泡沫Ni-32Cr合金的结构及其性能研究

以聚氨酯泡沫树脂为基体,采用浆料涂覆、电沉积、热解和合金化等技术制备出网状结构的高孔率泡沫Ni-32Cr合金.对该泡沫合金的形貌结构、成分分布和使用性能进行了分析研究.实验结果表明:该泡沫合金骨架平整,成分均匀,相对密度为6.4%,骨架的室温显微硬度HV为168,压缩强度约5MPa,且800℃时氧化1h,其增重率小于2×10-3.     

Corrosion of nickel-chromium alloys, stainless steel and niobium at supercritical water oxidation conditions

Results of immersion tests of UNS N06625 (alloy 625), UNS S31609 (alloy 316 L), Ni-20Cr alloy and Nb coupons exposed to oxygenated ammoniacal sulphate solution at supercritical water oxidation (SCWO) conditions are presented. The corrosion behavior of the alloy 316 L (UNS S31603) SCWO reactor tubing is also presented under the same conditions. Immersion coupons corroded at a rate not exceeding 40 mm yr⁻¹ while the reactor tube itself corroded at a rate of between 160-1500 mm yr⁻¹, depending on which length of the reactor is considered to have corroded. Morphological and chemical analysis of the oxides present on the coupon samples suggest that iron oxides, which had initially precipitated on the corroding alloy 316 tube surface, were removed by heat flux-driven fluid mechanical action and transported through the reactor where they deposited on the coupons. Niobium was resistant to corrosion at the tested conditions.     

Ni-Cr合金真空钎焊金刚石的热损伤分析

钎焊金刚石工具具有高的出露和连接强度,但金刚石磨料在钎焊过程中所受的热损伤对其寿命影响较大,因此文中对钎焊金刚石的热损伤作了分析.采用Ni-Cr合金对金刚石进行钎焊试验,利用SEM,EDS对金刚石的表面形貌进行观察分析,采用拉曼光谱仪对金刚石表面进行石墨化分析及热应力分析.结果表明,经Ni-Cr合金钎焊后金刚石表面有较多的碳化物(Cr3C2,Cr7C3)生成,同时发现金刚石表面有少量石墨化和化学侵蚀,其顶部的拉应力大约为110MPa,底部的压应力大约为520MPa.     

Experiments Design for Hardness Optimization of the Ni-Cr Alloy Electrodeposited by Pulse Plating

The hardness of the Ni-Cr alloy which is electrodeposited in chloride solution,is optimized by design of experiment method(central composite design).Various parameters were evaluated in order to find significant factors in this process.Frequency,duty cycle,current density and temperature were selected as efective factors.Analyses of variance(ANOVA)were performed on the results of the designed experiments.The best model which can predict the hardness of the Ni-Cr alloy electrodeposits was found whereas the frequency and quadratic behaviour of the current density were the most significant model terms.Serious interaction of the current density with frequency and duty cycle also were found in this model.Finally the optimum conditions of the factors for obtaining the maximum hardness of the Ni-Cr alloy were found.Ni-Cr alloy with hardness828 HV(electrodeposited with frequency 63 Hz,current density 1800 A/m2,duty cycle 75%and temperature31℃ bath)were assessed as the optimum deposit.The deposit under the optimum condition was investigated by scanning electron microscopy(SEM),EDX analysis,polarization method and microhardness.     

Ni-Cr合金真空钎焊金刚石的表面石墨化

以Ni-Cr合金为钎料采用真空钎焊的方法制备了金刚石钎焊试样.运用扫描电镜(SEM)、X射线能谱仪(EDS)及显微激光拉曼光谱仪对钎焊金刚石表面石墨化的形貌、石墨化程度进行了综合分析.结果表明,在Ni-Cr合金钎料真空钎焊金刚石的过程中,金刚石的表面生成了石墨,其厚度约为10μm;而钎焊过程中,金刚石表面C原子结构的破坏、解体以及降温过程中C原子的析出和再结晶是导致金刚石石墨化的原因;钎焊时在金刚石表面先生成石墨后生成碳化物.     

镀制方式对高衰减镍铬合金膜中性度的影响

对比了用不同镀制工艺方式镀制的Ni80Cr20膜中性密度滤光片的中性度特性,溅射工艺镀制的密度片中性度值3.7%,远好于电子枪蒸发和电阻蒸发镀制结果(15%)。采用相平衡理论,模拟计算了的热蒸发镀制的镍铬合金膜的蒸发速率,铬相比镍含量偏高2.8倍,导致了膜层中合金含量相对膜料出现较大差异,导致中性密度滤光片光谱中性度的下降。使用蔡司SUPRA35扫描电镜和牛津EDS能谱仪分别测试了溅射工艺和热蒸发工艺镀制的密度滤光片的镍铬含量,测试结果与模拟分析结论基本一致。     

Synergistic effect of metal components of the low-loaded Pt-Ni-Cr/C catalyst in the bicyclohexyl dehydrogenation reaction

The problem of hydrogen storage in liquid organic hydrogen carriers is not only the choice of an appropriate organic substrate, but the development of a selective and active catalyst containing as low as possible noble metals. A synergistic effect of increasing conversion and selectivity in bicyclohexyl dehydrogenation to biphenyl on trimetallic Pt-Ni-Cr/C catalysts with an extremely low Pt loading (0.1 wt %), compared with bimetallic Ni-Cr/C and Pt/Ni/C systems, due to the supporting of platinum on nickel-chromium nanoparticles was established for the first time. The TOF values (mmol (H₂)/g_Pt min) for hydrogen evolution under conditions of the reaction of bicyclohexyl dehydrogenation (320 °C, 0.1 MPa) on Pt supported onto a Ni-Cr/С composite exceed by two orders of magnitude the values found for the two-component catalysts. The maximum amount of the evolved hydrogen correlates to the selectivity of the complete dehydrogenation of bicyclohexyl into biphenyl on the Pt-Ni-Cr/C catalyst. The formation of a Ni-Cr solid substitution solution in a Ni-Cr composite deposited on a carbon carrier is shown by magnetometry, XRD, and TEM methods.     

焦炉用铠装热电偶失效原因分析

国内某钢铁厂焦炉测温用铠装热电偶,安装后使用5天便发生了失效故障,无法显示温度读数。为探究其热电偶失效原因,对其铠装热电偶先后进行了低倍下的宏观形貌观察、扫描断口分析、显微组织分析和电子探针成分分析等。结果表明:该热电偶失效的原因是镍铬端发生了择优氧化。改进措施及建议:使用时合理选择适合型号的热电偶,排除K型热电偶在加工时表面的氧化皮以及还原性介质的介入和采用较小的长径比。     

Effect of Rare Earth Elements on Thermal Fatigue of High Ni－Cr Alloy Cast Iron

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铝合金表面电火花堆焊的NiCr合金层

研究了铝合金表面电火花堆焊的NiCr合金层,观察与分析不同保护气氛下的焊点形貌、截面组织形态及层间组织特征。认为堆焊点是由基体熔坑与电极不规则散落熔滴组成的,堆焊层表面呈粗糙不规则平面;堆焊层组织非常细密,须状晶呈平行分布;在氩气保护下,焊点周围有“阴极雾化”现象;堆焊层与基体间存在元素相互扩散。