显微组织对Ni-Cr合金热腐蚀行为的影响

采用机械合金化法和真空熔炼法制备了不同显微组织的Ni-20Cr（质量分数，％，下同）合金，并研究其在950℃，75％Na2SO4＋25％K2SO4（质量分数，下同）盐膜下的热腐蚀行为。结果表明：细晶的机械合金化Ni-20Cr合金热腐蚀后表面形成了单一连续的Cr2O3外氧化膜，有效地阻止了硫的向内扩散，延长了热腐蚀过程的孕育期，呈现出较普通晶粒尺寸的熔炼Ni-20Cr合金更好的抗热腐蚀性能。     

Steam oxidation resistance of two-layered Ni-Cr and Al APS coating for USC boiler applications

Thermal spray of Ni-Cr and Al coatings was attempted on modified 9Cr-1Mo steel, to evaluate their steam oxidation resistance. Atmospheric plasma spray (APS) coatings of 50Ni-50Cr as undercoat and Al topcoat were attempted with the aim that the pores produced by 50Ni-50Cr undercoat can be filled with Al topcoat during the steam oxidation. The steam oxidized samples evinced the Ni and Cr diffusion towards the Al coating structure and changed the topcoat in to the Ni-Al intermetallics. Though the two-layered coating exhibited an excellent performance against the steam oxidation for the base steel substrate till 3000 h of test, the top layers of the coating underwent significant internal oxidation.     

碳钢表面离子镍铬共渗的研究

本文主要介绍了碳钢双层辉光离子镍铬共渗的试验结果,探讨了渗层厚度与镍铬共渗工艺参数的关系。试验表明,镍铬共渗层厚度取决于共渗温度、保温时间和试样材料,其变动范围0～300μm,共渗层中的镍铬含量可在0～90%的范围内变动。此外,还列举了双层辉光离子镍铬共渗工艺在碳钢钢板及碳钢零件上的应用。     

The high-temperature oxidation of Ni-20%Cr alloys containing various oxide dispersions

The oxidation behavior of Ni-20%Cr alloys containing approximately 3 vol.% Y₂O₃, ThO₂, and A1₂O₃ as dispersed particles has been examined in the temperature range 900 to 1200° C in slowly flowing oxygen at 100 Torr. The results show that the oxidation behavior of the Y₂O₃-, ThO₂-, Al₂O₃-, and Ce0₂-containing alloys is very similar and that some anomalies in the behavior of the ThO₂-containing alloy might be explained by the slower rate of chromium diffusion in this coarse-grained alloy. Two Al₂O₃-containing alloys were studied. One with a relatively coarse dispersoid size behaved in a manner analogous to a dispersion-free Ni-30% Cr alloy at 1100°C. The other alloy contained a dispersion of fine Al₂O₃ particles and behaved exactly like the Y₂O₃-containing alloy at 1000 and 1100°C, but at 1200° C oxidized at a faster rate. It has been shown that the adherent scales on dispersion-containing alloys have a stabilized fine grain size, whereas the nonadherent scales on dispersion-free alloys undergo grain growth.This work has been supported by the Naval Air Systems Command under Contract No. N00019-72-C-0190.     

Comparison between Ni-Cr-40vol%TiC wear-resistant plasma sprayed coatings produced from self-propagating high-temperature synthesis and plasma densified powders

Plasma sprayed Ni-Cr-40vol%TiC coatings produced from powders obtained by self-propagating hightemperature synthesis (SHS) and plasma densification (PD) processes are characterized. Chemical composition, microstructure, and mechanical properties, such as microhardness and wear resistance, are evaluated and compared. SHS coatings exhibit good sliding wear performance. The exact stoichiometry of titanium carbide inclusions in the metallic matrix affects the dimension of the crystal lattice parameter and was investigated by examining the shift of x-ray diffraction (XRD) peaks of the TiC. A value of the combined carbon/titanium ratio of about 0.6 was calculated for both powders, thus excluding the influence of the stoichiometry of the carbide inclusions on the wear properties of the coatings.     

On the electrochemical nature of hot-corrosion attack in Ni-Cr alloys

Hot-corrosion attack on gas-turbine components has been a problem of practical importance for over two decades. The nature and the extent of corrosion are influenced by the type of contaminants, the alloy constituents, and temperature. The hot-corrosion process is quite complex. There is controversy regarding the role of alloying elements, and whether the process is chemical or electrochemical in nature. In this investigation, an attempt has been made to investigate the role of Al and Ti in influencing the hot-corrosion attack of Ni-20 wt. % Cr alloys in molten Na₂SO₄-NaCl mixtures. It was found that Ni-Cr-Al alloys undergo a localized, heavy-blister attack under certain experimental conditions which is electrochemical in nature. An electrochemical model has been proposed which can satisfatorily explain the nature and kinetics of the localized blister corrosion.     

Ni-Cr/BN烧结工艺过程探讨

研究了烧结温度对Ni-Cr/BN组织和性能的影响。结果表明BN的加入降低了材料的烧结温度;随着烧结温度的提高材料的强度、硬度和密度都有所提高;该材料的合适烧结温度在1000℃-1100℃之间。     

不同配比Ni-Cr系涂层非线性动力学系统的抗腐蚀性能研究

采用非线性动力学系统的BP数据网络进行管材涂层腐蚀性能预测。首先采用增重法获取9种腐蚀工况下的增重数据,将获取的数据用于构建BP神经网络模型,通过传输和反演操作设置拓扑结构为6×15×1的BP神经网络,然后基于90组实验数据用于验证和评价BP神经网络预测模型,最后通过对优选出的涂层进行Ni-Cr系涂层的机理分析,从而解决生物质电站锅炉"四管"的腐蚀问题,研发的抗腐蚀涂层具有较好的经济性和实用性。     

Improving corrosion resistance of Q235 steel by Ni-Cr alloyed layer

Ni-Cr alloyed layer was formed on surface of Q235 steel by double glow plasma surface metallurgy to improve the corrosion resistance of substrate. The composition and microstructure of alloyed layer was analyzed by SEM and XRD. Potentiodynamic polarization and electrochemical impedance spectroscopy was applied to evaluate the corrosion resistance of the alloyed layer. The results showed working pressure had a great effect on structure of Ni-Cr alloyed layer, and the dense and smooth alloyed layer was prepared at 50 Pa working pressure. Compared with substrate, Ni-Cr alloyed layer exhibited higher corrosion potential, lower corrosion current density and larger charge transfer resistance, which indicated that Ni-Cr alloyed layer significantly modified the corrosion resistance of Q235 steel.     

Effect of Substrate Surface Roughness on Properties of Ni-Cr Alloy Thin Film

The effect of surface roughness of aluminum oxide (95%) substrate on the properties of Ni-Cr alloy thin film is studied.The thin films are prepared on the substrates with different roughness by using magnetron sputtering.The micro-structure,adhesive and electrical properties of the thin films were investigated by using scanning electron microscopy,scratch method and four-probe method.The burst voltage and current of the thin film transducers with different substrates were measured according to D-optimization method.The results show that the particle size,structural defect,resistivity and adhesion strength of the thin film increase with the increase of the substrate roughness.The difference among the burst time of the samples with difference substrate roughness gradually decreases with the increase of stimulation amount.The burst time is approximate to 20 μs in the charging voltage of 37 V.