Thermal spray coating on conductor rolls in electroplating line

In electroplating lines,many conductor rolls are installed in electroplating bath.Typical electroplatings are tin plating(ETL) and zinc plating(EGL),and from required product qualities,a vertical cell for the former and a horizontal cell for the latter is often used.Generally,chrome plating or WC cermet thermal spray coating is applied to stainless steel conductor roll in ETL for prolonging service life by improvement of wear resistance and corrosion resistance.On the other hand,Hastelloy type alloy subs...     

Determination of thermal conductivity from specific heat and thermal diffusivity measurements of plasma-sprayed cermets

The thermal conductivities of three plasma-sprayed cermets have been determined over the temperature range 23–630°C from the measurement of the specific heat, thermal diffusivity, and density. These cermets are mixtures of Al and SiC prepared by plasma spray deposition and are being considered for various applications in magnetic confinement fusion devices. The samples consisted of three compositions: 61 vol% Al/39 vol% SiC, 74vol% Al/26vol% SiC, and 83 vol% Al/17 vol% SiC. The specific heat was determined by differential scanning calorimetry through the Al melt transition up to 720°C, while the thermal diffusivity was determined using the laser flash technique up to 630°C. The linear thermal expansion was measured and used to correct the diffusivity and density values. The thermal diffusivity showed a significant increase after thermal cycling due to a reduction in the intergrain contact resistance, increasing from 0.4 to 0.6 cm²·^–1 at 160°C. However, effective medium theory calculations indicated that the thermal conductivities of both the Al and the SiC were below the ideal defect-free limit even after high-temperature cycling. The specific heat measurements showed suppressed melting points in the plasmasprayed cermets. The 39 vol% SiC began a melt endotherm at 577°C, which peaked in the 640–650°C range depending on the sample thermal history. Chemical and X-ray diffraction analysis indicated the presence of free silicon in the cermet and in the SiC powder, which resulted in a eutectic Al/Si alloy.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

镍系聚丁二烯橡胶生产技术进展

介绍了国内外镍系聚丁二烯橡胶生产技术的特点、催化体系的改进、镍系聚丁二烯橡胶的高性能化,以及国内镍系聚丁二烯橡胶技术的研究进展。     

The alloying mechanisms of Re, Ru in the quaternary Ni-based superalloys interface: A first principles calculation

The site preference of Re, Ru on the γ/γ^′ interface and their influence on the partitioning behaviors of W, Mo in the γ and γ^′ phase have been investigated by DMol3 calculation. The transfer energy results show that both Re and Ru exhibit a weak Ni site preference. When Re substitutes Ni on the γ/γ^′ interface, it is found a reverse partitioning behavior of W, while the partitioning behavior of Mo was not affected. In contrast, Ru’s substitution for Ni on the interface does not affect the partitioning behaviors of W, Mo, which is in agreement with experimental results. In addition, the different interface strengthening mechanisms for Re and Ru are investigated by the electronic structure analysis of the Mulliken population, the impurity-induced charge redistribution and the partial density of states. Results show that the alloying strengthening effect of Re is mainly due to the direct bonding of Re and the host atoms. Whereas, the addition of Ru is effective for improving the phase stability of Ni-based superalloys.     

Double oxide film defects in Ni-based super-alloy castings

A new class of defects has been recently discovered, which are regarded as double oxide film defects. In this study, a number of Ni-based vacuum-cast test bars were investigated. The fractures in the broken test bars were observed by Scanning Electron Microscopy （SEM）. Energy Dispersive Spectroscopy （EDS）, as well as Wavelength Dispersive Spectroscopy （WDS） were used to characterize the chemical elements of the fracture＇s surface. Observation by SEM revealed the presence of inclusions identified as films that appeared to have initiated the growth of carbides. This study has added to the evidence that oxide film defects do exist in Ni-based super-alloy in certain vacuum casting conditions. It provides a reference for researchers＇ further study on the defects, and provides a possible direction for researchers to improve casting technology so as to remove these defects.     

Microstructure characteristics of Ni-based WC composite coatings by laser induction hybrid rapid cladding

To avoid low cladding rate and cracks of cladding layer, laser induction hybrid rapid cladding (LIHRC) has been put forward in the paper. The microstructure characteristics of Ni-based WC composite coatings at the different laser scanning speed were investigated. For low laser scanning speed, the growth of γ-nickel was characterized by coarse columnar dendrites and eutectics, blocky W₂C + Fe₃W₃C carbides, and bar-like (W, Cr, Ni)₂₃C₆ carbides were formed. With increasing laser scanning speed, the growth of γ-nickel presented the fine dendrites and eutectics, the only blocky mixed carbides were precipitated and identified as W₂C + FeW₃C + W₆C_2.54 carbides. With further increasing laser scanning speed, the growth of γ-nickel was characterized by cellular crystals and eutectics, the only blocky carbides were identified as W₂C + W₆C_2.54. Moreover, experimental results showed that the efficiency of LIHRC was increased much four times higher than that of laser cladding without preheating, ceramic–metal composite coatings detected were free of cracks and had a good metallurgical bonding with substrate.     

铸造WC/Ni基合金复合材料二体磨料磨损性能的研究

用真空热压液相烧结技术制备铸造WC／Ni基合金复合材料。研究了铸造WC的颗粒尺寸及体积分数对复合材料的二体磨料磨损性能的影响，并将它与高铬铸铁(Cr28)相比较。结果表明：随着铸造碳化钨颗粒尺寸和体积分数的增大，复合材料的耐磨性提高，且远高于高铬铸铁。     

烧结工艺对氧化铝-铝金属陶瓷材料性能的影响

利用粉末冶金方法制备氧化铝-铝金属陶瓷材料,研究其烧结工艺对其性能影响。结果表明,烧结温度从700℃逐渐升到1000℃且保温1 h的条件下,Al2O3/Al金属陶瓷的显微结构致密化程度逐渐降低,硬度逐渐降低,电阻率逐渐升高。在显微结构中颗粒呈连续分布且较大的为金属Al,颗粒呈不连续分布较且细小的为Al2O3。在700℃温度下,随保温时间延长,其显微结构组织越致密,硬度越高,电阻率越低。在700℃烧结3 h制备得到25 mass%Al2O3/Al金属陶瓷,其显微结构致密化程度较高,硬度为2203 HV,电阻率为0.0159Ω·m。     

Monel合金表面激光熔覆Ni基稀土合金空蚀性能

采用激光熔覆技术在Monel 400合金表面制备Ni基稀土合金熔覆层。利用SEM、EDS、XRD、显微硬度计及超声波金属材料空蚀仪等设备对熔覆层的组织形貌、相结构、硬度、空蚀性能及失效机制进行了系统研究。结果表明:Y_2O_3细化了熔覆层的组织,其组织主要由γ-Ni固溶体、Ni_3B和高硬度的Cr_(23)C_6和Cr_7C_3组成,熔覆层平均硬度可达9040MPa,抗空蚀性能是Monel400合金的8.7倍,熔覆层空蚀过程失效机制主要为枝晶干的冲蚀剥落,Ni基稀土合金熔覆层的细晶强化及空蚀过程中产生阻断晶界网状结构是提高其耐空蚀性能的关键。     

剪切载荷条件下镍基单晶合金裂纹扩展与微观结构演化行为研究

目前拉伸载荷下的镍基单晶合金的力学性能研究较为广泛,而剪切载荷对镍基单晶合金的力学性能也十分重要但缺乏研究。本文利用分子动力学方法研究了镍基单晶合金在剪切载荷下的裂纹扩展和微观结构演化,分析了应力-应变、势能和裂纹生长速率的变化。同时,揭示了温度和剪切应变率对裂纹扩展和微观结构演化的影响。结果表明,临界分切应力随温度的降低和应变速率的增大而增大;随着温度的升高以及剪切载荷下发生剧烈的热运动,裂缝表现为加速扩展的趋势;而在较高的应变率影响下,会形成位错塞积和孪晶,出现加工硬化现象。