304不锈钢硼化层的微观组织结构分析

以304不锈钢为基材,利用自制固体渗剂在不锈钢表面成功制备了硼化层,厚度可达50μm,结合强度为33.5MPa。利用X射线衍射仪和透射电镜对硼化层的相结构和微观组织结构进行分析,并利用电子探针对硼化层的截面形貌进行分析。结果表明,硼化层主要有FeB和Fe2B相组成,Fe2B晶粒细小,晶界平直;夹在Fe2B晶粒之间的齿间组织粗糙不平,是基体合金元素和B元素结合生成的硼化物,这些硼化物紧密的附着在Fe2B晶粒上。这些组织有利于提高硼化层与基体的结合强度。

钢的复合硼化层金相学研究

分析并系统研究了合金元素对复合硼化层宏观组织、深度、相成份及显微硬度的影响。

热处理对钢的复合硼化层相成分及显微硬度的影响

分析研究了热处理工艺对08钢复合硼化层相成分及显微硬度的影响

硼化球墨铸铁中硼化物层的断裂韧性

本文研究了硼化球墨铸铁中硼化物的断裂韧性。渗硼是在硼砂、硼酸和硅化铁组成的盐浴中进行的，其热处理工艺是在常压下，加热温度在850—950℃之间，时间为2—8小时。通过X—my衍射、扫描电子显微镜以及光学显微镜等方法验证了球墨铸铁中形成的硼化物(如FeB，Fe2B)。试验结果表明，渗硼时间越长，所形成的硼化物层也越厚，硼化物层截面的光学显微镜观察表明硼化物呈枝晶状。硼化物层显微硬度和断裂韧性可用压痕法来测定。球墨铸铁中形成硼化层的维氏显微硬度在1160-2140HV0.1之间，其断裂韧性在2．19—4．47MPa√m之间，硼化层的硬度和断裂韧性与渗硼时间及温度有关。

Preparation and oxidation resistance of B_2O_3-coated boron-modified carbon foams

To improve the oxidation resistance of boron-modified carbon foams, the B2O3 coating was prepared on boron-modified carbon foams by low-cost slurry method. The microstructures and phase compositions of the coated carbon foams were characterized by scanning electron microscopy and X-ray diffraction, respectively. Oxidation resistances of uncoated and coated boron-modified carbon foams were investigated at 873 K in air. The results showed that as-received B2O3 coating could protect boron-modified carbon foams from oxidation at 873 K. B2O3-coated carbon foam doped with 7% B2O3 （mass fraction） （BO-7） had better oxidation resistance, exhibiting mass loss of 17.40% after oxidation at 873 K for 120 min. The melting glass layer formed on the surface of BO-7 could prevent oxygen from diffusing into boron-modified carbon foams substrate during oxidation to some extent.

Formability of aluminum-silicon coated boron steel in hot stamping process

Flow behavior of the Al-Si coated boron steel was investigated with Gleeble-3500,in comparison with the uncoated one.Effect of deformation conditions on the coating integrity was characterized by optical microscopy.Facture surfaces of the coated steels were inspected under SEM.Experimental results indicate that the ultimate tensile strength and ductility of the Al-Si coated boron steel are lower than those of the uncoated steel under test conditions.Extensive cracks occur in the coating after tensile tests;the width and density of cracks are sensitive to the deformation temperatures and strain rates.The bare substrate exposed between the separate coating segments is oxidized.Appearance of the oxide degrades the Al-Si coating adhesion.Remarkable difference between formability of the coating layer and the substrate is confirmed.The formability of the Al-Si coating could be optimized by controlling the phase transformation of the ductile Fe-rich intermetallic compounds within it during the austenization.

ZrB2–SiC多层陶瓷的抗氧化性

用传统陶瓷的流延工艺制备ZrB2–SiC多层陶瓷。用Archimedes法测定ZrB2–SiC多层陶瓷的相对密度。用扫描电子显微镜观察其显微结构,并进行循环抗氧化性能评价。结果表明:ZrB2–SiC多层陶瓷在1 950℃烧结的致密度达到99.7%,材料的抗氧化过程主要可分为两个阶段:第一阶段低熔点相的挥发,出现质量损失;第二阶段氧化层的形成,降低进一步氧化速率。抗氧化性能较ZrB2–SiC复相陶瓷有很大提高。

Nanomechanical properties and fracture toughness of hard ceramic layer produced by gas boriding of Inconel 600 alloy

Gas-boriding in N2-H2-BCl3 atmosphere resulted in the formation of a thick layer on Inconel 600 alloy.The microstructure of layer produced at 920℃for 2 h consisted of a mixture of chromium borides and nickel borides.The objective of investigations was to determine the influence of the chemical and phase compositions of borided layer on its mechanical properties.The nanoindentation was carried out using Berkovich diamond tip under a load of 50 m N.The gas-borided layer was characterized by high indentation hardness HIT from 1542.6 HV to 2228.7 HV and high elastic modulus EIT from 226.9 to 296.4 GPa.It was found that the mixture with higher percentage of chromium borides was the reason for the increase in HIT and EIT values.The fracture toughness(KC)was measured using Vickers microindentation technique under a load of 0.98 N.The presence of high compressive stresses in normal direction to the top surface caused the strong anisotropy of the borided layer,in respect of fracture toughness.The high difference between the lowest(0.5763 MPa·m^1/2)and the highest(4.5794 MPa·m^1/2)fracture toughness was obtained.This situation was caused by the differences in chemical and phase compositions of tested areas,presence of porosity and residual stresses.Generally,the higher KC values were obtained in areas with lower chromium content.

Fabrication of TiN/cBN and TiC/diamond coated particles by titanium deposition process

Cubic boron nitride particles coated by titanium nitride (TiN/cBN) as well as diamond particles coated by titanium carbide (TiC/diamond) were prepared by Ti molten salt deposition followed by heat-treatment process. cBN or diamond particles were mixed separately with Ti powders and molten salts (KCl, NaCl and K2TiF6). The mixture was heated at 900 °C under argon atmosphere. The produced particles were heat-treated under hydrogen at 1000 °C. The morphologies and chemical compositions of the produced particles were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and focused ion beam (FIB). The results show that the cBN and the diamond particles are coated by nano-sized Ti layers. By heat-treatment of the Ti/cBN and TiC/diamond coated particles under hydrogen atmosphere, the deposited Ti layers were interacted by the in-situ transformation reaction with the surfaces of cBN and diamond particles and converted to titanium compounds (TiN and TiC), respectively.

Features of the Process of Self-Propagating High-Temperature Synthesis, a Structure and Strong Properties of Borides Iron Layers on the Carbon Steels, Generated Under a Powerful Electron Beam in Vacuum

Conditions of formation, structure and properties of boride iron layers on carbonaceous steels 3 and 45 at electron beam borating are investigated. New process to make layers of iron borides （Fe2B, FeB） using electron beam are reported. The microstructure and microhardness of boride layers are investigated and also are compared to layer properties obtained at solid phase borating. Formed layers were heterogeneous structure combining solid and weak components and resulting in to fragility reduction of boride layer.

Optimizing the nickel boride layer thickness in a spectroelectrochemical ATR-FTIR thin-film flow cell applied in glycerol oxidation

The influence of the drop-casted nickel boride catalyst loading on glassy carbon electrodes was investigated in a spectroelectrochemical ATR-FTIR thin-film flow cell applied in alkaline glycerol electrooxidation.The continuously operated radial flow cell consisted of a borehole electrode positioned 50μm above an internal reflection element enabling operando FTIR spectroscopy.It is identified as a suitable tool for facile and reproducible screening of electrocatalysts under well-defined conditions,additionally providing access to the selectivities in complex reaction networks such as glycerol oxidation.The fast product identification by ATR-IR spectroscopy was validated by the more time-consuming quantitative HPLC analysis of the pumped electrolyte.High degrees of glycerol conversion were achieved under the applied laminar flow conditions using 0.1 M glycerol and 1 M KOH in water and a flow rate of 5μL min^(–1).Conversion and selectivity were found to depend on the catalyst loading,which determined the catalyst layer thickness and roughness.The highest loading of 210μg cm^(–2)resulted in 73%conversion and a higher formate selectivity of almost 80%,which is ascribed to longer residence times in rougher films favoring readsorption and C–C bond scission.The lowest loading of 13μg cm^(–2)was sufficient to reach 63%conversion,a lower formate selectivity of 60%,and,correspondingly,higher selectivities of C_(2)species such as glycolate amounting to 8%.Thus,only low catalyst loadings resulting in very thin films in the fewμm thickness range are suitable for reliable catalyst screening.

Growth and low-energy electron microscopy characteri- zation of monolayer hexagonal boron nitride on epitaxial cobalt

Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-BN films are grown on heteroepitaxial Co using chemical vapor deposition （CVD） at low pressure. Our findings from LEEM studies include the growth of monolayer film having two, oppositely oriented, triangular BN domains commensurate with the Co lattice. The growth of h-BN appears to be self-limiting at a monolayer, with thicker domains only appearing in patches, presumably initiated between domain boundaries. Reflectivity measurements of the thicker h-BN films show oscillations resulting from the resonant electron transmission through quantized electronic states of the h-BN films, with the number of minima scaling up with the number of h-BN layers. First principles density functional theory （DFT） calculations show that the positions of oscillations are related to the electronic band structure of h-BN.