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In this study, the effect of post-spray heat treatment on the microstructure, microhardness, and adhesive strength of the
cold-sprayed Ti coating was investigated. It was found that a thick and relatively porous Ti coating was deposited by cold
spraying. The coating surface layer presented a more porous structure. The microhardness of the as-sprayed Ti coating was
slightly higher compared to pure Ti bulk, owing to the work hardening effect during deposition. After annealing at 850°C for
4 h under vacuum condition, the Ti coating also presented a porous structure with more uniformly distributed small pores.
A metallurgical bonding between the deposited particles was formed through annealing treatment. The adhesive strength of coating
was significantly improved after annealing. The microhardness of the annealed Ti coating was also increased. 相似文献
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《Ceramics International》2021,47(23):33338-33352
Niobium carbide composite coatings were prepared on titanium alloy surface by plasma spraying NbC–Al2O3, Nb–SiC and Nb–SiC–Al composite powders, respectively. The phase composition, microstructure and formation mechanism of the three composite coatings were analyzed and their microhardness, toughness and scratch resistance were compared. The phases of the NbC–Al2O3 system did not change during the plasma spraying process, and new phases (Nb2C, NbC and Nb3Si) were formed in the Nb–SiC and Nb–SiC–Al systems. TEM results of the Nb–SiC composite coating indicate that the new phases nanocrystalline Nb2C, submicron NbC and nanocrystalline Nb3Si were formed during the plasma spraying process. Compared with the NbC–Al2O3 composite coating, the microstructure of the Nb–SiC and the Nb–SiC–Al composite coatings were uniform, and the porosity were relatively low, and the hardness was higher. The Nb–SiC–Al composite coating was denser than the Nb–SiC composite coating, the lamellar structure was obvious and the number of pores in the coating was the least, which is attributed to the better molten state of the composite powder by the addition of the Al to the Nb–SiC system. The Nb–SiC–Al composite coating had better toughness and scratch resistance. 相似文献
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防氧化脱碳涂料对钢铁材料热处理的保护研究 总被引:3,自引:0,他引:3
分别研究了硅酸盐防氧化脱碳涂料对45#钢和40Cr钢热处理时的保护效果。1 100℃下保温时间对钢样氧化失重率的影响实验表明,随着保温时间的延长,无涂料保护的钢样的氧化失重率迅速增大,但有涂料保护的钢样其氧化失重率变化不大。钢样经1 100℃×2 h热处理后油淬的金相照片显示,45#钢的氧化脱碳程度比40Cr钢更严重,而有涂料保护的钢样其氧化脱碳作用明显减少。经过860℃×4 h与1 100℃×4 h热处理后淬火脱落的涂层其截面SEM形貌显示,涂层的内侧出现较厚的致密层,并呈明显的烧结状态,由能谱分析可知,它应为基体上的氧化膜或氧化膜与涂层成分的反应产物。初步探讨了涂料的防护原理,指出涂层不能避免钢样氧化,而轻微氧化形成的氧化膜能与涂层成分反应形成复杂的氧化物,从而达到较好的防护效果。 相似文献
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《Journal of the European Ceramic Society》2020,40(7):2667-2673
Yb2SiO5 (ytterbium monosilicate) top coatings and Si bond coat layer were deposited by air plasma spray method as a protection layer on SiC substrates for environmental barrier coatings (EBCs) application. The Yb2SiO5-coated specimens were subjected to isothermal heat treatment at 1400 °C on air for 0, 1, 10, and 50 h. The Yb2SiO5 phase of the top coat layer reacted with Si from the bonding layer and O2 from atmosphere formed to the Yb2Si2O7 phase upon heat treatment at 1400 °C. The oxygen penetrated into the cracks to form SiO2 phase of thermally grown oxide (TGO) in the bond coat and the interface of specimens during heat treatment. Horizontal cracks were also observed, due to a mismatch of the coefficient of thermal expansion (CTE) between the top coat and bond coat. The isothermal heat treatment improves the hardness and elastic modulus of Yb2SiO5 coatings; however, these properties in the Si bond coat were a little bit decreased. 相似文献
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To study the effect of WC particles on corrosion behaviour of chromium coating steel samples were plated in Cr(VI) baths with various concentrations of WC. XPS, EPM and XRD were used to study the chemical composition, morphology and texture of the coatings. The corrosion behaviour was studied at different exposure times in solution containing 0.01 mol L–1 H2SO4 + 0.5 mol L–1 Na2SO4 using cyclic voltammetry and impedance spectroscopy. Cyclic polarization measurements suggest that WC particles slow down the processes of passive film dissolution and penetration of aggressive ions to the substrate. Electrochemical impedance spectroscopy (EIS) was used to reveal the details of the corrosion process at the solution/electrode interface. The simulation of EIS data with a proposed equivalent circuit model made it possible to obtain quantitative valuation of the Y0 (Qc), Y0 (Qs) and Rpore parameters, reflecting corrosion behaviour of samples at the solution/electrode interface. Samples plated in a Cr(VI) bath with WC provided better resistance to corrosion than those plated in a bath without WC. Analysis of the data obtained suggests that WC particles enhance corrosion resistance due to the microstructural features of the coatings. 相似文献
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以碳化硅(w(SiC)=99%,d50=5μm)、炭黑(w(C)=99.8%,d50=0.38μm)和单质硅(w(Si)=98.6%)为原料,无水乙醇(w(乙醇)=99.6%)、热塑性酚醛树脂(0.074μm、工业级)为结合剂,乌洛脱品为固化剂,以50 MPa的单向压力,分别将采用干混工艺、湿混工艺混合、干燥后的物料压制成型为50 mm×5 mm的生坯,在N2保护下经800℃焙烧、炭化处理,有机物热降解后得到陶瓷素坯。研究了酚醛树脂在不同加入量(其质量分数分别为4%、8%、10%、12%、16%)及混练工艺(干混、湿混)对反应烧结碳化硅素坯强度和烧结体显微结构的影响,并采用SEM和光学显微镜分析了试样的显微结构和断面形貌。结果表明:当酚醛树脂加入量为12%时,采用湿混工艺可以制备出具有良好可浸渗性且抗折强度高达45 MPa的素坯,完全可以满足复杂异型件在烧成以前进行机械加工的要求,烧结体的抗折强度最高可达455 MPa。与干混工艺相比,用湿混工艺制成烧结体的显微结构更加均匀,晶粒更加细小,裂纹扩展更加曲折。 相似文献
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Effect of silicon carbide additive on microstructure and properties of porcelain ceramics 总被引:1,自引:0,他引:1
Porcelain green bodies with various silicon carbide contents (0-3 wt.%) were prepared from a porcelain tile powder as a major raw material and SiC particle as an additive, and were sintered at 1000-1240 °C. The samples were systematically characterized by the X-ray diffraction (XRD), scanning electron microscope (SEM) and metallurgical microscope. Effects of the SiC content and sintering temperature on the pore size, SiC particle size and sintered density were investigated in detail, and the correlative mechanism was also discussed. The SiC particle size decreased and the pore size augmented with increasing the sintering temperature. The sintered density decreased and the pore size enlarged with increasing the SiC content. The experimental results indicate that a small amount of SiC can cause porcelain ceramics to foam during sintering, and a foaming origin of the polishing porcelain waste during sintering could be attributed to the oxidation reaction of SiC particles under high temperature and alkaline molten salt conditions. 相似文献
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《Journal of the European Ceramic Society》2017,37(3):891-897
Dense silicon carbide ceramics using chemical treated powder by DCC via dispersant reaction method and liquid phase sintering was reported. Ammonium peroxydisulfate ((NH4)2S2O8) and ammonium carbonate ((NH4)2CO3) were used as acid and base solutions to treat the silicon carbide powder, respectively. Influence of silicon carbide powder with chemical treatment on the preparation of silicon carbide suspension was studied. It was indicated that 50 vol% and 52 vol% silicon carbide suspensions with viscosities of 0.71 Pa s and 0.80 Pa s could be prepared using acid and base treated powders. Influence of silicon carbide powder with chemical treatment on the coagulation process and properties of green bodies and sintered ceramics were studied. It was indicated that silicon carbide green bodies with compressive strength of 1.13 MPa could be prepared using base treated powder. Dense silicon carbide ceramics with relative density above 99.3% and flexural strength of 697 ± 30 MPa had been prepared by DCC via dispersant reaction and liquid phase sintering using Al2O3 and Y2O3 as additives at 1950 °C for 2 h. 相似文献
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《Journal of the European Ceramic Society》2020,40(6):2253-2259
High temperature compressive creep tests have been performed at 1650−1750 °C under applied stresses of 50−150 MPa on sintered boron carbide samples exhibiting high relative density and a mean grain size of 0.5 μm. The creep behaviour of two types of materials, sintered by spark plasma sintering from both raw and heat-treated powders, are characterized. For both materials, the identification of creep parameters (i.e. apparent activation energy and stress exponent values) coupled with TEM structural observations suggest a power law creep regime controlled by dislocation glide, which is limited by the presence of twins. However, the TP material exhibits lower stationary strain rates. This improved creep resistance seems to be directly correlated to the stoichiometry modification of the carbide induced by the powder pre-heat treatment, i.e. increase of structural carbon content and slight decrease of oxygen amount. 相似文献
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氢氧化铬是含铬二次资源中铬的重要存在形式,也是含六价铬污染物还原时的主要产物,其氧化过程的研究对铬资源的提取和铬污染的控制具有重要意义。以亚硫酸钠还原重铬酸钠制备的氢氧化铬为研究对象,实验考察了氧化温度(室温~200 ℃)、氧化时间(0~168 h)、添加剂种类(碳酸钠、硫酸钠)等因素对氢氧化铬氧化的影响,并进行了氧化方程选取和动力学拟合计算。结果表明,温度越高两种氢氧化铬样品氧化反应越充分、氧化限度越大。在无添加剂条件下,200 ℃时新制、陈化氢氧化铬的氧化速率K值分别是80 ℃时的617、4 375倍;添加剂的加入会促进其氧化反应,140 ℃条件下,新制氢氧化铬添加碳酸钠、硫酸钠为n(Na)∶n(Cr)=0.2时的氧化速率K值分别是无添加时的10、4倍;新制氢氧化铬较陈化氢氧化铬更易氧化,氧化速率K值为陈化氢氧化铬样品的1.4~1.9倍,可能与其所含结合水较多有关。 相似文献
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Estíbaliz Sánchez-GonzálezPedro Miranda Fernando GuiberteauAntonia Pajares 《Journal of the European Ceramic Society》2011,31(6):1131-1139
The effect of the microstructure on the mechanical properties of pressureless, liquid-phase-sintered (LPS) α-SiC ceramics above room-temperature was studied. LPS-SiC ceramics were fabricated with different microstructural features (grain size and morphology, and content of the intergranular phase), and their mechanical behaviour under contact stresses was evaluated by high temperature Hertzian testing (HTHT) from room temperature up to the creep temperature (1000 °C). The amount of intergranular phase was found to control the elasto-plastic properties of LPS-SiC at intermediate temperatures. Grain size and morphology had a significant influence only on toughness, since the crack bridging mechanism was enhanced by elongated grains, the more so the larger their size. Implications of these results for the design and fabrication of LPS-SiC ceramics with tailored contact-mechanical properties are discussed. 相似文献
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采用了热失重分析仪(TGA)、傅里叶变换红外光谱(FTIR),扫描电子显微镜(SEM),广角X射线衍射(WAXD)等手段研究热处理对含杂环的共聚芳香族聚酰胺纤维结构与性能的影响。结果表明:热处理条件为氮气气氛,温度420℃,时间4 min,拉伸倍数为1;经过热处理后杂环芳纶的化学结构没有明显的变化,纤维结晶度由11.2%提高到51.6%,纤维的取向度显著提高,纤维的表面更加光滑致密;纤维的热稳定性无明显变化,纤维的线密度有略微变小,断裂强度为23.8 cN/dtex,弹性模量为1 041.43 cN/dtex。 相似文献
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Zhidan Zhou Yongxiong Chen Baolong Shen Dashu Guan 《Journal of Adhesion Science and Technology》2019,33(5):493-510
Herein, heat transfer from the coating to the substrate during the thermal spraying process is simplified as one-dimensional heat conduction and a formula to express the temperature distribution in the substrate is provided. To achieve this, the spray process was divided into two stages, namely deposition (coating sprayed onto the substrate) and post-deposition (cooling of coating and substrate to atmospheric temperature). The coating was achieved through a layer-by-layer deposition method. Residual stresses in the system (including both the coating and substrate) following deposition of each layer were calculated, as well as those induced by post-deposition. Finally, the proposed formulae were implemented in a real-case example to illustrate the effect of heat transfer with regards to torch velocity on residual stresses. The simulative results were shown to have a better agreement with experimental results at low rather than at high torch velocities. The residual stresses in the coating surface decreased with the increase in heat transfer time. When the heat transfer time exceeded a certain value, a sharp decline in residual stresses was observed. 相似文献
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采用超音速火焰喷涂(HVOF)工艺在35钢基体上制备了WC-10Ni涂层和WC-12Co涂层,研究了镍、钴这两种粘结剂对WC涂层的显微硬度、摩擦系数和抗磨粒磨损性能的影响,采用扫描电子显微镜观察涂层磨损前后的表面形貌,探讨了WC涂层的磨粒磨损机理。结果表明,以HVOF方法制备的2种WC涂层均有较高的显微硬度,WC-10Ni涂层和WC-12Co涂层与SiC砂纸摩擦副之间的干摩擦系数相差不大。2种涂层在低载荷下均有较好的抗磨粒磨损性能,但在较高载荷下WC-12Co涂层的抗磨性明显优于WC-10Ni涂层。2种涂层的磨粒磨损形式主要为均匀磨耗磨损,磨损机理以微切削和微剥落为主。WC-12Co涂层的磨损表面损伤较轻微,综合性能优于WC-10Ni涂层。 相似文献