化学沉积Ni-Mo-P和Ni-P镀层退火晶化组织及耐蚀性

目的研究化学沉积Ni-4.11%Mo-6.50%P和Ni-9.19%P合金镀层退火晶化转变特征,通过定量表征镀层的晶化程度、晶粒尺寸及结晶相的质量分数,建立显微组织与耐蚀性的关联。方法采用XRD衍射技术和Jade软件分析,定量表征镀层的晶化组织特征,由SEM/EDS测试确定镀层的成分及表面形貌,通过浸泡腐蚀实验及金相显微观察,对比两种镀层的耐蚀性。结果 Ni-Mo-P镀层在低于400℃退火时,只有Ni相结晶;在≥400℃退火时,发生Ni3P晶化反应,同时伴有Ni-Mo固溶体的形成,600℃时的晶化程度为88.13%。相比之下,Ni-P镀层中Ni3P相开始析出的温度降至300℃,600℃时的晶化程度达到91%。在相同温度进行热处理时,Ni-Mo-P镀层晶粒尺寸小于Ni-P镀层。在发生Ni3P晶化反应的温度下,两种镀层中Ni3P的晶粒尺寸总是大于Ni相。在0.5 mol/L的H2SO4中,对于Ni-Mo-P镀层,除300℃外,其他温度下的热处理均能显著改善其耐蚀性;而对于Ni-P镀层,镀态下具有最好的耐蚀性能。在10%的HCl溶液中,退火温度为600℃时,Ni-Mo-P镀层的耐点蚀性能更好;而Ni-P合金则相反,镀态及低温200℃退火后的耐点蚀性能最好。结论 Mo的共沉积提高了Ni-Mo-P镀层Ni3P的析出温度,降低了镀层的晶化程度及晶粒尺寸;与Ni-P镀层相比,高温退火的Ni-Mo-P镀层表现出了优异的耐点蚀性能,但耐硫酸均匀腐蚀的性能较差。

Ni-P/Ni-Mo-P镀层耐腐蚀性研究

通过在镀液中加入Na2 MoO4的化学沉积法对酸性Ni Mo P/Ni P双层化学镀工艺进行了研究。通过试验 ,确定了用连续施镀法制备此多元合金镀层的工艺。测定了镀层的性能 ,特别是对其耐腐蚀性能进行了重点研究。结果表明 ,镀层的成分及结构对其性能有关键的影响 ,双层镀镀层性能优于Ni P单层镀镀层性能。

化学镀非晶Ni-Mo-P与Ni-P镀层性能的对比

通过在镀液中加入Na2 MoO4的化学沉积法对酸性Ni-Mo -P镀层的形成进行了实验研究。运用正交设计法确定了此多元合金镀的最佳工艺。运用能谱法和X射线衍射实验对镀层的成分、结构及其性能进行了分析并与Ni-P镀层进行了对比研究 ,结果证明Ni-Mo -P镀层比Ni-P镀层的热稳定性高 。

化学镀非晶Ni-P/Ni-Mo-P合金形成机理

通过在镀液中加入Na2 MO4的化学沉积法对酸性Ni Mo P/Ni P双层化学镀的工艺进行了实验研究。通过一系列实验 ,确定了用连续施镀法制备此多元合金镀层的工艺。通过对镀层的成分与结构关系及镀层成分与工艺参数关系的实验研究 ,从热力学角度提出了非晶态双层镀镀层合金膜材的形成机理。

化学沉积Ni-P/Ni-Mo-P镀层的残余应力和腐蚀行为评价（英文）

通过化学沉积法制备Ni-P、Ni-Mo-P单镀层以及与其成分相同的Ni-P/Ni-Mo-P双镀层。采用纳米压痕法和AFM分析测量镀层表面和截面的残余应力,并用电化学法评估镀层在10%HCl溶液中的腐蚀行为,以获得镀层残余应力与腐蚀行为之间的关系。结果表明:Ni-P单镀层和Ni-P/Ni-Mo-P双镀层表现为残余压应力,分别为241和206 MPa;Ni-Mo-P单镀层呈现出257 MPa的残余拉应力。残余压应力阻止镀层中孔洞的生长,保护镀层的完整性。Ni-P/Ni-Mo-P双镀层比它们的单镀层具有更好的耐蚀性。此外,镀层的应力状态影响其腐蚀形式。

酸度对化学镀Ni-P和Ni-Mo-P的影响

研究了镀液pH值对Ni-P和Ni -Mo -P化学镀镀层的生成速度和镀层中Ni质量分数的影响 .结果表明 ,镀液的pH值不仅影响Ni的沉积速度 ,而且影响镀层中Ni的质量分数 ;镀层生成速度均随镀液pH值增大而出现极大值 ,但两者的位置有所不同 ;随镀液pH值增加 ,Ni-Mo -P镀镀层中w(Ni)出现极大值 ,而Ni-P镀则是pH值增至一定值后w(Ni)趋于平稳 ;镀层的生成速度与镀层中w(Ni)的最高点都出现在相同的酸度下 ,Ni -P镀镀液的最佳pH值为 5 .5 ,而Ni-Mo -P镀镀液的最佳pH值为 6.5 .

A3钢表面化学镀Ni-P/Ni-Mo-P双层镀层

在A3钢表面制备了以Ni-P镀层为底层、Ni-Mo-P镀层为表层的双层镀层,测试了单层Ni-P镀层、Ni-P/Ni-Mo-P双层镀层的结合力、腐蚀速率和阻抗谱图,并表征分析了单层Ni-P镀层、Ni-P/Ni-Mo-P双层镀层的成分以及腐蚀前后的形貌。结果表明,单层Ni-P镀层和Ni-P/Ni-Mo-P双层镀层都与基体结合良好,且都呈较为平整的胞状形貌;单层Ni-P镀层和Ni-P/Ni-Mo-P双层镀层都属于中磷镀层,Ni-P/Ni-Mo-P双层镀层表面几乎没有孔洞,胞状物大小相对均一,孔隙率仅为0.6个/cm^2,明显低于单层Ni-P镀层;在一定周期内,单层Ni-P镀层和Ni-P/Ni-Mo-P双层镀层都能对A3钢起到较好的保护作用,从而减轻A3钢腐蚀。与单层Ni-P镀层相比,Ni-P/Ni-Mo-P双层镀层的耐腐蚀性能更好,能为A3钢提供更长效的防护。

化学镀Ni-P与Ni-Mo-P合金镀层的耐蚀性能

研究了镀层结构(非晶态、晶态)以及Mo、P含量对化学镀Ni-P和Ni-Mo-P合金镀层在0.5MH2SO4溶液中的耐蚀性能的影响。结果表明:在相同合金镀层下,非晶态镀层具有较晶态镀层更好的耐蚀性能;镀层中Mo、P等元素的含量对镀层的耐蚀性能有着较大影响,其中P(非晶化元素)的影响最大。

Formation and thermal stability of amorphous Ni-Mo-P alloys

The experimental researches on the chemical deposition of Ni-Mo-P amorphous alloys were carried out by adding Na2 MoO4 into acidic solutions. The optimum technology conditions were obtained by orthogonal design experiments. The structures and the relationship between compositions and their thermal stability were studied by energy spectrum (EC), scanning electron micrograph and X-ray diffraction spectrum. Compared with Ni-P amorphous alloys, the Ni-Mo-P amorphous alloys have high crystallization temperature and thermal stability, and the hardness reaches its peak when the annealing temperature is 500 ℃. With the increase of the heat treatment temperature, the surface morphology of the alloys changes.

High-temperature tribological properties of Ni-P alloy coatings deposited by electro-brush plating

High-temperature tribological properties of Ni-P alloy coatings processed by electro-brush plating on 20CrMo steel have been investigated. A baU-on-disc configuration was employed and 4 mm diameter Si3N4 balls were used as static counterpart. All the wear tests were carried out at 450℃ for 180 rain without lubricants. The electro-brush plating Ni-P coating is amorphous in as-deposited condition, and it becomes polycrystalline with the formation of Ni and Ni3P after heat treatment at 450℃for 1 h. The friction coefficient of the Ni-P coating is just 50% of that of the 20CrMo steel at the friction temperature of 450℃. A mild adhesive wear mechanism was found for the electro-brush plating Ni-P coating tested at 450℃, whereas for the 20CrMo steel at the same temperature a mixed adhesive and abrasive wear mechanism was observed.

High-temperature Compressive Performance of Mg Alloy Foams Coated with Ni-P Layer

Mg/Ni hybrid foams were fabricated by the electroless method.The Ni-P(Nickel-Phosphorous)coatings were deposited on the surface of closed-cell Mg alloy foams.The composition,microstructure and phases of the Ni-P coatings were characterized by scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS)and X-ray diffraction(XRD),respectively.The compressive tests were performed on the Mg/Ni hybrid foams at 400℃using the Mg alloy foams as a reference.The experimental results show that the yield strength,plateau stress and energy absorption capacity of the closed-cell Mg alloy foams at high temperature were improved by the Ni-P coating.And there are four main modes for the Mg/Ni hybrid foam failure at 400℃,i e,shearing in cell wall,bending in cell edge,shedding and cracking in Ni-P coating.

Investigation on a Non-cyanide Plating Process of Ni-P Coating on Magnesium Alloy AZ91D

In this research we presented a non-cyanide plating process of Ni-P alloy coating on Mg alloy AZ91D. By applying a new process flow of electroless nickel plating in which zinc coating is used as transition of Ni-P coating on Mg alloy AZ91D, the process of copper transition coating plated in the cyanides bath can be replaced. A new bath composed of NiSO4 was established by orthogonal test. The results show that zinc transition coating can increase the adhesion and protect the Mg alloy substrate from the bath corrosion. The optimal plating bath composition is NiSO4·6H2O 20 g/L, NaH2PO2·H2O20g/L and C6H8O7·H2O 2.5 g/L, and optimal bath acidity and optimal plating temperature are pH 4.0 and 95℃, respectively. The present process flow is composed of ultrasonic cleaning→alkaline cleaning→acid pickling→activation→double immersing zinc→electroplating zinc→electroless nickel plating→passivation treatment. The present non-cyanide process of electroless nickel plating is harmless to our surroundings and Ni-P coating on Mg alloy AZ91D produced by present process possesses good adhesion and corrosion resistance.

Electrochemical behavior of Cu-Zn-Al shape memory alloy after surface modification by electroless plated Ni-P

The electrochemical behavior of Cu-Zn-Al shape memory alloy (SMA) with andwithout electroless plated Ni-P was investigated by electrochemical methods, in artificial Tyrode'ssolution. The results showed that Cu-Zn-Al SMA engendered dezincification corrosion in Tyrode'ssolution. The anodic active current densities as well as electrochemical dissolution sensitivity ofthe electroless plated Ni-P Cu-Zn-Al SMA increased with NaCl concentration rising, pH of solutiondecreasing and environmental temperature uprising. X-ray diffraction analysis indicated that aftersurface modification by electroless plated Ni-P, an amorphous plated film formed on the surface ofCu-Zn-Al SMA. This film can effectively isolate matrix metal from corrosion media and significantlyimprove the electrochemical property of Cu-Zn-Al SMA in artificial Tyrode's solution.

TEMPERATURE DEPENDENCE UPON VISCOSITY OF Ni-P ALLOY ON AMORPHOUS FORMATION

The viscous flow of amorphous alloys near T_gis closely related to the viscosity of liquid alloys. On the basis of the measured surface tension and density for Ni-P binary alloys,the correla- tion between the viscosity of the melt and viscous flow process of the amorphous alloy is inves- tigated.The relationship between viscosity and temperature for Ni-P alloys going from liquid to amorphous solid may be described by the following formula:

APPLICATION OF MAXIMUM ENTROPY METHOD TO CALCULATE RDF OF Ni-P AMORPHOUS ALLOY FROM X-RAY DIFFRACTION DATA

Experiments clarified that application of the maximum entropy method to calculate the RDF (radial distribution function)of the Ni-P amorphous alloy from fewer data of its X-ray diffraction data shows a higher resolution and good consistent with known results.It is be- lieved that this method is available for the analysis of amorphous structure.

Ni–P coating on AZ31 magnesium alloy and its crystallization

Amorphous Ni-P coating was plated on AZ31 magnesium alloy via the electroless plating technique, and the plated alloy was subsequently annealed. X-ray dif- fraction （XRD）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and differential scanning calorimetry （DSC） were used to characterize the coating. The results show that the hardness of the coating is much higher than that of bare magnesium alloy, which further increases after crystallization. The electrochemical polarization and salt spray tests show that the coating exhibits a much higher corrosion resistance than that of the bare magnesium alloy. Moreover, the crystallized coating still exhibits a much stronger corrosion resistance than that of the bare magnesium alloy, although its corrosion resistance is lower than that of the as-plated one.

Influence of RE elements on the performances of Ni-P coelectrodeposi-tion bath

Through adding the chlorides of La and Ce into Ni-P coelectrodeposition bath, the effects of rare earth （RE） elements on the performances of the bath have been investigated by hull cell tests, far and near cathodes tests, and so on. It is shown that the optimum contents of CeCl3, LaCl3 and their mixture are all 2 g/L. The bright zones of the Ni-P coelectrodeposition bath are greatly widened by the addition of RE, and this effect is more obvious in the low current density range. By the addition of RE, the current efficiency of the Ni-P coelectrodeposition bath is greatly increased. The results also show that RE elements can improve the dispersing capacity of the bath. It can be theoretically deduced that RE ions improve the cathodic polarization degree of Ni-P codeposition. This deduction has been confirmed by the cathodic polarization curves measured in the baths.

Study on the Technology of Ni-P Electroless Plating on the Mg Alloy

Base on the analysis for the corrosion mechanism of the Mg alloys,the technology of Ni-P directly electroless plating on the Mg-10Li-1Zn alloys was studied.The effects of the pre-treatment on the morphologies of substrate and plating films were investigated,The result shows that Ni-P electroless plating could be divided two steps:the induction period and the rapid deposition period.The Ni-P film is amorphous structure:A excellent Ni-P coating can be obtained under the optimal parameter.The Ni-P coating can obviously improve the corrosion resistance of Mg alloy in variety environment.

Synthesis and Characterization of Electroless Ni-P/Ni-Mo-P Duplex Coating with Different Thickness Combinations

In this work, a novel duplex Ni-P/Ni-Mo-P coating upon the aluminum（Al） substrate was synthesized via an electroless plating, i.e., the binary Ni-P coating as a transition layer and the ternary Ni-Mo-P coating on the top. It was found that the duplex coating was of a high hardness,large elastic modulus,low porosity and excellent corrosion resistance. In addition, experimental results revealed that for a total 20 μm coating thickness, the duplex coating with a 7 μm of the Ni-Mo-P coating exhibited the best corrosion resistance in 0.5 mol/L sulfuric acid solution, which was attributed to its compact structure and low porosity. This duplex Ni-P/Ni-Mo-P coating with a thin ternary Ni-Mo-P layer is expected to solve the problem of low deposition rate of ternary alloy coating and thereby may expand applications of Al and its alloys in the fields of machine manufacture and corrosion environment.

Electrodeposition mechanism of Ni-Mo-P alloy in the solution of ammoniac citrate

The induced codeposition mechanism of Mo, P and Ni from the solution of ammoniac citrate was studied by means of steady-state polarization, AC impedance and X-ray Photoelectron Spectroscopy (XPS). The result of electrochemical measurements proved that [NiCit(NH3)(2)](-) is the electro-active species of nickel, though nickel ions exist mainly as [NiCit(NH3)(3)](-) in ammoniac citrate. XPS experiments proved the existence of tetravalent molybdenum corresponding to MoO2 on the surface of some deposits. The intermediate product, MoO2, was probably reduced to Mo in the alloy deposit by atomic hydrogen adsorbed on the induced metal nickel. The reduction of H2PO2- occurs through two distinctive steps with PH3 as an, intermediate, which subsequently reacts with atomic hydrogen to form P in the alloy deposit. The electrodeposition mechanism was proposed in this paper.