等离子喷涂法改善焊接结构的疲劳性能

采用低碳钢涂层对1Cr18Ni9Ti不锈钢横向与纵向角焊缝接头进行喷涂处理,测试了涂层的显微硬度和结合强度,并分别在焊接状态和喷涂处理状态下进行疲劳对比试验.试验结果表明,等离子喷涂层的显微硬度、结合强度约为火焰喷涂层的2倍.等离子喷涂后1Cr18Ni9Ti接头疲劳性能明显改善.横向接头焊接状态试件的疲劳强度为169.8 MPa,火焰喷涂试件为186.2 MPa,等离子喷涂试件为213.8 MPa,与焊接状态试件相比,等离子喷涂试件的疲劳强度提高25.9%,火焰喷涂试件提高9.7%.纵向接头焊接状态试件的疲劳强度为91.1 MPa,等离子喷涂试件为100.4 MPa,等离子喷涂后疲劳强度提高10.2%.     

Wear behavior of low-pressure plasma-sprayed AlCuFe quasicrystalline coating on titanium alloy

The wear-resistant AlCuFe quasicrystalline coating was fabricated on substrate of titanium alloy by low-pressure plasma-spraying (LPPS) method. The LPPS AlCuFe quasicrystalline coating has a rapidly solidified lamellar microstructure consisting of mainly icosahedral phase and small amount of cubic phase peaks. The results showed that AlCuFe quasicrystalline coating improved the wear resistance of titanium-based alloys under dry sliding wear test conditions. The excellent wear resistance may be attributed to the high hardness of AlCuFe quasicrystal and the formation of the tribofilm.     

等离子喷涂纳米Al2O3/Ni复合涂层的组织和耐磨性能研究

将纳米Al2O3颗粒和镍基粉用湿法混合,采用等离子喷涂工艺制备了复合涂层。利用SEM和TEM分析了Al2O3复合涂层的表面形貌和微观组织,用磨粒磨损试验机进行磨损试验,研究了纳米Al2O3的体积分数、粒径对涂层喷焊性和耐磨粒磨损性能的影响。结果表明,Al2O3复合涂层的表面形貌细腻,颗粒加入能有效改善弥散相与镍基涂层的相容性,当纳米Al2O3的体积分数为2.0%时,涂层的耐磨性能最好为镍基涂层的2倍多,在相同的体积分数下,随着涂层中弥散强化相尺寸减小,涂层的耐磨性提高。     

Effects of microstructure and properties on parameter optimization of boron carbide coatings prepared using a vacuum plasma-spraying process

This study employed artificial intelligence methods such as the Taguchi Method to determine the optimal parameters for boron carbide (B₄C) coatings using a vacuum plasma spray technique. We determined the optimal parameters to produce coatings and investigated B₄C coatings in an electromagnetic radiation environment by observing and analyzing changes in the microstructure and properties. These artificial intelligence methods comprised two stages. In the first stage, orthogonal arrays (OA) were used to distribute test parameters, and the Taguchi Method was used to optimize the parameters. In the second stage, a specimen of boron carbide coating was evenly exposed to radiation to investigate the microstructure and properties of the coating. The coating irradiated at a wavelength of 10.6 μm did not undergo any change in phase. The microstructure of the surface coating exhibited cracks, but these were insignificant. As the irradiation time increased, the number of cracks on the surface increased significantly. In addition, because the growth of surface cracks was governed by irradiation time, it was inferred that the growth was thermal efficiency-controlled (i.e., only generated by heating effects). Additionally, under irradiation, the surface of the boron carbide coating became oxidized and formed B₂O₃, H₃BO₃, and amorphous carbon; the coating size increased proportionally with irradiation time and weight of oxidation. The initial oxidation of the coating was classified as surface controlled, and the oxidation that formed on the B₂O₃ surface gradually transformed into extended controlled oxidation. Both types of oxidation control were conducted simultaneously, causing the weight of B₂O₃ to increase linearly. Two processes were involved in the extended control of oxidation: the formation of B₂O₃ (the cause of weight gain), and the vaporization of B₂O₃ (the cause of weight loss).     

等离子喷涂纳米陶瓷涂层研究

从纳米喂料的制备、纳米陶瓷涂层的制备及其结构和特性三方面评述了等离子喷涂纳米陶瓷涂层研究的进展,探讨了等离子喷涂纳米陶瓷涂层研究中存在的主要问题,并展望了等离子喷涂纳米陶瓷涂层的发展前景。     

New material concepts for the next generation of plasma-sprayed thermal barrier coatings

In application as a thermal barrier coating (TBC), partially stabilized zirconia (Zr) approaches some limits of performance. To further enhance the efficiency of gas turbines, higher temperature capability and a longer lifetime of the coating are needed for the next generation of TBCs. This paper presents the development of new materials and concepts for application as TBC. Materials whose compositions have the pyrochlore structure or doped Zr are presented in contrast with new concepts like nanolayers between the top and bond coat, metal-glass composites, and double-layer structures. In the last concept, the new compositions are used in a combination with Zr, as a double, multi, or graded layer coating. In this case, the benefits of Zr will be combined with the promising properties of the new top coating. In the case of metal-glass composites, the paper will be focused on the influences of different plasma spraying processes on the microstructure. The performance of all these different coating systems has been evaluated by burner rig tests. The results will be presented and discussed.     

Microstructures and characterization of zirconia-yttria coatings formed in laser and hybrid spray process

Hybrid plasma spraying combined with yttrium-aluminum-garnet laser irradiation was studied to obtain optimum zirconia coatings for thermal barrier use. Zirconia coatings of approximately 150 μm thickness were formed on NiCrAlY bond coated steel substrates both by means of conventional plasma spraying and hybrid plasma spraying under a variety of conditions. Post-laser irradiation was also conducted on the plasma as-sprayed coating. The microstructure of each coating was studied and, for some representative coatings, thermal barrier properties were evaluated by hot erosion and hot oxidation tests. With hybrid spraying, performed under optimum conditions, it was found that a microstructure with appropriate partial densification and without connected porosity was formed and that cracks, which are generally produced in the post-laser irradiation treatment, were completely inhibited. In addition, hybrid spraying formed a smooth coating surface. These microstructural changes resulted in improved coating properties with regard to hardness, high temperature erosion resistance, and oxidation resistance. This paper originally appeared in Thermal Spray: Meeting the Challenges of the 21st Century; Proceedings of the 15th International Thermal Spray Conference, C. Coddet, Ed., ASM International, Materials Park, OH, 1998. This proceedings paper has been extensively reviewed according to the editorial policy of the Journal of Thermal Spray Technology.     

以纳米SiC为填料的激光重熔等离子喷涂陶瓷涂层组织及耐腐蚀性能的研究

在45#钢表面,以等离子喷涂技术制备了WC/Co-NiCrAl涂层(TC-1)。采用激光直接重熔等离子喷涂陶瓷涂 层技术制备了激光重熔WC/Co-NiCrAl/laser-remelting陶瓷涂层(FC-2);以纳米SiC粉末为填料,对等离子喷涂层进行 了填料下的激光重熔,制备了纳米SiC改性的WC/Co-NiCrAl/nano-SiC复合陶瓷涂层(FC-3)。采用X射线衍射、扫描电 镜对三种涂层微观组织进行了分析,同时对陶瓷涂层的耐腐蚀性能进行了研究。结果表明,TC-1涂层由WC,W2C, W6C2.54,W,Co,CoO组成;TC-2重熔层由WC,W2C,CoO及W组成;纳米改性后的重熔层TC-3由SiC,Si2W,WC,W及 CoO组成。在激光作用下,原等离子喷涂层WC/Co的片层状组织得以消除。与TC-1涂层相比,TC-2及TC-3陶瓷涂层 致密化程度明显提高,涂层耐腐蚀性能也得到了明显的改善。     

Effects of Plasma-Sprayed Ceramic Coatings on the Strength Distribution of Silicon Carbide Materials

Sintered α-silicon carbide and siliconized silicon carbide tubular materials were plasma-spray coated with various ceramic oxides using conventional air plasma-spraying technology. The strength distributions of the coated tubes were evaluated by fracturing samples at room temperature using a c-ring test configuration. Changes in strength are explained using statistical treatments of the data, including a Weibull approach. Failure origins are characterized using fractography via scanning electron microscopy. The stength of plasma-spray coated SiC was equivalent or superior to that of as-received material, despite a surface pretreatment which induced surface flaws in the SiC substrate.     

TiAl合金表面等离子喷涂MCrAlY涂层热腐蚀行为研究

研究TiAl合金表面等离子喷涂NiCoCrAl-Y2O3涂层在850 ℃下对75%Na2SO4+25%NaCl熔盐的热腐蚀行为,及对TiAl金属间化合物抗高温热腐蚀性能的影响。研究表明,在850 ℃,等离子喷涂NiCoCrAl-Y2O3涂层由于生成Cr2O3,NiO和NiCr2O4等各种氧化物组成的氧化层,显著提高了TiAl基体的抗热腐蚀性能。在热腐蚀过程中,S元素以Ni元素为载体,逐步渗入涂层中,生成过渡产物Ni3S2。随着O分压的升高,反应进入了氧化阶段,生成Cr2O3、NiO等氧化物,随着两种物质含量的增加,最后发生固相反应,生成尖晶石结构的NiCr2O4化合物。过渡产物Ni3S2与腐蚀介质中的Cl-离子形成微电池,可以加快热腐蚀反应速度