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Corrosion Behavior of Vanadium Carbide Coating Produced by a Thermal Diffusion Process 总被引:2,自引:0,他引:2
S. Bhagga Fazluddin A. Koursaris C. Ringas K. Cowie 《Materials and Manufacturing Processes》1995,10(2):159-169
Vanadium carbide coating was deposited on carbon steel (EN9) and mild steel using a thermal diffusion process. Samples were immersed in a molten salt bath containing appropriate carbide forming compounds at temperatures ranging from 850°C to 1100°C. Samples were treated for various lengths of time in order to obtain coatings of various thicknesses. The corrosion behavior of the vanadium carbide coatings was evaluated by accelerated electrochemical tests. The corrosion resistance of the carbide coating was found to be superior to that of the untreated base alloys. 相似文献
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Microstructure plays a predominant role in determining material behaviour. Increasing microstructure uniformity has long been considered a fruitful means of improving thermal, chemical and mechanical properties of the materials. High velocity oxy-fuel (HVOF) is one of the emerging technologies among the thermal spraying techniques, for producing uniform and dense coatings, having high hardness and good adhesion values. In this study, HVOF technique was used to deposit NiCrBSi coatings, approximately 250-300 μm thick, on the Ni- and Fe-based superalloys for hot corrosion applications. The coatings were characterised in relation to coating thickness, porosity, microhardness and microstructure. The hot corrosion behaviour of the coatings deposited on nickel-based superalloys after exposure to molten salt (Na2SO4-60% V2O5) at 900 °C under cyclic conditions was also studied. The techniques used in the present investigation include X-ray diffraction, optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX) and electron probe microanalysis (EPMA). The thermogravimetric technique was used to establish kinetics of corrosion. The structure of the as sprayed NiCrBSi coating mainly consisted of γ-nickel solid solution containing small fraction of Cr7C3 and Ni3B phases. Very weak peaks of NiCr2O4 spinel oxides were also formed during spraying of the coatings. Some porosity (less than 1.4%) and inclusions were observed in the structure of the coatings. Coating microhardness values were found to be in the range of 750-930 Hv (Vickers Hardness) on different substrates. The NiCrBSi coating was found to be very effective in decreasing the corrosion rate in the given molten salt environment at 900 °C. The hot corrosion resistance imparted by NiCrBSi coatings may be attributed to the formation of oxides of silicon, chromium, nickel and spinels of nickel and chromium. 相似文献
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采用超声空蚀与电化学测试相结合的方法,对AC-HVAF热喷涂非晶金属和金属陶瓷两种涂层在水力压裂液中的空蚀及交互作用规律进行了研究,分析了耐蚀性和硬度在空蚀时的主导作用,确定了空蚀机理。结果表明,压裂液中KCl恶化了涂层的腐蚀性能,进而影响了空蚀行为。涂层在压裂液中的抗空蚀性能是耐蚀性与硬度结合的双变量函数。空化的力学破坏对高硬度涂层的空蚀过程有显著影响,硬度相对较高的金属陶瓷防护涂层的抗空蚀性能优异。压裂工况下,AC-HVAF涂层空蚀损伤是由于气泡溃灭垂直冲击孔隙或缺陷区域,硬相直接被剥离表面。降低孔隙和提高粘结相结合强度有助于提高涂层在压裂液中的抗空蚀性能。 相似文献
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SiCP/AZ31镁基复合材料微弧氧化膜结构与性能分析 总被引:1,自引:0,他引:1
采用微弧氧化表面处理技术在SiC颗粒增强AZ31镁基复合材料表面制备保护性陶瓷膜.分析了陶瓷膜的表面形貌、截面组织和相组成,并测量了膜层的硬度、热震和电化学腐蚀特性.结果表明,陶瓷膜由MgO、Mg2SiO4和少量同电解液组成元素相关的相所组成,膜内还残留少量SiCP增强体.膜层的最高硬度可达到HV800,比复合材料基体提高五倍以上.经过100次热循环(500℃→水淬)后膜层与复合材料结合良好,显示该膜层有较好的抗热震性能.微弧氧化处理后,SiCP/AZ31镁基复合材料的抗腐蚀能力得到较大提高. 相似文献
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采用微弧氧化技术在5052铝合金表面制备蓝色陶瓷膜,研究Co(OH)_2着色剂浓度和微弧氧化电压对蓝色陶瓷膜组织结构和腐蚀性能的影响规律。采用光学显微镜、扫描电镜和X射线衍射研究蓝色陶瓷膜层的宏观形貌、微观组织和相结构,采用电化学工作站测试陶瓷层在3.5%(质量分数)NaCl溶液中的电化学腐蚀性能。研究结果表明,蓝色微弧氧化陶瓷层主要由γ-Al_2O_3组成,提高Co(OH)_2浓度或者氧化电压,膜层颜色由浅向深演变,当浓度增至3.0g/L后膜层蓝色不再加深,同时膜层表面逐渐封闭,致密性提高。在140V氧化电压下,添加1.0g/L Co(OH)_2所制备的蓝色膜层具有最好的耐腐蚀性能。蓝色膜具有颜色艳丽、装饰性好等优势,相信该蓝色微弧氧化膜技术在建筑材料和仪器仪表行业将会有广阔的应用前景。 相似文献
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Thermal spraying of vanadium carbide reinforced iron based HVOF sprayed cermet coatings for wear protection like WC‐Co(Cr) and Cr3C2‐NiCr have found a broad range of applications in the past. By using chromium containing matrices, they exhibit good corrosion resistance along with outstanding wear resistance. In present research in the area of powder metallurgy and PTA welding iron based alloys with high content of chromium and vanadium have been developed, revealing similar properties and therefore being a cost efficient alternative to established cermet coatings. HVOF sprayed coatings of these iron based alloys are investigated regarding their economic applicability and their corrosion and wear properties. 相似文献
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热障陶瓷涂层的最新发展 总被引:11,自引:2,他引:9
综述了现代航空发动机用热障陶瓷涂层的最新发展,着重介绍了双陶瓷层,电子束物理气相沉积(EB-PVD)和溶液等离子喷涂(SPS)纳米热障陶瓷涂层的性能和特点。 相似文献
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本工作研究了CO2激光重熔处理对超音速火焰喷涂WC--Co和WC--NiCr涂层的组织结构和摩擦学行为的影响。结果表明:选定优化参数下,激光重熔可降低涂层气孔率,提高涂层显微硬度,涂层与基材之间实现冶金结合;干摩擦条件下,涂层经过激光重熔处理耐磨性能显著提高;但润滑条件下劣于未经重熔处理涂层,这可能与未重熔涂层含有较多的气孔,可存储润滑油较好地发挥润滑效果有关。 相似文献
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通过调整电解液中硅酸钠的浓度, 利用等离子体电解氧化(PEO)技术在铝合金LY12表面制备了各种陶瓷涂层, 利用光学显微镜、XRD、电化学阻抗谱(EIS)对涂层的形貌、成分和涂层在NaCl溶液中耐腐蚀性能进行了研究. 结果表明: 提高电解液中硅酸钠的浓度可以使得涂层的总厚度增加, 但过高或过低的浓度都会导致致密层厚度的减薄. 当浓度为20g/L时, 所制备的涂层的成分以氧化铝为主; 当浓度为40g/L时, 涂层的成分主要是莫来石和氧化铝; 当浓度超过60g/L 时, 涂层的成分主要为非晶相. EIS的研究表明, 涂层耐腐蚀性取决于涂层中的致密层, 增加致密层的厚度可以提高PEO涂层的耐腐蚀性, 在中性、酸性、碱性腐蚀介质中, PEO涂层都显示出对基体良好的保护作用. 相似文献
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介绍一种新型陶瓷转化工艺在空调镀锌钢板的粉末喷涂中的应用.通过转化膜的晶相、附着力及盐雾试验表征,对预转化板的现有工艺进行控制.盐雾试验结果表明,预转化镀锌钢板经过弱碱性脱脂剂清洗,经陶瓷转化后与粉末涂料结合,可以得到良好耐蚀性和附着力强的膜层. 相似文献
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There are a lot of technologically interesting characteristics of glass–ceramics, which are hard, wear resistant, oxidation and corrosion resistant ceramic materials. In the present study, the production of the basalt-based glass–ceramic coating by atmospheric plasma spray technique and their structural characterization were reported. Basalt-based glass coating was performed on AISI 1040 steel substrate which was pre-coated with Ni–5 wt% Al by using plasma spray gun. Basalt coatings of the glass form were crystallized at 800, 900 and 1000 °C for 1–4 h in orders to transform to the glass–ceramic structure. The presence of augite [(CaFeMg)SiO3], diopside [Ca(Mg0.15Fe0.85)(SiO3)2] and aluminian diopside [Ca(Mg,Al)(Si,Al)2O6] crystalline phases formed in the basalt-based glass–ceramic coating layer was detected by X-ray diffraction analysis. Optical microscopy with micrometer was used for metallographic examinations. Differential scanning calorimeter was used for determining the crystallization temperature of glass form basalt-based coatings. Microhardness measurements were carried out on the basalt-based glass–ceramic coating layer with Vickers indenter. The hardness of coating layers is changing between 1009 and 1295 HV0.05 depending on crystallization temperature and process times. It was found that, the higher the crystallization temperature, the more the crystalline phases were resulted. In addition, the lower the crystallization temperature and the longer the treatment time, the harder the coating layer became. 相似文献
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目的以FeCoCrMoCBYS非晶粉末为喷涂材料,采用几组不同的热输入量,使用超音速火焰喷涂(HVOF)制备成铁基非晶涂层,通过对涂层性能进行分析,研究热输入量对涂层的影响。方法通过调整煤油流量和氧气流量两个参数来控制喷涂时的热输入量。分别利用扫描电镜(SEM)、X射线衍射分析仪(XRD)、差示扫描量热仪(DSC)、维氏显微硬度计等设备,研究热输入量对涂层显微组织和显微硬度的影响,并通过电化学工作站测试涂层在1 mol/L FeCl_2溶液中的极化曲线进而分析其耐蚀性能。结果不同热输入量下制备的涂层均具有较高的非晶含量。保持其他参数不变,随着热输入量的增加,涂层变得更加致密,孔隙率最小达到1.56%。涂层显微硬度先增大后减小,涂层横截面中部位置硬度大于表面和接近基体位置。结论当热输入量达到6.4×10~5 J时,非晶含量高达96.7%,自腐蚀电流密度低,耐腐蚀性最好。 相似文献