Vanadium carbide coating growth on die steel substrate in borax salt bath

Vanadium pentoxide, borax, boron carbide and sodium fluoride were used to grow vanadium carbide coating on die steel(Cr₁₂, Cr₁₂MoV) surface at 950 °C by TD process, which extended the life period of Cr₁₂ and Cr₁₂MoV as punching die. Kinetics of vanadium carbide coating growth was brought forward and verified by comparison of the mathematical model with the experimental results. The thickness of coating was illustrated by SEM. The chemical constituent of coating and remnants were tested by XRD. To increase the thickness, rare earths (FeSiRe₂₃) were added to the borax salt bath. The electronic probe microanalysis (EPMA) revealed that the addition of rare earths could decrease carbon concentration in the coating and increase the depth of vanadium carbide coating.     

Composition variation of borax salt during the process of vanadizing by thermal diffusion

Vanadium pentoxide,borax,boron carbide and sodium fluoride were used to grow vanadium carbide coating on surface of Cr12 steel at 950 ℃ by TD process.The coating of vanadium carbide(VC)extended the serve-life period of Cr12 steel as punching die.Kinetics of vanadium carbide coating growth was brought forward and verified by comparison of the mathematical model with the experimental results.The thickness of coating was illustrated by SEM.The chemical constituent of coating and remnants were tested by X-ray diffraction(XRD)and X-ray energy dispersive spectroscopy(EDS).To increase the thickness,rare earth silicon powder(FeSiRe23)was added to the borax salt bath.The analysis of XRD revealed that FeSiRe23 increased the depth of vanadium car-bide coating as reducing agent and catalysis.     

Mierostrueture and Properties of Coating from Cemented Carbide on Surface of H13 Steel

The microstructures and properties of coating from cemented carbide on the substrate of H 13 by vacuum powder sintering were studied. The effect of sintering temperature on the microstructures of coating was discussed. The interface characteristics between coating and H 13 steel substrate, microhardness distribution and wear resistance in the coating were analyzed. The coating from cemented carbide with thickness of 1-3 mm by vacuum powder sintering at temperature ranging from 1280℃to 1300 ℃ was obtained. The experimental results indicated that the coating with microhardness of HV 1600 favorable to wear resistance is strongly bonded with the H 13 steel substrate by mutual diffusion and penetration of Fe,Cr, Mo,V in substrate towards the coating and W, Co,Ni in coating towards the substrate.     

电镀法制备Ni-W合金镀层的耐盐雾腐蚀性能

利用电镀法在N80钢表面制备了Ni-W合金镀层,用SEM、EDS分析了镀层表面与界面形貌以及化学元素的分布,通过XRD测试了镀层物相的组成。在5% NaCl溶液中测试了镀层盐雾腐蚀能力,分析了Ni-W镀层抗盐雾腐蚀机理。试验结果表明,镀层厚度约40m,主相为Ni-W,Ni和W以金属形式存在于镀层中;经过高温热处理后,镀层与基体发生了化学元素扩散现象,形成冶金结合;盐雾腐蚀后镀层表面腐蚀物为Fe的氧化物和氯化物,基体无腐蚀现象发生。     

Improved oxidation resistance of chemical vapor reaction SiC coating modified with silica for carbon/carbon composites

To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by chemical vapor reaction (CVR): a simple and cheap technique to prepare the SiC coating via siliconizing the substrate that was exposed to the mixed vapor (Si and SiO2) at high temperatures (1 923?2 273 K). Then the as-prepared coating was processed by a dipping and drying procedure with tetraet...     

不锈钢基体室温熔盐电沉积铝

在AlC1₃-EMIC室温熔盐体系中,在201不锈钢基体上电沉积了铝镀层,并利用金相显微镜、能量色散谱和扫描电镜对镀层的成分、表面形貌及镀层与基体之间的结合情况进行了观察分析.结果表明,201不锈钢基体可以通过AlC1₃-EMIC室温熔盐电沉积的方法获得完整平滑且纯度较高的铝镀层.铝镀层晶粒尺寸随电流密度变化较为明显,随电流密度的增大,晶粒尺寸变小,镀层更加致密化.在电沉积前,通过阳极活化对不锈钢基体进行预处理,可以使铝镀层和不锈钢基体的结合得到显著的提高;通过对电沉积后试样进行热处理,可以提高铝镀层和基体之间的结合力.     

基于辐射传输方程的稀土辐射器厚度优化分析

对以碳化硅为基底、氧化镱为表面涂层的选择性辐射器进行优化分析,基于热辐射传输方程和能量平衡方程建立数学模型,研究带内、带外光谱发射率与涂层厚度的变化关系.结果表明:涂层内外温差对发射率有削弱作用,而且涂层厚度越大这种削弱作用越明显.以0.98μm为典型波长的带内辐射,在涂层厚度为0.25mm时发射率有最大值;以1.8μm为典型波长的带外辐射,发射率随涂层厚度增加而单调增大.依据高性能辐射器应同时具备较高的带内发射率和较低的带外发射率的原则,综合分析得出稀土辐射器氧化镱涂层的最优厚度为0.25mm.     

TiC涂层梯度硬质合金残余热应力分析

采用有限元方法分析有无梯度2种TiC涂层硬质合金的残余热应力,研究了残余应力随涂层及梯度层厚度的变化。结果表明:增加梯度层后,涂层内残余热应力的减小超过10%,合金中残余应力减小30%以上,表面残余应力也明显下降;随着涂层厚度的增加,涂层内拉应力大幅减小,剪切应力与等效应力略微增加,涂层梯度硬质合金的等效应力呈下降趋势;随着梯度层厚度的增加,涂层内残余应力减小,当梯度层厚度较大时,残余应力不再改变。因此,选择合适的涂层和梯度层厚度,涂层厚度一般为5～8μm,梯度层厚度控制在20μm左右,可以有效缓和残余应力,提高材料的结合强度。     

Electrochemical Reaction Processes of Niobium Ions in FLINAK melt

ThecathodicProcessmechanismofniobiumreductionfromchloride-fluorideandfiuoridemeltshasbeenstudiedindetail[l-],batthereseemsstilltobesomedismpemelltconcerningthereductionmechanism.Essentially,threehoesofmodelshaVebeenPutforwardtoexplaintheelectrochemic...     

Corrosion resistance of plasma sprayed NiCrAl+(ZrO2+Y2O3) thermal barrier coating on 18-8 steel surface

The corrosion resistance of NiCrAl+(ZrO₂+Y₂O₃) thermal barrier coating, formed with the plasma spraying technique, on the 18 - 8 steel surface was investigated. The phase structure and morphology of the coating were analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical corrosion behavior of the coating in 1.0 mol/L H₂SO₄ solution was studied by using electrochemical measurement methods. The results show that the gradient plasma spraying coating is composed of the NiCrAlY coating and the (ZrO₂+Y₂O₃) top coating, and the coating thickness is 360 μm. The microhardness of coating reaches 1 100 HV. The corrosion resistance of the plasma sprayed coating of the 18 - 8 steel surface is about 5 times as great as that of the original pattern. The corrosion resistance of the coating is enhanced notably. Foundation item: Project (5040202140) supported by Scientific Research Common Program of Beijing Municipal Commission of Education     

Siliconizing formation mechanism and its property by slurry pack cementation on electro-deposited nickel layer into copper matrix

Silicide coating was prepared on electro-deposited nickel layer by the slurry pack cementation process on copper matrix at 1173 K for 12 h using SiO₂ as Si source, pure Al powder as reducer, a dual activator of NaF+NH₄Cl and albumen (egg white) as cohesive agent. Microstructure, properties and siliconizing mechanism of silicide coating were discussed. The experimental results show that the silicide coating with 220 μm thickness is mainly composed of a Ni₂Si phase and a small amount of Ni₃₁Si₁₂ phase. Its mean microhardness (HV 790) is ten times than that of copper substrate (HV 70). The coefficient of friction decreases from 0.8 of pure copper to about 0.3 of the siliconzed sample. SiF₂, SiCl₂ and SiCl₃ are responsible for the transportation and deposition of Si during the slurry pack cementation process.     

Examination of carbon diffusion in niobium clad steel composite

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Properties of plasma sprayed NiCrAlY+(ZrO2+Y2O3) coating on refractory steel surface

NiCrAlY+(ZrO₂+Y₂O₃) thermal barrier coating was prepared on the surface of refractory steel 1Cr18Ni9Ti with plasma spraying technique. The phases and microstructure of the thermal barrier coating were determined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the bonding between thermal barrier coating and substrate is sound. The surface hardness of 1Cr18Ni9Ti reaches up to 1 000 HV, but that of substrate is only 300 HV. The patterns sprayed with CoNiCrAlY+(ZrO₂+Y₂O₃) ceramic coating have a good heat insulation effect at 800 °C for heat insulation temperature difference reaches 54 °C, which increases the operating temperature and service life of refractory steel. Foundation item: Project (5040202140) supported by Scientific Research Common Program of Beijing Municipal Commission of Education     

Preparation and performance evaluation of Er2O3 coating-type selective emitter

An Er2O3coating-type selective emitter for themophotovoltaic application was prepared by plasma spray technology.The test results show that plasma spray technology could be used to prepare the Er2O3coating-type selective emitter with good stability at 1400°C.Based on the measurements of the high temperature normal spectral emissivity and the spectral hemispherical emissivity of the samples at room temperature,the influence of the coating thickness was discussed,and the selective emission performance of the sample was evaluated using radiative efficiency as the criterion.The results demonstrate that the emission of substrate could not be neglected unless the coating thickness would be larger than the penetration depth,which is around100μm.The selective emission peak of the Er2O3coating occurs at 1550 nm,matching well with the GaSb cells.However,the radiative efficiency is not larger than that of the SiC emitter,because the non-convertible emission of 1.725–5 m accounts for a large proportion of the total radiation power,especially at high temperature.Effective suppression of this band emission is essential to the improvement of the radiation efficiency of the emitter.     

Microstructure and thermal properties of SiCp/Cu composites with Mo coating on SiC particles

SiCp/Cu composites with a compact microstructure were successfully fabricated by vacuum hot-pressing method. In order to suppress the detrimental interfacial reactions and ameliorate the interfacial bonding between copper and silicon carbide, molybdenum coating was deposited on the surface of silicon carbide by magnetron sputtering method and crystallized heat-treatment. The effects of the interfacial design on the thermo-physical properties of Si Cp/Cu composites were studied in detail. Thermal conductivity and expansion test results showed that silicon carbide particles coated with uniform and compact molybdenum coating have improved the comprehensive thermal properties of the Si Cp/Cu composites. Furthermore, the adhesion of the interface between silicon carbide and copper was significantly strengthened after molybdenum coating. Si Cp/Cu composites with a maximum thermal conductivity of 274.056 W/(m·K) and a coefficient of thermal expansion of 9 ppm/K were successfully prepared when the volume of silicon carbide was about 50%, and these Si Cp/Cu composites have potential applications for the electronic packageing of the high integration electronic devices.     

42CrMo钢液相等离子碳氮共渗工艺研究

本文以乙醇胺、氯化钾、氯化铵的水溶液为电解液,用液相等离子电解技术对42CrMo钢进行碳氮共渗工艺进行研究。通过金相显微镜、扫描电镜（SEM）、电子能谱（EDS）、对处理试样表面形貌和渗层进行观察和分析,并对渗层硬度通过显微硬度计进行测试。结果表明：利用液相等离子电解技术可以实现42CrMo钢的碳氮共渗,渗层厚度可以达到60μm,渗层硬度可以达到537 HV,基本达到基体硬度的2倍。     

碳钢膏剂渗硼后的热处理工艺及性能研究

利用正交试验法,获得了较佳的碳钢膏剂渗硼工艺及渗剂配方,分别研究了45钢及T10钢膏剂渗硼后不同的热处理工艺对渗硼层及基体组织和性能的影响。实验结果表明:45钢在渗硼后渗层显微硬度均在1 130 HV以上,厚度皆在110μm以上;T10钢渗硼后的渗层厚度均在60μm以上,渗层的显微硬度均在1 360 HV以上;热处理对渗硼层的硬度及厚度没有影响,但对基体组织及性能有明显影响;渗硼后采用淬火及低温回火工艺,可使基体获得回火马氏体组织,从而提高了基体的硬度,减小了基体与渗硼层的硬度差,也提高了基体对渗硼层的支撑作用。     

Microstructure and wear resistance of in situ NbC particles reinforced Ni-based alloy composite coating by laser cladding

The in situ synthesized NbC particles reinforced Ni-based alloy composite coating was produced by laser cladding a precursor mixture of Ni-based alloy powder,graphite and niobium powders on a steel substrate.The microstructure,phase composition and wear property of the composite coating were investigated by means of scanning electron microscopy(SEM),X-ray diffraction(XRD)and dry sliding wear test.The experiment results show that the composite coating is homogeneous and free from cracks,and about 0.8 mm thick.The microstructure of the composite coating is mainly composed of NbC particles,CrB type chromium borides,γ-Ni primary dendrites,and interdendritic eutectics.CrB phases often nucleate and grow on the surface of NbC particles or in their close vicinity.NbC particles are formed via in situ reaction between niobium and graphite in the molten pool during the laser cladding process and they are commonly precipitated in three kinds of morphologies,such as quadrangle,cluster,and flower-like shape.Compared with the pure Ni-based alloy coating,the microhardness of the composite coating is increased about 38%,giving a high average hardness of HV0.21000,and the wear rate of the composite coating is decreased by about 32%,respectively.These are attributed to the presence of in situ synthesized NbC particles and their well distribution in the coating.     

Influence of a TiAlN coating on the mechanical properties of a heat resistant steel at room temperature and 650 °C

A TiAlN coating was deposited on a heat resistant steel X12CrMoWVNbN10-1-1 by vacuum arc ion plating. The tensile and fatigue properties of the coated steel were investigated at room temperature (RT) and 650 °C. The results reveal that the TiAlN coating is compact, on which a small number of large particle and pits are present. The Ti/Al atomic ratio in the coating is about 0.94. The average hardness of the coating is 1 868 HV0.1 and the interface bonding force between TiAlN coating and the substrate is about 31 N. The elastic modulus and the strength of the steel are improved by the deposition of TiAlN coating. The influence of the TiAlN coating on the tensile properties of the steel can be ignored at both RT and 650 °C. Moreover, there is no obvious decrease of the fatigue limit of substrate when the steel is coated by the coating at the investigated temperature.     

Ti过渡层厚度对Ti—TiN薄膜结合强度的影响

薄膜脱落的主要原因之一是受薄膜与基体上的界面应力影响,TiN薄膜和钢基体由于其力学性能差异较大,在界面上有很大的应力集中,在钢基体上沉积Ti过渡层能减小其界面应力。研究Ti过渡层厚度对膜基体系结合强度的影响．并借助有限元方法对不同过渡层厚度的膜基体系的界面应力进行分析,研究表明,适当厚度的过渡层能提高Ti-TiN膜层的结合强度。