复合电沉积过程中的界面调控和界面结合研究进展

复合电沉积是一种获得功能镀层的表面防护技术。概述了界面调控与界面结合对复合镀层性能的重要影响。分析了提高界面结合能力的主要机理与方法,即:通过基体表面改性,如增加基体表面粗糙度、提高反应活性、提供外延生长条件和形成预镀层或转化膜层等,增强镀层与基体之间的机械结合、化学键合作用,进而提高镀层与基体间的界面结合力;通过颗粒改性,包括颗粒表面清洁、修饰与吸附等,以改变颗粒微观结构形态和荷电状态,利用静电机制、空间位阻机制和电胶束空间等理论来增强颗粒与颗粒间的分散能力、颗粒与金属离子间结合能力和颗粒所受电化学作用力等,从而提高颗粒与镀层之间的异质相界面结合能力。鉴于镍基复合电沉积的重要性以及颗粒改性对提高其界面结合的关键作用,综述了其颗粒改性工艺研究和影响,包括细化镍基复合镀层晶粒、改变颗粒表面接触状态、增加颗粒沉积量与其对镍基复合镀层性能的影响。最后对复合电沉积的界面调控和界面结合研究做了总结,指出现阶段还存在的问题,并展望了复合电沉积技术在界面调控和界面结合方面的研究发展方向。     

镍的摩擦辅助喷射电沉积过程及沉积效率

分别使用传统喷射电沉积和摩擦辅助喷射电沉积技术制备一组不同沉积时间的镍沉积层,并采用非接触式表面三维形貌仪对其表面形貌进行观察,采用XRD分析沉积层的晶粒大小和织构随沉积时间的变化,用TEM观察沉积层组织机构的不同,通过沉积层的厚度分析对两种方法的沉积效率和稳定性进行比较。结果表明:传统喷射电沉积镍层随着沉积时间的增加表面逐渐变得粗糙,沉积时间由20 min增加至120 min时,粗糙度Ra值由212 nm增加至282 nm,而摩擦辅助喷射电沉积镍层可以始终保持光亮平整,Ra值由最初的228 nm逐渐减小,并最终稳定在171 nm左右;摩擦辅助装置的加入对喷射电沉积效率影响很小,但使沉积的均匀性和稳定性得以提高;同时,该装置细化晶粒,使平均晶粒大小由15.6 nm减少至10.9 nm。     

激光重熔喷射电沉积纳米晶镍涂层微观结构

采用喷射电沉积法在45钢基体表面制备了纳米晶镍涂层,研究了激光重熔工艺对组织的影响.用扫描电镜、X射线衍射仪和显微硬度计分析了涂层表面形貌、微观结构和显微硬度.结果表明,在优化的工艺参数下,喷射电沉积制备的镍涂层表面较平整、结合较致密,由平均尺寸为13.7 nm的纳米晶颗粒组成,但晶粒间仍有一定的间隙;经激光重熔后,熔融区内的晶粒尺寸明显减小,使涂层致密化程度得以提高并使涂层与基体由机械结合变为冶金结合,因此激光重熔处理后涂层的显微硬度明显提高.     

电沉积-水热合成法制备的生物陶瓷涂层与基体界面结合强度的研究

采用电沉积水热合成法和高温煅烧相结合的方法，制备了生物陶瓷涂层，研究了涂层与基体间过渡层的物相组成和界面结合强度。用X射线(XRD)、扫描电镜(SEM)和粘接拉伸法进行分析。结果表明：水热合成后，界面结合强度较低，为7．04MPa。在空气中煅烧，700℃以下时，界面出现极薄TiO2层，同时随着煅烧温度的升高，界面结合强度提高；800℃以上时，由于厚而疏松过渡层TiN的出现，界面结合强度反而下降。为获取对骨生长有利的HAP β-Ca3(PO4)2双相结构，且界面结合强度高的涂层材料，将原始试样用NaOH碱液处理并进行电沉积水热合成，在氩气中900℃煅烧后，过渡层为薄且致密的TiO2层，界面结合强度高达22．39MPa。     

电沉积泡沫镍的DTR控制研究

研究电解液的组成和电沉积过程对电流密度的影响,指出决定厚尺度泡沫镍沉积厚度比(DTR)的决定因素是电流密度的控制,而电解液的电导率及主盐浓度也有重要影响.     

脉冲电沉积纳米晶体镍腐蚀特性的研究

采用脉冲电沉积工艺制备纳米晶体镍和普通微晶镍，用浸泡法和电化学极化法研究了电解镍板、普通微晶镍和纳米晶体镍在3．5％NaCl溶液及10％HCl溶液中的腐蚀行为。结果表明，在NaCl溶液中，这3种晶体镍的耐蚀性能均较好，但纳米晶体镍中的晶界体积分数增加，最容易被腐蚀。在HCl溶液中，这3种镍仍具有较好的耐蚀性，但纳米晶体镍耐腐蚀能力最低。     

热镀锌铁合金钢板冲压成形过程表面特性研究

热镀锌铁合金钢板在冲压过程中经常出现锌层的粉化和剥落等质量缺陷,加大了质量控制的难度.本文分析了不同预变形条件下热镀锌铁合金镀层的表面形貌和断面金相的演化,同时研究了正压力对摩擦系数的影响.结果表明:锌铁合金层镀层裂纹的萌生和发展是导致锌层粉化的根本原因.随着正压力的增大,锌铁合金钢板的摩擦系数明显降低,但当压力较大时降幅明显放缓.     

泡沫镍制备中脉冲电沉积镍研究

研究了泡沫镍制备过程中脉冲电沉积镍工艺参数(电流密度、脉冲频率、占空比)对沉积速率、镍沉积层的晶体结构和微观形貌的影响.最佳脉冲电沉积工艺参数为:电流密度2.0 A/dm2,脉冲频率1000 Hz,占空比1∶5.此时获得的镍沉积层结构平整,粒度分布均匀,晶体结构完整.     

机械研磨对电沉积镍镀层晶粒生长过程的影响

在Watt镀液中加入玻璃球,玻璃球以不同频率垂直撞击试样表面形成机械研磨.考察了震荡频率和球直径对镍镀层晶粒细化的影响以及机械研磨对晶粒生长的影响.SEM表面观察表明,机械研磨改变了镀层晶粒的生长方式,使镀层晶粒明显细化,镀层表面光滑.在电沉积过程中施加机械研磨,玻璃球的撞击会在镀层表面产生宏观和微观缺陷,增加形核中心,提高形核速率;玻璃球撞击晶粒尖端,使得镀层表面变得平整,有利于电力线均匀分布,促进形核,避免了晶粒不均匀长大.     

电沉积非晶态镍磷合金晶化过程研究

利用差示扫描量热仪(DSC)和X射线衍射仪(XRD)研究了w(P)=12.3%的电沉积非晶态镍磷合金镀层的晶化过程.结果表明,w(P)=12.3%的非晶态镍磷合金镀层的DSC曲线具有4个放热峰:镀层在260℃热处理时仍保持非晶结构;在270、290、300和320℃热处理后,析出亚稳相Ni12P5和Ni5P2;在360℃热处理后,亚稳相Ni12P5减少,亚稳相Ni5P2消失,析出Ni3P和Ni;镀层经420℃热处理后,亚稳相Ni12P5和Ni5P2完全消失,晶化产物为Ni3P和Ni.     

Computation of deformation-induced textures in electrodeposited nickel coating

The deformation-induced textures in electrodeposited nickel coating were numerically studied. The finite element method （FEM） for polycrystalline was developed based on Taylor model. Then the deformation-induced textures in electrodeposited nickel coating with initial random and lamellar texture were simulated under tensile load. It is found that the initial textures significantly influence the deformation-induced textures. For nickel coating with the initial random textures, when （he tensile strain is about 40%, there are some lamellar textures. For nickel coating with the initial lamellar textures, the lamellar texture is more intensity with the increase of the tensile strain. With the increase of the tensile strain in the coating, there are more pronounced element distortion and a more inhomogeneous deformation. Due to the different crystal orientations, the grain-scale roughness is observed. With increasing tensile strain in the coating, the surface grain-scale roughness increases on the flee surface. The surface roughness of the coating with initial random texture is lower than that with the initial lamellar texture.     

Forming limit of electrodeposited nickel coating in the left region

A uniform nickel (Ni) coating was bilaterally electrodeposited on the low-carbon steel substrate for the application of advanced battery shells. Its forming limit was investigated by Hill localized necking theory coupled with finite element simulation and scanning electron microscopy. The effective stress and effective strain in the Ni coating and steel substrate are deduced using Hill’s anisotropic yield function. The localized necking condition is derived by sandwich sheet analysis, and the forming limit strains are obtained by solving the nonlinear equation of the localized necking condition. Extensive calculations are carried out using the proposed model. This study exhibits the nickel coating thickness and the normal anisotropic coefficients of the coating and substrate have little influence on the forming limit curve (FLC) in the left region of the coated sheet, but the strain hardening exponents of the coating and substrate have much effect on it. The calculated result matches well with the measured data in uniaxial tension. This investigation is useful for the preparation of the electrodeposited Ni coating and helpful for the forming operation of the battery shells.     

Effect of tension deformation on microstructure and mechanism of electrodeposited nickel coating

Nickel coating deposits with better ductility on a lower carbon steel sheet were produced by electrodeposition method and the electrodeposited nickel coating was deformed with the strain of 10%. Then the surface morphology, the deformation texture and the mechanical properties were analyzed by scanning electron microscopy （SEM）, X-ray diffractometry （XRD） and nano-indentation measurement, respectively. The principle of nano-indentation to measure the hardness and elastic modulus of nickel coating was introduced. The relation curves of the load and displacement were obtained, including the original electrodeposited samples and the samples under tension. The results show that： 1） there are only two main texture components Ni （111） and Ni （200） in the nickel coating, and no new texture component is found due to the elongation; 2） after tensile deformation in the coating, the surface roughness increases and the microcrack is found; 3） The hardness and the elastic modulus decrease after tensile deformation; and 4） for the original electrodeposited sample, the indentation depths change with the load, the hardness and the elastic modulus decrease with the increase of the depth. In addition, the investigation of creep shows that the value of creep increases when the tensile strain ε〉 10%.     

镍基合金复合钢板的焊接

环化塔预热器壳体的设计材料是Hastelloy C-276、Monel 400两种镍基合金复合不锈钢板,焊接是制造这台设备的关键技术.通过分析镍基合金复合钢板的焊接特点,指出镍基合金复合钢板焊接的关键是控制基层根部焊接时,焊缝金属中不要熔入复层合金成分;复层堆焊后的合金成分接近或达到焊材的化学成分,满足耐蚀要求.采用台阶式坡口形式,是避免根部焊缝金属互熔的最好措施;控制焊接线能量的多层焊是保证堆焊复层耐蚀性的关键.     

Formability of aluminum-silicon coated boron steel in hot stamping process

Flow behavior of the Al-Si coated boron steel was investigated with Gleeble-3500, in comparison with the uncoated one. Effect of deformation conditions on the coating integrity was characterized by optical microscopy. Facture surfaces of the coated steels were inspected under SEM. Experimental results indicate that the ultimate tensile strength and ductility of the Al-Si coated boron steel are lower than those of the uncoated steel under test conditions. Extensive cracks occur in the coating after tensile tests; the width and density of cracks are sensitive to the deformation temperatures and strain rates. The bare substrate exposed between the separate coating segments is oxidized. Appearance of the oxide degrades the Al-Si coating adhesion. Remarkable difference between formability of the coating layer and the substrate is confirmed. The formability of the Al-Si coating could be optimized by controlling the phase transformation of the ductile Fe-rich intermetallic compounds within it during the austenization.     

奥氏体化过程中热冲压钢Al-Si镀层的组织演化

利用差示扫描量热仪、场发射电子探针和激光共聚焦显微镜研究了22MnB5热冲压钢奥氏体化过程中Al-Si镀层的组织演化。镀层板升温过程中,Al-Si镀层在570 ℃左右熔化;由于温度较低,Al、Fe、Si原子的扩散受到Fe₂SiAl₇阻挡。当温度升到610 ℃左右时,扩散到镀层的Al原子增多,使得Fe₂Al₅进一步生长;Si原子向基体和镀层外表面扩散,由于Fe₂Al₅溶解Si原子能力弱,因此在Fe₂Al₅晶界处形成一层沉淀物FeSiAl₂,其余的Si原子就扩散在镀层表面形成Fe₂SiAl₇。750 ℃时,Al原子扩散到基体中形成了Fe₃Al;镀层中的Fe原子增加使Fe₂Al₅和FeAl₂不断生长;由于Fe₂Al₅和FeAl₂相中Si原子的溶解度低,因此会在晶界处形成Fe₃SiAl₅沉淀物;与Fe₂Al₅、Fe₃SiAl₅、Fe₃Al相比,FeAl₂相的生长速度更快,所占Al-Si镀层整体体积最大,这是因为FeAl₂正交晶格中沿c轴的高空位率(30%)导致了FeAl₂相的生长动力学更强。     

超高强度热轧钢板冷冲压开裂原因及分析

针对屈服强度700 MPa级超高强度热轧钢板冷冲压时出现开裂现象,对其剪切加工方式以及剪切材料端部进行了研究。结果表明,剪切端局部加工硬化以及大量残留的微裂纹扩展是700 MPa级热轧超高强钢板冲压产生开裂的主要原因。通过边缘局部回火或局部修磨去除裂纹源,可避免出现开裂或者降低开裂几率。     

Cup-drawing formation of steel sheet with nickel coating by finite element method

The finite element method （FEM） simulation of deep-drawing of steel sheet with nickel coating based on the solid element and dynamic explicit method was reported. Penalty function method was used to treat the contact algorithm. The friction between the punch and coating sheet was based on a Coulomb formulation. The combination of coating and substrate was defined as tied with failure contact. The results of the simulation illustrate that the steel sheet and the nickel coating do not delaminate at the interface. The stress field of the nickel coating is more complicated thala that of the steel substrate. Furthermore, it is found that the punch-nose radius is the most unsubstantial part for the intensity of the entire deep-drawing part and the thinnest part, it is a dangerous zone for the break. At this zone, the thickness thinning of the steel sheet and the nickel coating are up to 4.8% and 6.7%, respectively. Meanwhile, it is found that the curve of the variable blankholder force （VBHF） designed can improve the formability of sheet.     

氧化铝涂层垂直裂纹对热载荷下界面失效的影响

目的探索氧化铝/铝在热载荷作用下的界面失效机理。方法基于内聚力有限元模型,预测热载荷下铝基氧化铝涂层材料界面处的残余热应力,并系统研究其失效过程。重点考虑涂层厚度、热载荷大小、预制涂层垂直裂纹密度对界面处应力场和界面损伤失效的影响,并同实验进行对比。结果试验和模拟结果都发现,加热到300℃冷却后,界面未产生平行裂纹,而加热到400℃冷却后,界面出现平行裂纹。涂层无裂纹缺陷时,界面处剪应力呈单曲线余弦分布,而有预制裂纹时,界面处的剪应力呈双曲线余弦分布。随着热载荷的增大,界面最大剪应力值由两端向界面中心处迁移。相比涂层有裂纹的情况,界面在涂层无裂纹时平均正应力最小。实际制备的氧化铝涂层不可能完美无裂纹缺陷,在考虑涂层有裂纹缺陷时,涂层裂纹密度为4 mm~(-1)时平均所受正应力较小,且界面只有拉应力作用,不容易产生脱层缺陷。结论存在特定的最佳临界预制垂直裂纹密度值,使得热载荷下界面损伤最小。有限元模拟结果也显示,相同热载荷和相同裂纹密度下,涂层越厚,对界面的防护力也越强。     

Evolution of deformation-induced texture and surface microstructure of nickel coating under deep cup-drawing process

The deformation texture and surface microstructure of nickel coating induced by deep cup-drawing were studied by X-ray diffractometry and SEM. The steel sheet with nickel coating was firstly punched to designed degree of cup shapes. Then the texture of the coating was determined by XRD and the surface microstructure was observed by SEM. The results indicate that, the nickel coating material includes three kinds of textures, i.e. Ni （111）, Ni （200） and Ni （220）. After cup-＆awing deformation, there doesn＇t appear new texture component for nickel coatings but the change of the intensity of the deformation textures. In the cup-deformation process, the two kinds of main textures Ni （111） and Ni （200） increase in the first and second cup-drawing procedures and then reduce quickly in the third and fourth drawing procedure. However, for the Ni （220） texture, it always increases in whole cup-drawing procedures. With the increase in the drawing, there are some cracks to be found, but not delamination. This shows that nickel coating and the substrate have a good combinable performance.