Effect of hydrogen peroxide concentration on surface properties of Ni-Cr alloys

The effect of concentration of hydrogen peroxide （H2O2） on the surface properties of Ni-Cr alloys was studied. Surface roughness and surface morphology of Ni-Cr alloys were evaluated by surface profiler and scanning electron microscopy after being immersed in different concentrations of H2O2 for 112 h. Surface corrosion products of Ni-Cr alloys were analyzed by photoelectron spectrograph after being immersed in 0% and 30% H2O2. The order of increasing surface roughness of Ni-Cr alloys after being immersed in different concentrations of H2O2 was 0〈3.6%〈10%〈30%. As the concentration of hydrogen peroxide increased, the surface roughness of Ni-Cr alloys increased and the surface morphology showed different degrees of corrosion. According to the XPS results, the corrosion products formed on the outmost surface layer of the studied samples are Ni（OH）2 and BeO.

Density of Liquid Ni-Cr Alloy

The density of liquid Ni-Cr alloy was measured by a modified sessile drop method. The density of liquid Ni-Cr alloywas found to decrease with increasing temperature and Cr concentration in the alloy. The molar volume of liquidNi-Cr alloy increases with increasing the Cr concentration in the alloy. The molar volume of Ni-Cr alloy determinedin the present work shows a positive deviation from the linear molar volume.

Ni-Cr alloy electrodepositing technology on Fe substrate and coating performance

The Ni-Cr alloy electrodepositing technology on iron substrate in the chlorid-sulfate solution and the impacts of main processing parameters on coating composition were studied. The optimal Ni-Cr alloy electrodepositing conditions are that the cathode current density is 16 A/dm^2,the plating solution temperature is 30℃ and the pH value is 2.5. The bright, compact coating gained under the optimal conditions has good cohesion and 24.1% Cr content. The results show that the coating is composed of crystalline, the average grain size is 82 nm and the higher the Cr content of coating, the larger the rigidity, and the higher the corrosion resistance. The rigidity of coating reaches 78.6(HR30T) and the passivation area broadens to 1.4 V when the Cr content of coating is 24.1%.

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 CeO_2 on Microstructure and Bond Strength of Fe-Ni-Cr Alloy

Fe-Ni-Cr alloy powders with and without 0.4% CeO_2 were flame sprayed on the surface of 1045 carbon steel substrate. The effect of rare earth oxide CeO_2 on the interface layer and microstructure was investigated by X-ray diffraction analysis, SEM and EDS. Based on our previous work, comparison on the microstructure of a Fe-Ni-Cr alloy with and without 0.4% CeO_2 addition was made. The correlation between the microstructure and bond strength was studied. The addition of CeO_2 in Fe-Ni-Cr alloy shows promise results for providing good bonding strength as well as tribological properties. The results show that the hardness of the coatings can be improved by addition of 0.4% CeO_2, and the shape of powders is more spheroidal. The combination of three aspects, namely small, well-distributed microstructure, the well-distributed matrix and promotion of diffusion leads to the improvement in bond strength of Fe-Ni-Cr alloy with addition of 0.4% CeO_2.

Density of Ni-Cr Alloy in the Mushy State

The density of Ni-Cr alloy in the mushy state has been measured using the modified sessile drop method. The density of Ni-Cr alloy in the mushy state was found to decrease with increasing temperature and Cr concentration in alloy. The molar volume of Ni-Cr alloy in the mushy state therefore increases with increasing the Cr concentration in alloy. The ratio of the difference of density divided by the temperature difference between liquidus and solidus temperatures decreases with increasing Cr concentration. The density of the alloy increased with the precipitation of a solid phase in alloy during the solidification process. The temperature dependence of the density of alloy in the mushy state was not linear but biquadratic.

Influence of the Electrode Distance on Microstructure and Corrosion Resistance of Ni-Cr Alloyed Layers Deposited by Double Glow Plasma Surface Metallurgy

Ni-Cr alloyed layers were synthesized on the surface of Q235 mild steel by double-glow plasma surface metallurgy with different electrode distance.The microstructure and phases of the alloyed layer were characterized by scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),and X-ray diffraction(XRD).The corrosion behavior of the Ni-Cr alloyed layers both in 3.5%NaCl and 0.5 M H_(2)SO_(4) solution were systematically investigated by open-circuit potential(OCP),potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The obtained results reveal that the Ni-Cr alloyed layer consists of a deposited layer and an inter-diffusion layer.With increasing the electrode distance,the relative thickness,microstructure and phase composition of the Ni-Cr alloyed layers vary greatly.Polarization data show the Ni-Cr alloyed layer with the electrode distance of 15 mm has highest corrosion resistance and lowest corrosion rate,while EIS results reveal the same trend.The highest protective efficiency in 3.5%NaCl and 0.5 M H_(2)SO_(4) solution are 99.23%and 99.92%,respectively,obtained for the Ni-Cr alloyed layer with 15 mm electrode distance.When the electrode distance is too large,a thin and porosity Ni-Cr alloyed layer,caused by low plasma density and Kirkendall effect,will be obtained,and will decrease the protective efficiency in corrosive medium.

Electrodeposition of Ni-Cr alloy on aluminum substrate

Ni-Cr alloys with mass fraction of 1.4%23.9%Cr, 76.1%98.6%Ni, and hardness of 70.5 80.5HR were electrodeposited on aluminium substrate from the trivalent chromium sulphate-chloride solution using citric acid as complexing agent. The aluminium was pretreated by means of degreasing and eroding, polishing and twice chemical immersion of zinc. The effects of electrodeposition parameters such as current density, temperature, pH value and bath concentration on the composition and hardness of deposits were investigated. The results show that the Cr content increases with the increase of current density and the decrease of temperature, and that it increases with the increase of pH value to a maximum and then decreases. The increase of Cr content leads to the increase of hardness of the Ni-Cr layers. The deposits with high Cr content are of good corrosion resistance. Good adherence of Ni-Cr deposits to aluminium substrate is obtained. The Ni-Cr alloys are the Ni-Cr solid solution with fcc crystalline structure. The Ni-Cr alloy deposits are fine, bright and smooth and compact.

Electroplating process of amorphous Fe-Ni-Cr alloy

A novel process of electroplating amorphous Fe Cr Ni alloy in chloride aqueous solution with Fe(Ⅱ), Ni(Ⅱ) and Cr(Ⅲ) was reported. Couple plasma atomic emission spectrometry (ICP AES), X ray diffractometry(XRD), scanning electronic microscopy(SEM), microhardness test and rapid heating cooling method were adopted to detect the properties of the amorphous Fe Ni Cr deposit, such as composition, crystalline structure, micrograph, hardness, and adherence between deposit and substrate. The effects of the operating parameters on the electrodeposit of the amorphous Fe Ni Cr alloy were discussed in detail. The results show that a 8.7?μm thick mirror like amorphous Fe Ni Cr alloy deposit, with Vicker’s hardness of 530 and composition of 45%～55% Fe, 33%～37% Ni, 9%～23% Cr was obtained by electroplating for 20?min at room temperature(10～30?℃), cathode current 10～16?A/dm 2, pH=1.0～3.0. The XRD patterns show that there only appears a broad hump around 2 θ of 41?°～47?°for the amorphous Fe Ni Cr alloy deposit, while the SEM micrographs show that the deposit contains only a few fine cracks but no pinholes.

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.

Microstructure and Wear Resistance of Ni-Cr Alloy Laser Cladding Layer with High Cr Content

Four kinds of Ni-xCr alloy laser cladding layers(x=20,40,60 and 80,wt%)were prepared by high-speed laser cladding technique,and the relationship between microstructure and wear resistance of Ni-Cr alloy laser cladding layers with different Cr contents was investigated.The results show that the four Ni-Cr alloy laser cladding layers all have reticulated dendritic structures.Among them,Ni-20Cr and Ni-40Cr are single-phaseγ-(Ni,Cr)solid solutions,and their wear mechanisms are adhesive wear and abrasive wear.With the increase in Cr content,Ni-60Cr and Ni-80Cr areγ-(Ni,Cr)phase and Cr phase,as well as Cr-rich precipitates,and their wear mechanisms are adhesive wear,abrasive wear and fatigue wear.A moderate increase in Cr content can enhance the hardness and wear resistance of Ni-Cr alloy laser cladding layer.However,excessive addition of Cr results in the precipitation of Cr-rich precipitates.The hardness of these precipitates is 2430.4 MPa,which is lower than the hardness of the Ni-60Cr matrix(4024.86 MPa)and Ni-80Cr matrix(7022.68 MPa).A hardness transition zone exists between the Cr-rich precipitates and the matrix.Cracks are likely to initiate and expand in this zone,leading to deep spalling,which is not conducive to the wear-resistant properties of the laser cladding layer.Ni-80Cr has the highest hardness,but its high Cr content leads to a large number of penetrating cracks and Cr-rich precipitates on the surface,ultimately resulting in the worst wear resistance.Ni-60Cr exhibits the best wear resistance due to its high hardness and dense microstructure.

Short-range ordering plays a determining role in the low-cycle fatigue life improvement of fcc metals: A conclusive study on low solid-solution hardening Ni-Cr alloys

The effect of short-range ordering (SRO) on the low-cycle fatigue (LCF) behavior of low solid-solution hardening Ni-Cr alloys with high stacking fault energies (SFEs) was systematically studied under cycling at constant total strain amplitude (Δε t /2) in the range of 0.1%–0.7%. The results show that an inducement of SRO structures can notably improve the fatigue life of the alloy regardless of Δε t /2, and several unique fatigue characteristics have been detected, including the transition of fatigue cracking mode from intergranular cracking to slip band cracking, the non-negligible evolution from non-Masing behavior in pure Ni to Masing behavior in the Ni-40Cr alloy, and the secondary cyclic hardening behavior in the Ni-10Cr and Ni-20Cr alloys. All these experimental phenomena are tightly associated with the transformation in cyclic deformation mechanisms that is induced by SRO based on the “glide plane softening” effect. Furthermore, a comprehensive fatigue life prediction model based on total hysteresis energy has been reasonably proposed, focusing on the analyses of the macroscopic model parameters (namely the fatigue cracking resistance exponent β and the crack propagation resistance parameter W 0 ) and microscopic damage mechanisms. In brief, on the premise that the effects of SFE and friction stress can be nearly ignored, as in the case of the present low solid-solution hardening Ni-Cr alloys with high SFEs, an enhancement of SRO in face-centered cubic metals has been convincingly confirmed to be an effective strategy to improve their LCF performance.

Ni-Cr薄膜换能组件静电响应特性与发火概率预测研究

针对电火工品在静电放电影响下可能发生误发火的问题,以Ni-Cr薄膜换能组件为研究对象,提出了一种分析其在人体静电放电下的响应特性,并预测发火概率的方法。首先,介绍了Ni-Cr薄膜换能组件系统架构,并建立了电火工品静电放电等效电路模型;其次,研究了Ni-Cr薄膜换能组件静电放电响应特性,分析了换能组件尺寸和放电电压对薄膜桥区温度的影响规律;最后,构建了Ni-Cr薄膜换能组件在统计特征下的输入条件,确定了换能组件失效判据,进而结合发火感度试验与数理统计方法,实现了在静电放电条件下电火工品发火概率的预测。研究结果表明:预测发火概率与试验值误差不超过5%,验证了本文方法的有效性。

退火和变形温度对Ti-Ni-Cr形状记忆合金弹簧低温超弹性的影响

利用拉伸试验研究了350~800℃退火态Ti-50.8Ni-0.3Cr合金弹簧在-20~20℃温度范围变形时的低温超弹性。结果表明,在350~800℃温度范围退火时,随退火温度升高,该合金弹簧对外输出应力先降低再升高,而后趋于稳定。在-20~20℃温度范围变形时,随变形温度升高,该合金弹簧对外输出应力增大。要使该合金弹簧在-20℃下获得残余应变较小的超弹性,可对其进行350~400℃或550~800℃退火处理;要使该合金弹簧在-10~20℃下获得残余应变较小的超弹性,可对其进行350~500℃退火处理;要使该合金弹簧在-20~20℃下获得较大的能耗,可对其进行450~800℃退火处理。随退火温度升高,该合金弹簧的应变恢复率降低;随应力-应变循环次数增加,该合金弹簧的应变恢复率先降低后趋于稳定。预循环训练能明显提高该合金弹簧应变恢复率的稳定性。

贴膜式Ni-Cr换能元设计及性能研究

通过热压工艺将5μm的Ni-Cr薄膜附着在聚酰亚胺薄膜上制备了贴膜式Ni-Cr薄膜,采用激光刻蚀加工工艺制备了贴膜式Ni-Cr换能元电桥,仿真优化设计了蝶形、S形换能元电桥,并开展了2种形状电桥的贴膜式Ni-Cr换能元的伏安特性、最大不熔断电流、50 ms脉冲恒流电爆特性以及发火特性试验研究。研究结果表明:桥区长度为3 mm的换能元电桥在1 A 5 min恒流激励后桥区温度最低;贴膜式Ni-Cr换能元在33μF电容放电时,随着充电电压的升高断桥时间缩短,蝶形和S形未发生断桥的电压分别为16,20 V;蝶形和S形换能元在5 min恒流脉冲输入下的最大不熔断电流分别为1.3,1.2 A;在50 ms脉冲恒流电爆时,随着施加电流幅度的不断增加,其工作电压也不断增高,其断桥时间越来越短,S形换能元和蝶形换能元分别在2.4,2.3 A时电桥未发生爆炸;33μF、28 V电容放电下贴膜式Ni-Cr换能元可以点燃斯蒂芬酸铅,并正常发火。

Relationship between the unique microstructures and behaviors of high-entropy alloys

High-entropy alloys(HEAs),which were introduced as a pioneering concept in 2004,have captured the keen interest of nu-merous researchers.Entropy,in this context,can be perceived as representing disorder and randomness.By contrast,elemental composi-tions within alloy systems occupy specific structural sites in space,a concept referred to as structure.In accordance with Shannon entropy,structure is analogous to information.Generally,the arrangement of atoms within a material,termed its structure,plays a pivotal role in dictating its properties.In addition to expanding the array of options for alloy composites,HEAs afford ample opportunities for diverse structural designs.The profound influence of distinct structural features on the exceptional behaviors of alloys is underscored by numer-ous examples.These features include remarkably high fracture strength with excellent ductility,antiballistic capability,exceptional radi-ation resistance,and corrosion resistance.In this paper,we delve into various unique material structures and properties while elucidating the intricate relationship between structure and performance.

Gd改性Ni-Cr钎料钎焊金刚石组织和性能研究

本研究旨在减少钎焊金刚石的热损伤,提高钎焊金刚石的力学性能。采用Gd改性的Ni-Cr合金钎料,在1080℃保温5 min对金刚石进行真空感应钎焊试验,并利用SEM、EDS及XRD对钎料的微观组织和金刚石焊后界面微结构进行测试分析。结果表明,Gd的添加提高了Ni-Cr合金钎料的力学性能,钎料中生成了两种新的稀土化合物(Gd_(2)Ni_(17)和GdNi_(5))。添加适量的Gd可提高金刚石的出露度,且钎焊接头中生成的新型Gd_(2)Ni_(17)化合物有利于减少钎焊金刚石的热损伤。此外,当Gd的添加量为0.8%时,金刚石的暴露量达到其自身高度的62.1%,力学性能测试证实使用该钎料钎焊的金刚石的静压强度和磨削性能高于使用纯镍铬合金钎焊的钻石。

Microstructure and damping properties of LPSO phase dominant Mg-Ni-Y and Mg-Zn-Ni-Y alloys

This work studied the microstructure,mechanical properties and damping properties of Mg_(95.34)Ni_(2)Y_(2.66) and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys systematically.The difference in the evolution of the long-period stacked ordered(LPSO)phase in the two alloys during heat treatment was the focus.The morphology of the as-cast Mg_(95.34)Ni_(2)Y_(2.66)presented a disordered network.After heat treatment at 773 K for 2 hours,the eutectic phase was integrated into the matrix,and the LPSO phase maintained the 18R structure.As Zn partially replaced Ni,the crystal grains became rounded in the cast alloy,and lamellar LPSO phases and more solid solution atoms were contained in the matrix after heat treatment of the Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloy.Both Zn and the heat treatment had a significant effect on damping.Obvious dislocation internal friction peaks and grain boundary internal friction peaks were found after temperature-dependent damping of the Mg_(95.34)Ni_(2)Y_(2.66)and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys.After heat treatment,the dislocation peak was significantly increased,especially in the alloy Mg_(95.34)Ni_(2)Y_(2).66.The annealed Mg_(95.34)Ni_(2)Y_(2.66)alloy with a rod-shaped LPSO phase exhibited a good damping performance of 0.14 atε=10^(−3),which was due to the difference between the second phase and solid solution atom content.These factors also affected the dynamic modulus of the alloy.The results of this study will help in further development of high-damping magnesium alloys.

High corrosion and wear resistant electroless Ni–P gradient coatings on aviation aluminum alloy parts

A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.

Y元素对Ni-Cr非晶钎料钎焊金刚石组织和性能的影响

钎焊金刚石工具因化学冶金结合方式而具备较高的结合强度,在陶瓷、半导体和玻璃等硬脆性材料的加工行业及轨道交通、航空航天等领域中拥有广泛的应用前景。虽然Ni基钎料钎焊金刚石工具在结合强度、耐磨性及服役环境方面具有一定的优势,但是较高的钎焊温度和化学侵蚀会对金刚石磨粒造成较为严重的热损伤,从而影响金刚石工具的工作效率和服役寿命。为了降低钎焊过程中金刚石的热损伤,采用掺杂Y元素的Ni-Cr非晶钎料钎焊金刚石,通过SEM研究了钎焊金刚石试样的界面微观形貌,使用拉曼光谱仪分析了钎焊金刚石试样的石墨化程度,同时还探究了钎焊金刚石试样的力学性能。结果表明,当Y元素的质量分数为0.8%时,钎焊试样的金刚石形貌最为完整,钎焊层硬度最高为533 HV_(0.1),金刚石出露度较高为76.2%且石墨化程度较低。另外,Y元素的添加细化了碳化物的尺寸,降低了碳化物微裂纹的产生。相较于未添加Y元素的钎焊试样,添加Y元素的金刚石钎焊试样的抗压强度提升了约50.4%,磨削性能提高了43.5%,金刚石的脱落数量最少。表明,用Y元素掺杂的Ni-Cr非晶钎料可成功制备出钎焊金刚石试样,同时还降低了钎料中的触媒元素对金刚石的侵蚀作用,改善了热损伤和磨削性能。本研究为非晶钎料在钎焊金刚石工具领域中的应用提供了可靠的理论支持,并为相关工业生产提供了新的技术路径,在降低生产成本和推动绿色生产方面具有一定的实际意义。