热处理对化学镀Ni-B合金镀层微观结构的影响

采用XRD和TEM研究了热处理对化学镀Ni-B合金镀层微观组织结构的影响。XRD分析表明,Ni-B合金镀层主要为非晶态结构,随着热处理加热温度的不断升高,镀层逐步由非晶态向晶态转变。TEM分析表明,Ni-B合金镀层为非晶与纳米晶组合的混晶态结构,非晶镀层经过350℃热处理以后转变为晶态镀层。     

化学镀Ni-B和Ni-B/BN镀层微动磨损性能研究

采用化学镀液相沉积技术,以钛合金TA7为基体材料,分别镀覆Ni-B合金镀层和Ni-B/BN自润滑复合镀层,对镀层进行微动磨损性能测试和镀层表面形貌观察.结果表明:在微动磨损过程中完全滑移状态下,Ni-B/BN镀层中六方BN微粒具有类似石墨层状结构,该Ni-B/BN镀层具有自润滑性能,使其摩擦因数比Ni-B镀层低,即Ni-B/BN复合镀层在滑移区耐微动磨损性能要优于化学镀Ni-B二元合金镀层.     

化学镀Ni-B合金镀层的微观结构

采用XRD和TEM方法研究了5种化学镀N i-B合金镀层镀态下的微观组织结构,以及还原剂KBH4含量对镀层微观组织的影响。XRD分析表明,N i-B合金镀层主要为非晶态结构。TEM分析表明,N i-B合金镀层为非晶与纳米晶组合的混晶态结构,而且随镀液中KBH4含量的增加,N i-B合金镀层中的非晶态组织增加,纳米晶态组织减少,经历由纳米晶态→混晶态→非晶态的转变过程。采用XRD和TEM相结合方式,才得到准确的分析结果。     

化学镀Ni—B合金工艺研究

近年来,化学镀Ni-B合金层的优异功能特性越来越受到各国化学镀工作者的重视,但它在我国还是个空白.本文详细讨论了二甲氨基硼烷化学镀Ni-B镀液中各种成分和工艺条件对Ni-B合金沉积速度和镀层含硼量的影响,确定了柠檬酸铵做配位剂的二甲氨基硼烷化学镀Ni-B合金的最佳工艺条件。按此条件可以稳定地获得含硼量为1～5％的Ni-B镀层。     

Wear and corrosion resistance behaviours of autocatalytic electroless plating

Nickel–boron coatings were deposited on steel and aluminium substrates. Their morphology, roughness, hardness, wear resistance and electrochemical properties were investigated. A comparison between the coated systems was carried out. The plated aluminium was found to present better roughness and corrosion resistance behaviours than coated steel. The wear resistance of both coated systems is very similar. The aluminium-based system presents a more noble electrochemical behaviour than the coated steel.     

The effect of SiC particles added in electroless Ni-P plating solution on the properties of composite coatings

To verify the relationship between the properties of composite coatings prepared on Q235 steel and the SiC content of electroless Ni-P-SiC composite coatings, systematic experiments with varied SiC contents and surfactants have been conducted. The experimental results indicated the approximate linear relation between the SiC content and the hardness of composite coatings. With the increasing of SiC content, wear resistance increases correspondingly. In particular, the effect of SiC content on the corrosion resistance of Ni-P-SiC composite coatings immersed in different corrosive solutions (i.e. 5% H₂SO₄, 20% NaOH and 3.5% NaCl) is explored, followed by a comparative analysis of the corrosion resistance between Ni-P and Ni-P-SiC coatings. Corrosion test indicates that NaOH solution makes no differences in the corrosion resistance between Ni-P coatings and electroless Ni-P-SiC composite coatings, both being uncorroded. Exposed to NaCl solution, the corrosion resistance of electroless Ni-P-SiC composite coatings decreases gradually with the increasing of SiC content in coatings. In H₂SO₄ solution, the corrosion resistance of coatings increases initially and decreases afterwards with the sustained increasing of SiC content in coatings, and the optimized corrosion resistance is obtained at a SiC content of 9.41 wt.%. Finally, a competent electroless Ni-P-SiC composite plating process producing a high wear resistance and sound corrosion resistance of the coatings is obtained.     

A new method for electroless Ni-P plating on AZ31 magnesium alloy

Coating Ni-P films on AZ31 magnesium alloys via electroless plating and organic coatings (organsilicon heat-resisting varnish), was studied. An organic coating was proposed as the interlayer between Ni-P coating and AZ31magnesium alloy substrate, to replace the traditional chromium oxide plus HF pretreatment. The Ni-P deposited on the interlayer was also characterized by its structure, morphology and corrosion-resistance. The interlayer on the substrate not only reduces the corrosion of magnesium during Ni-P plating process, but also reduces the potential difference between the matrix and the second phase. The result of the cross-cut test indicates the adhesion between the substrate and the interlayer is good enough. A Ni-P film with fine and dense structure was obtained on the AZ31 magnesium alloy. The electrochemical measurements show that the sample with Ni-P film exhibits lower corrosion current density and more positive corrosion potential than the substrate. Furthermore, the Ni-P coating on the AZ31 magnesium alloy exhibits high corrosion resistance in the rapid corrosion test illustrated in this paper. The method proposed in this work is environmentally friendly: no fluoride or hexacalent chromium compounds are used. In addition, it provides a new concept for plating the metals, which are considered difficult to plate due to high reactivity.     

热处理温度对Ni-Fe-P化学镀层性能的影响

将表面经过Ni-Fe-P化学镀的35CrMo钢在不同温度下进行热处理,通过XRD、显微硬度计、电化学试验等手段研究热处理温度对镀层性能的影响。结果表明,经热处理后,镀层具有较高的硬度,400 ℃时,达到最高值881.7 HV0.5;经过热处理的镀层与基体有很好的结合力;镀层经200 ℃热处理后耐蚀性能提高,经400 ℃热处理后镀层耐蚀性降低,当热处理温度增加到600 ℃时,镀层的耐蚀性有所回升。     

温度对AZ31B镁合金表面化学镀Ni-B合金性能的影响

试验研究了镀液温度对AZ31B镁合金表面化学镀Ni-B合金性能的影响。结果表明:镀液温度对化学镀Ni-B合金的镀速、成分、形貌、耐腐蚀性有很大的影响,当温度为80℃时,镀速较大,镀层均匀、紧凑、细小,耐腐蚀性良好。     

The effect of processing gas on corrosion performance of electroless Ni-W-P coatings treated by laser

An investigation of the microstructural and corrosion characteristics of electroless Ni-5.5 W-6.5P coatings on steel substrates after laser treatment in argon and air is presented. The microstructural characteristics of the coatings, in terms of crystallisation, grain size, microstrain, porosity as well as surface chemistry, were examined using quantitative X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical tests, using potentiodynamic polarisation in 0.5 M H₂SO₄ solution and electrochemical impedances spectroscopy (EIS) in 3.5% NaCl solution, were undertaken to evaluate the corrosion behaviour of the coatings. The results indicated that the laser-treated coatings consisted of nanocrystalline Ni and Ni₃P phases, along with retained amorphous phase; further, the dimensions of the Ni crystallites were larger than those of Ni₃P. The laser-treated coating in argon revealed the presence of submicron scale porosity, while no porosity was evident in the coating surface treated by laser in air. The uniform corrosion revealed in 0.5 M H₂SO₄ solution is mainly determined by the microstructural characteristics of the coating. Pitting corrosion in 3.5% NaCl solution depended on the amount of porosity on the surface. The laser-treated coating in air exhibited better corrosion resistance in both acidic and chloride environments than that laser-treated in argon.     

中温酸性化学镀Ni-P合金耐蚀性能研究

为提高化学镀Ni-P合金耐蚀性能,以Q235钢为待镀基体,在中温的酸性条件下,采用正交试验方法得到镀层耐蚀性最佳的工艺条件为:镀液pH值 5.2;Ni2 与H2PO2-的摩尔比为0.48;复合络合剂乳酸15mL/L 丙酸5mL/L;加速剂NaF 0.4g/L;热处理温度500 ℃.在此条件下,腐蚀电流为2.166×10-5A,可较好地提高镀层耐蚀性.     

微过滤及超过滤技术在化学镀镍工艺中的应用研究

实验表明在以工业级药品为原料的化学镀镍工艺中应用微过滤或超过滤技术,可显著地改善镀层的耐蚀性,其效果可与以试剂级药品为原料的化学镀镍层媲美。     

ZL104合金表面化学镀镍磷合金层的研究

在ＺＬ１０４合金表面上进行Ｎｉ－Ｐ与Ｎｉ－Ｃｕ－Ｐ化学镀,以提高ＺＬ１０４合金材料的耐蚀性与耐磨性。结果表明：化学镀可以显著提高ＺＬ１０４合金表面的硬度,并改善其在５％ＮａＣｌ溶液中的耐蚀性;在２００～５２０℃温度下热处理后,镀层的硬度显著提高,但耐蚀性略有降低,这可能与镀层中的析出物Ｎｉ３Ｐ析出有关。     

Ni-B合金化学镀包覆TiB2粉的研究

为改善TiB2粉末物性,采用化学镀工艺对其进行包覆Ni—B合金处理。经Hall流动仪检测,包覆后粉末松装密度由1．15～1．17g／cm^3增加到1．38～1．39g／cm^3,粉末流动性由包覆前粉末堵塞霍尔流动性测量仪喷嘴变为94～97s／50g;SEM形貌扫描分析表明包覆效果较好,包覆率大于90％;补加镀液包覆效果更好,镀层更致密,包覆率大于95％。     

非晶态Ni-B镀层组织结构与性能研究

对非晶态Ni-B镀层的组织结构和性能进行研究,结果表明:非晶态Ni-B镀层以层片状沉积,表面具有胞状结构。经300°×1h热处理,镀层已经晶化,并析出了细小的Ni_3B相;提高加热温度,Ni_3B粒子明显长大。非晶态Ni-B镀层的镀态硬度为HV_(0.1)632,热处理对其硬度和耐磨性有明显的影响,二者分别在经300℃×1h和500℃×1h热处理后达到峰值。     

铝硅合金表面复合化学镀(Ni-B)-SiC的研究

研究了在铝合金(LG12)表面上复合化学镀(Ni-B)-SiC镀层工艺,对影响镀层镀速的几大因素进行了探讨,确定在铝硅合金上复合化学镀(Ni-B)-SiC的最佳工艺及相关参数.同时对该工艺下获得的复合镀层结构性能进行了研究.结果表明,分散相SiC的嵌入基本没有改变Ni-B基质合金原有的非晶结构.450℃热处理后,复合镀层向晶体结构转变,镀层硬度值HV14737,达到最大.     

Microstructure evolution of cobalt coating electroless plated on SiC whisker during electroless plating and heat treatment

SiC_w/Co nanocomposite particles were prepared by electroless plating cobalt on SiC whiskers and the microstructure evolution of the plated coating was investigated by SEM and XRD. SEM images show that growth occurs on the surface of the clusters at the initial stage; as they grow larger, the clusters converge to form a continuous coating, which is actually stacking of cobalt clusters. After heat treated at 500 °C in a hydrogen atmosphere, the cobalt coating transforms from an amorphous to a crystalline state. The thermal stability of SiC_w/Co composite is low because of the weak bonding between the substrate and the cobalt coating. The continuous coating aggregates to clusters through surface diffusion during heat treatment.     

Nanocrystalline electroless nickel poly-alloy deposition: incorporation of W and Mo

Autocatalytic quaternary Ni–W–Mo–P films were prepared using alkaline citrate based baths and compared with binary Ni–P and ternary Ni–W–P, Ni–Mo–P coatings. Energy dispersive X-ray analysis showed that the binary Ni–P deposit contained 12·2 wt-%P. Codeposition of tungsten in Ni–P matrix resulted in ternary Ni–W–P with 4·1 wt-%P and 5·2 wt-%W. Incorporation of molybdenum led to a ternary Ni–Mo–P deposit containing 4·1 wt-%Mo and 11·2 wt-%P. Presence of both sodium tungstate and sodium molybdate in the basic bath resulted in a quaternary coating with 3·6 wt-%W, 6·7 wt-%Mo and 2·5 wt-%P. X-ray diffraction patterns of all the deposits revealed a single peak for Ni (1 1 1). The quaternary alloy exhibited a sharper peak showing the more crystalline nature of the deposit. Field emission scanning electron microscopy studies of the deposits showed the presence of smooth nodules for ternary deposits, but coarse and well defined nodules for quaternary deposits. Phase transformation behaviour of the ternary Ni–W–P deposit revealed a single exothermic peak at 440°C. However, ternary Ni–Mo–P deposit exhibited a split type high temperature peak at 397 and 461°C and the quaternary Ni–W–Mo–P deposit showed a single high temperature peak at 485°C. Microhardness measurements showed that the quaternary Ni–W–Mo–P deposit exhibited increased hardness of 920 HV(50 gf) when heat treated for 1 h at 400°C.     

Microstructural characterisation and corrosion behaviour of electroless Ni–W–P deposits of mixed nanocrystalline/amorphous structures

Abstract

An investigation has been undertaken of the influence of the mixed nanocrystalline and amorphous microstructure on the corrosion behaviour of electroless Ni–5·5W–6·5P (wt-%) deposits on steel substrates. The effects of annealing temperature on microstructure evolution were investigated. The corrosion behaviour of the deposits was evaluated by potentiodynamic polarisation in 0·5M H₂SO₄ solution and EIS measurements in 3·5%NaCl solution. Relationships between the microstructure and corrosion mechanisms of the as plated and the annealed deposits were considered by reference to microstructural information, including degree of crystallisation, grain sizes of both nickel and Ni₃P phases, porosity development, microstrains and residual stresses.     

A study on the electroless Ni-P deposition on WE43 magnesium alloy

In this paper an attempt has been made to understand the mechanism of the deposition process of an electroless Ni-P (EN) coating on WE43 magnesium alloy. Also a number of properties concerning the deposited coatings have been reviewed. The results show that the starting microstructure of the alloy consists of a primary α phase together with some eutectic β phase at triple points and along with some grain boundaries. Microstructural studies reveal an uneven distribution of alloying elements in the phases and they are predominantly segregated to the eutectic β phase. This phenomenon can result in galvanic coupling between eutectic β and primary α phases. Detailed studies prove that the replacement reaction takes place at the early stages of coating, and is followed by the autocatalytic reaction at the next stages of deposition.The X-ray diffraction patterns of primitive coatings show a broad peak around 2θ of 45°, which is an indication of an amorphous or an extremely fine crystalline structure. Annealing at 400 °C for an hour led the nature of deposits to be changed to crystalline phases of Ni, Ni₃P, and NiP₃. Microhardness values of coatings are considerably higher than those of the bare substrate. These further increase when they are annealed at 400 °C for 1 h. Electrochemical polarization curves and calculated corrosion values reveal higher corrosion potential (E_corr) for the coating than for the bare substrate. This decreases again when the coating is annealed at 400 °C for 1 h.