等离子喷涂Al2O3-3%TiO2涂层结构及加载绝缘性能

目的研究等离子喷涂Al_2O_3-3%TiO_2涂层的抗低温冲击性能和外部载荷下的绝缘性能等综合性能,探讨大气等离子喷涂技术作为核聚变反应堆磁体支撑结构绝缘涂层制备方法的可行性。方法采用大气等离子喷涂技术在喷砂处理的A286基体上制备Al_2O_3-3%TiO_2涂层并进行封孔处理,利用XRD、SEM等手段对涂层的微观结构和常规性能进行表征,重点关注了涂层的低温热冲击性能和加载绝缘性能。结果喷涂粉末充分熔融及铺展而沉积为典型的层叠状结构,涂层的结合强度达30 MPa,孔隙率可控制在5%以内。均匀涂刷在涂层表面的硅树脂封孔剂有利于填充涂层孔隙和微裂纹,封孔剂在涂层内部的渗透深度可达到大约100μm。从室温水浴到液氮进行10个循环的热冲击试验后,涂层未发现裂纹和剥落,且热冲击对绝缘性能没有显著影响。250 MPa压缩载荷下,涂层的表面电阻率明显降低,但仍高于30 MΩ/sqr。结论 Al_2O_3-3%TiO_2涂层可作为高载荷和低温环境下使用的潜在绝缘材料,而大气等离子喷涂将成为制备核聚变反应堆磁体支撑结构关键部件绝缘涂层的重要选择。     

喷涂距离对热障涂层拉伸强度的影响

用等离子喷涂方法，在不同的喷涂距离（d）下制备出ZrO2陶瓷涂层，通过涂层的拉伸实验、X射线衍射和扫描电镜分析，研究了喷涂距离对涂层拉伸强度（σ）的影响规律。结果表明：d=70、80mm时，σ较高，最高可达9．14MPa；d〈70mm时，粘接层的氧化明显加剧，热生长氧化物的量明显增加，降低了ZrO2涂层与粘接层之间的结合强度，导致σ下降；d〉80mm时，随着喷涂粒子的速度降低，撞击到喷涂表面后不能完全铺展，导致σ下降。     

Copper-titanium diboride coatings obtained by plasma spraying reactive micropellets

Electrotribological applications require materials with both high electrical conductivity and wear resisance. For this purpose, a copper- base plasma sprayed coating containing titanium diboride particles was developed. The process for fabricating this CU- TiB₂ coating consists of plasma spraying reactive powders that contain a Cu- Ti alloy and boron. The reaction between the copper alloy and boron proceeds in different steps going from solid- state diffusion of titanium and copper to the synthesis of TiB₂ in a liquid below 1083 ‡C. Plasma sprayed copper coatings contain finer TiB₂ crystals than Cu- TiB₂ materials synthesized in a furnace at 1200 ‡C. Coatings with 25 vol% TiB2 have hardnesses that are comparable to Cu- Co- Be and Cu- Ni- Be alloys and to Cu- W and Cu- Mo alloys used in spot welding. Their low electrical resistivity of 52 ΜΩ cm could be increased by lowering the oxygen content with coatings and controlling the formation of TiB₂ clusters, the titanium content in solution in copper remaining low after the synthesis reaction.     

Microstructures and Properties of Laser-Glazed Plasma-Sprayed ZrO2-YO1.5/Ni-22Cr-10AI-1Y Thermal Barrier Coatings

Thermal barrier coatings (TBCs) consisting of two layers with various yttria contents (ZrO ₂- YO_1.5/Ni-22Cr-10Al- lY) were plasma sprayed, and parts of the various specimens were glazed by using a pulsed CO₂ laser. All the specimens were then subjected to furnace thermal cycling tests at 1100 °C; the effect of laser glazing on the durability and failure mechanism of the TBCs was then evaluated. From these results, two models were developed to show the failure mechanism of as- sprayed and laser- glazed TBCs: model A, which is thermal-stress dominant, and model V, which is oxidation-stress dominant. For top coats containing cubic phase, cubic and monoclinic phases, or tetragonal and a relatively larger amount of monoclinic phases, whose degradation is thermal- stress dominant, laser glazing improved the durability of TBCs by a factor of about two to six. Segmented cracks that occurred during glazing proved beneficial for accommodating thermal stress and raising the tolerance to oxidation, which resulted in a higher durability. Thermal barrier coatings with top coats containing tetragonal phase had the highest durability. Degradation of such TBCs resulted mainly from oxidation of the bond coats. For top coats with a greater amount of monoclinic phase, thermal mismatch stress occurred during cooling and detrimentally affected durability.     

热喷涂技术及其设备应用

阐述了热喷涂潦方法和技术特性；比较了几种常用的热喷涂技术的优缺点．如火焰喷涂、电弧丝喷涂、等离子喷涂等．介绍了相应的设备系统的组成、应用领域及其发展的新趋势。指出合理使用热喷涂技术，不仅可以有效利用材料。还能扩展零部件的用途和延长使用寿命，从而创造出巨大的经济效益和社会效益。     

Molybdenum and tungsten coatings for x- ray targets obtained through the low-pressure plasma spraying process

Low-pressure plasma spraying under an argon atmosphere was employed to deposit molybdenum and tungsten coatings on different metallic, ceramic, and composite substrates. Molybdenum coatings ob-tained through this technique presented a homogeneous structure with an average porosity of about 17 %. These coatings exhibited adhesion greater than 40 MPa on molybdenum and grey cast iron (FT25) substrates. No adhesion was observed on an A1N surface regardless of the preheating temperature and/or surface preparation. Adhesion on AIN-Mo (AM25) composite substrate, containing 25 % dispersed metal-lic phase by volume, showed intermediate results. Tungsten coatings exhibited porosity between 10 to 12% and a typical lamellar structure. The adhesion of tungsten coatings on molybdenum and FT25 sub-strates was around 40 MPa.     

Plasma spray forming of functionally graded materials mould

A new technology of functionally graded materials(FGM) mould fabricated by plasma spraying and arc spraying was developed. According to applied characteristic of plastic mould, the reasonable coatings of FGM were designed and their microstructures were analyzed. At the same time, some key problems were solved including spray mould fabricating, FGM forming and demoulding, etc. The results show that the service performance of the FGM mould is much more excellent than the one composed of the traditional materials, and the life span can also be greatly increased. The technology will have a significant influence on materials development in mould industry.     

Effect of Ti-OH formation on bioactivity of vacuum plasma sprayed titanium coating after chemical treatment

The effect of Ti-OH groups on bioactivity of NaOH treated titanium coating was investigated in this paper. The NaOH-heat treatment was also applied to modify the titanium coating for comparison. The results show that the amount of Ti-OH groups was important to induce apatite formation on the treated titanium coating. When the NaOH treated titanium coating was exposed to SBF, it released Na⁺ ions from the sodium titanate layer on its surface into the SBF via exchanging with H₃O⁺ ions in the fluid and Ti-OH groups were rapidly formed on the surface. So the NaOH treated titanium coating has good bioactivity in simulated body fluid (SBF). The amount of Ti-OH groups on the titanium coating was reduced after heat treatment, so the bioactivity of NaOH-heat treated titanium coating was obviously affected.     

铸铁坩锅抗铝融蚀等离子喷涂技术

针对提高化铝用铸铁坩埚抗融蚀寿命的实际问题,选用价格较低、耐高温、抗融蚀性好的Ａｌ２Ｏ３陶瓷材料作为坩埚内壁的工作层,采用等离子喷涂技术来提高其抗融蚀性。但由于Ａｌ２Ｏ３陶瓷涂层的致密性差、结合强度及抗热震寿命低等缺点,不适宜化铝坩埚在７２０℃长时间加温,且液铝呈搅拌行为的工作条件下使用。本文在Ａｌ２Ｏ３喷涂粉末中加入１３％ＴｉＯ２,促使涂层的组织结构发生变化,提高了涂层的结合强度,改善了涂层的致     

超薄基体气门等离子喷焊T400合金层的试验研究

采用等离子喷焊方法在厚度为1mm的气门锥面制备了钴基合金涂层，用X射线衍射仪分析了涂层的相结构，用电子探针分析了涂层截面的成分分布，用光学显微镜观察了涂层的组织形貌。结果表明，熔合区主要由细小的等轴晶和少量的柱状晶组成，涂层主要由铸态枝晶和细晶组成，在涂层与基体之间形成了明显的冶金结合层。涂层中的金属元素呈梯度分布，在界面处存在明显的热扩散现象。实际应用表明，由于喷焊层形成了合金固溶体和耐磨性能好的碳化物，因而提高了气门的使用性能。