了微弧氧化陶瓷层的耐蚀性、耐磨性和功能性。本文介绍了水热处理、溶胶凝胶技术、化学镀和有机涂覆技术等在微弧氧化陶瓷层后处理中的应用情况,展望了微弧氧化陶瓷层的后处理技术的发展方向和前景。     

Preparation of ceramic coatings on inner surface of steel tubes using a combined technique of hot-dipping and plasma electrolytic oxidation

A new method for inner surface modification of steel tubes, named a combined technique of hot-dipping and plasma electrolytic oxidation (PEO) was proposed and demonstrated in this paper. In this work, metallurgically bonded ceramic coatings on inner surface of steel tubes were obtained using this method. In the combined process, aluminum coatings on steel were firstly prepared by the hot-dip process and then metallurgically bonded ceramic coatings were obtained on the aluminum coatings by PEO. The element distribution, phase composition and morphology of the aluminide layer and the ceramic coatings were characterized by SEM/EDX and XRD. The corrosion resistance of the ceramic coatings were also studied. The results show that, after hot-dip treatment, the coating layers consist of two layers, where Al, Fe_xAl _(1−x) were detected from external topcoat to the aluminide/steel substrate. Then after PEO process, uniform Al₂O₃ ceramic coatings have been deposited on inner surface of steel tubes. The ceramic coatings are mainly composed of -Al₂O₃ and γ-Al₂O₃ phase. The compound coatings show favorable corrosion resistance property. The investigations indicate that the combination of hot-dipping and plasma electrolytic oxidation proves a promising technique for inner surface modification of steel tubes for protective purposes.     

Joining of C<Subscript>f</Subscript>/SiC Ceramics to Nimonic Alloys

C_f/SiC ceramic composites have been brazed to Nimonic alloys using TiCuAg filler metal. In order to improve wettability and to provide compatibility between ceramic and metal, the C_f/SiC surface was metallized through the deposition of a chromium layer. Subsequent heat treatments were carried out to develop intermediate layers of chromium carbides. Excellent wetting of both the composite ceramic and the metal from the filler metal is observed in the fabricated joints. Shear tests show that failure occurs always within the ceramic material and not at the joint. In the filler region depletion of Ti and formation of Ag and Cu rich regions are observed. At the C_f/SiC-filler interface a layered structure of the filler metallic elements is observed. Titanium interacts with the SiC matrix to form carbides and silicides.     

Protective adhesive zirconium oxide coatings

Modern technologies of application of paint or polymer protective coatings on metal surfaces require previous application of adhesive phosphate coatings on them to provide reliable adhesion. Among the known disadvantages of phosphating processes are their high energy content and the rather complex equipment needed for implementation of the processes, while the processes themselves require strict control because the properties of the resulting coatings depend strongly on parameters such as free and total acidity, temperature, and concentration of accelerators. In some cases, nanosized ceramic zirconium oxide adhesion coatings can be an alternative to adhesive phosphate layers. A solution has been prepared and parameters of the process have been determined allowing one to precipitate nanosized ceramic zirconium oxide coatings that satisfy the requirements for adhesive layers under paint coatings. It has been found that the resulting coatings are not inferior in their protective characteristics to amorphous phosphate and silicone coatings.     

Effects of Al3+ concentration in hydrothermal solution on the microstructural and corrosion resistance properties of fabricated MgO ceramic layer on AZ31 magnesium alloy

Porous magnesium oxide (MgO) ceramic layers were prepared on AZ31 magnesium alloy via microarc oxidation (MAO) and sustained hydrothermal treatment at 90°C for 18 h in alkaline zinc nitrate solution with varying Al³⁺ concentrations. Increasing the Al³⁺ concentration advanced the formation of layered double hydroxide (LDH) films on the MgO ceramic layers, enabling the sealing of micropoles and cracks via in situ growing. Electrochemical and immersion test results indicated that the MAO/hydrothermal treatment-prepared LDH/MgO composite coatings achieved increased corrosion resistance than single MAO ceramic layers, due to the sealing effect and ion-exchange capacity of LDHs. Furthermore, as Al³⁺ concentration in hydrothermal solution increased, the anticorrosion properties of the composite coatings were enhanced. Concludingly, LDH/MgO composite coatings could provide augmented long-term anticorrosion protection for magnesium alloys compared with single MAO ceramic layers.     

Development of porous ceramic layers through sublimation of metal phases in multiphase alloys

Here described is a procedure for the fabrication of porous ceramic layers onto metallic substrates. Porous ceramic layers with submicron sized pores can readily develop by taking advantage of eutectic solidification and sublimation of a metallic phase upon high temperature exposure. The material in the present study is based on the Ir–Y system, where two-phase microstructures comprised of Ir and Ir₃Y are formed through solidification process. A eutectic solidification yields submicron-scaled Ir particles within the Ir₃Y matrix. Upon air-exposure at 1373 K, the Ir phase forms volatile oxides and the Ir₃Y phase transforms into Y₂Ir₂O₇, by which porous ceramic layers develop on the surface of the base materials.     

Recent Developments in the Field of Thermal Barrier Coatings

Conventional thermal barrier coating (TBC) systems consist of a duplex structure with a metallic bondcoat and a ceramic, heat-isolative topcoat. Several recent research activities are concentrating on developing improved bondcoat or topcoat materials; for the topcoat especially, those with reduced thermal conductivity are investigated. Using advanced topcoat materials, the ceramic coating can be further divided into layers with different functions. One example is the double-layer system in which conventional yttria-stabilized zirconia (YSZ) is used as bottom and new materials such as pyrochlores or perovskites are used as topcoat layers. These systems demonstrated an improved temperature capability compared to standard YSZ. In addition, new functions are introduced within the TBCs. These can be sensorial properties that can be used for an improved temperature control or even for monitoring remaining lifetime. Further increased application temperatures will also lead to efforts for a further improvement of the reflectivity of the coatings to reduce the radiative heat transfer through the TBC.