去Co深度及薄膜厚度对金刚石薄膜-硬质合金附着力的影响

金刚石薄膜与基体的附着力是影响CVD金刚石薄膜涂层刀具使用寿命的关键因素,沉积金刚石薄膜的膜-基附着力主要受硬质合金基体表面Co含量的影响。本文通过控制酸碱两步法中的酸处理时间及薄膜沉积时间,利用扫描电子显微镜、能谱仪、拉曼光谱仪、划痕测试仪等对样品进行分析检测,研究基体去Co深度及薄膜沉积厚度对金刚石薄膜的膜-基附着力的影响。结果表明:随着去Co深度的增加,膜-基附着力先增后降,但薄膜表面和截面形貌无明显变化,表明薄膜形貌主要受沉积参数影响;随着薄膜厚度增加,薄膜晶粒变大,膜-基附着力先增高后降低。去Co深度为7.1μm,薄膜厚度为19.5μm时所得薄膜的膜-基附着力最高,达到88.82 N。     

高压输电耐张线夹用铝在中性溶液中的交流腐蚀行为

目的研究高压输电耐张线夹用铝在0.1 mol/L的中性Na2SO4溶液中的交流腐蚀行为。方法在耐张线夹端部截取块状腐蚀试样并包覆、打磨、清洗,利用自制设备测量试样在交变电流腐蚀作用下的Tafel曲线、交流阻抗谱和腐蚀速率,采用扫描电子显微镜分析微观腐蚀形貌,采用X射线衍射仪、能谱仪和X射线光电子能谱仪对腐蚀区元素及物相进行分析。结果交变电流密度为0~40 A/m2时,Tafel曲线负向移动;50 A/m2时,发生逆转,曲线正向移动;随交变电流密度增加,交流阻抗谱Nyquist图由单弧逐渐变为双弧,出现Warburg阻抗,Bode-Phaze图由单峰逐渐变为双峰;表面出现较多的点蚀坑和层状脱落痕迹;腐蚀产物为Al(OH)3和Al2O3。结论交变电流作用下试样的腐蚀倾向加深,腐蚀表面具有较多的空洞,垂直腐蚀和平行腐蚀交替进行,呈现层状脱落方式向基体演进,腐蚀产物与一般铝腐蚀产物相同,均为Al(OH)3和Al2O3,腐蚀速率在交变电流密度低于50 A/m2时相对较低,高于50 A/m2时大幅提高。     

钢铁表面电弧喷涂耐蚀铝涂层性能的研究

使用电弧喷涂技术在经过喷砂处理的Q235钢板喷涂厚度约为200μm的纯铝涂层,使用聚氨酯清漆对涂层进行封孔处理。通过金相组织分析试验、电化学测试以及中性盐雾试验研究了涂层的耐蚀性。结果表明:喷涂涂层的结构致密、成分均匀,涂层和基体材料结合情况良好。对涂层进行封孔处理后,腐蚀速度显著下降,试样的耐蚀性得到了极大改善。对封孔涂层进行120 h的中性盐雾试验,未发现明显腐蚀痕迹,涂层的耐盐雾腐蚀性良好。     

20G钢表面制备耐熔融铝硅合金腐蚀涂层的研究

太阳能热发电中,熔融铝硅合金储能材料会对换热管造成一定的腐蚀,为了延长换热管的使用寿命,在其表面制备了C1,C2和C3三种涂层,并对三种涂层的抗热震性能、附着力和耐熔融铝硅合金腐蚀性能进行了研究。结果发现:三种涂层具有较好的抗热震性能和附着力,在经过1 080h熔融铝硅合金腐蚀试验后发现,C3涂层具有最好的耐腐蚀能力,涂覆C3涂层的20G钢基体的腐蚀层厚度,相对于无涂层20G钢基体降低了93.69%。     

纳米封孔7Cr13电弧喷涂涂层的组织与耐腐蚀性

采用电弧喷涂工艺在基体Q235钢上喷涂了厚度约为150μm的7Cr13涂层,并采用3种封孔工艺对涂层进行封孔处理,封孔剂采用添加不同含量的纳米Al2O3异丙醇溶液的有机硅透明树脂.用乙酸盐雾腐蚀、全浸泡腐蚀以及电化学腐蚀检测了7Cr13涂层与对比材料镀铬层的耐腐蚀性能.结合扫描电镜、光学显微镜对腐蚀前后试样的表面形貌进行了观察和对比.结果表明,涂层呈层状结构,涂层封孔后孔隙率明显降低,涂层结合强度为47 MPa,远高于镀铬层,封孔涂层的耐腐蚀性明显优于未封孔涂层,纳米封孔7Cr13涂层的耐腐蚀性能优于镀铬层.     

基体激光淬火对镀铬层界面剪切强度的影响

针对激光淬火基体后再镀铬复合工艺提高镀铬身管寿命的实际工程问题，采用多裂纹拉伸技术证明该复合镀铬工艺可以提高界面剪切强度，并从材料学角度给予解释。离子冲击技术对界面强度的定性分析表明：激光淬火基体在消除铬层和基体之间过渡层的同时也提高了界面附近材料的强度。化学腐蚀去基体法研究表明，铬层界面材料强度的提高是晶粒细化的结果。因此得出激光淬火基体提高镀铬层界面剪切强度的原因是激光淬火消除了铬层和基体之间的过渡层和增强了界面附近材料的硬度和强度。     

铝硅涂层在1050℃下混合硫酸盐中的热腐蚀行为

采用粉末共渗法在镍基高温合金表面获得约为300μm厚的铝硅涂层,考察了其在1050℃下混合硫酸盐(Na2SO4+25%K2SO4)中的热腐蚀行为,较为系统地研究了其热腐蚀动力学行为及其机制、熔盐作用下氧化膜的生长与破坏过程和热腐蚀不同时间后的腐蚀产物等。结果表明,相对于已有铝硅涂层在高温条件下(850~980℃)热腐蚀的相关研究,其在1050℃超高温下混合硫酸盐中的热腐蚀更加严重,这与超高温下熔盐对保护性氧化膜的熔解作用更强密切相关。在本实验条件下,铝硅涂层在1050℃下混合硫酸盐中热腐蚀70 h后已趋于失效,当热腐蚀90 h时其腐蚀层深度已达约75μm;此时,不仅涂层中Al和Ni直接与熔盐相互作用,而且Cr、Si也参与了与熔盐的反应,同时高温合金基体中的Ti也已扩散至表面。     

等径角挤压制备的超细晶Al-5%Cu合金块材的腐蚀行为

采用全浸泡腐蚀和电化学腐蚀研究等径角挤压制备的超细晶铝铜合金块材在氯化钠溶液中的腐蚀行为。结果表明:超细晶铝铜合金中基体相α(Al)晶粒细小(为200～300nm);铸态组织中网状θ相(Al2Cu)破碎、细化成10μm左右的颗粒并均匀分布于形变α(Al)基体上;形变细化提高铝铜合金在氯化钠介质中的耐蚀性能,表现出全浸泡腐蚀中更轻的腐蚀程度、电化学测试中更大的极化电阻、更正的自腐蚀电位和点蚀电位、更小的腐蚀电流密度。     

管路衬盘裂纹失效分析

针对管道衬盘裂纹问题,利用有限元分析方式对其受载进行强度校核,并通过化学成分、硬度、宏观和显微组织等对其裂纹产生的原因进行分析。结果表明,坯件加工不当和装配过紧造成组织表面氧化防护层破坏,暴露出来的铝基体不断与管道内流体发生电化学腐蚀反应,同时零件未经任何热处理工艺,内部晶粒组织粗大位错密度较低,对裂纹扩展阻碍有限,最终在长期交变载荷下微裂纹不断扩展,造成最终的疲劳腐蚀失效。     

镍铝青铜9442#合金及其冷喷涂涂层磨蚀行为

采用冷喷涂技术在镍铝青铜9442合金上制备了较为致密,厚度约300μm的镍铝青铜涂层,使用SEM、XRD、XPS、电化学工作站、磨蚀试验机观察并测试了镍铝青铜合金与涂层的组织形貌、电化学行为与磨蚀性能。结果表明：电化学腐蚀后基体发生了晶间腐蚀和选相腐蚀,涂层被腐蚀后颗粒上出现微孔和裂纹;磨蚀过程中存在着摩擦与钝化的协同作用以及摩擦促进阳极溶解的过程;相比于静态条件下,涂层与基体在磨蚀条件下测得的自腐蚀电位有大幅度下降,自腐蚀电流均提高了一个数量级,涂层与基体耐腐蚀性能变差;相比于干摩擦过程,磨蚀过程中涂层与基体的摩擦系数均有较大提高,减磨性能变差。     

冷轧板带材切边圆盘剪侧向间隙及其精度的探讨

通过对切边圆盘剪侧向间隙调整精度及可靠性问题的分析,提出基于上、下刀盘端面跳动及上、下刀轴空间平行度的关键零件形位公差设计方法,对隔环、刀盘、刀轴轴肩及机架等零件形位公差进行了设计计算,保证了高精度切边圆盘剪侧向间隙调整精度及侧向间隙的可靠性。     

高边缘防腐蚀电泳漆的应用

目的提高零部件的边缘腐蚀。方法选择具有高边缘防腐电泳漆,该电泳漆具有良好的疏水性,添加微凝胶助剂可以控制涂膜流动,抑制电泳涂漆在烘干固化时的缩边现象,增加工件边缘尤其锐边和焊接部位的漆膜厚度和涂膜覆盖率,耐盐雾腐蚀性能得到显著提升。同时选择合理的涂装工艺,重点考察刀片腐蚀、铸造件、热板、酸洗板和冷板等不同材质工件边缘、棱角和焊接部位的耐腐蚀性能。结果通过对添加微凝胶高边缘防腐蚀电泳漆的应用,电泳漆阳离子树脂疏水性体系的设计和特殊微凝胶技术改进提升,刀片腐蚀达到240 h,铸造件达到480 h,工件可以达到1000 h盐雾试验单边腐蚀≤2 mm,完全满足汽车零部件防腐蚀性能的要求。结论选择合理的电泳涂装工艺和加强生产现场涂装过程管理控制,在热板、酸洗板及冷板等不同材质的材料上,高边缘防腐蚀电泳漆耐盐雾腐蚀性能可达1000 h以上,完全可以满足各种工件防腐蚀性能的要求。     

Electron Microscopy of Paint Films

Electron microscopy has been extensively applied to pigments, and to varnish and paint films. Some of the techniques used in preparing suitable specimens are described, with examples of their application to the examination of paint surfaces and their changes on ageing and weathering (including some effects of atmospheric pollution), the distribution of pigment particles within paint films and the relationships between paint and substrate and between successive paint coats.     

门头道密封用3M压敏胶粘带脱胶分析

车门头道密封条脱胶，不仅影响车间生产效率，还可能由于售后发生漏水引起顾客抱怨。为研究其脱胶原因，从胶带本身粘接性能、胶带与粘接表面发生作用时间、粘接表面能及清洁、车门内板与侧框外板间隙及头道密封条压缩力、头道密封条安装工艺等5个方面，对车门头道密封条脱胶失效进行探讨。结果表明:粘接部件表面是否清洁及胶带表面是否获得足够的压力是影响脱胶的主要因素，应该保证胶带横截面上获得100%在10 N以上、80%在20 N以上压力，被粘接部件表面清洁且表面能高于40 mN/m，其中极性组分高于4 mN/m，胶带与粘接部件作用时间不低于40 min，且在此期间保证胶带不会受到明显的外部剪切，压敏胶与车身油漆具有优异的粘接性能。     

等离子表面处理提高密封条漆面粘接稳定性的试验研究

针对频发的车门密封条脱胶问题,通过在不同工况下的浮辊剥离实验,研究密封条丙烯酸泡棉胶在漆面的粘接行为。经70 ℃加热5 min,丙烯酸泡棉胶带在2K清漆表面的粘接力由40 N/cm衰减至5 N/cm以下,表明在高温应力条件下,胶带在2K清漆表面存在较高的脱胶风险。在不同工艺参数下采用等离子处理对车身油漆进行粘接改性,并通过表面能测试和浮辊剥离实验,对处理后车身油漆的粘接改性效果进行研究。结果表明:等离子表面处理可以有效提高密封条在漆面的粘接稳定性。在功率500 W、喷枪距离8 mm、处理速度100 mm/s的工艺下,车身油漆达到最优粘接改性效果;在此工艺参数下对清漆进行表面处理的样品在所有工况下均为内聚破坏;等离子预处理后的漆面在一周内均能保持粘接有效性。     

Tensile testing of free-standing Cu,Ag and Al thin films and Ag/Cu multilayers

Free standing polycrystalline thin films with a strong 〈111〉 texture were tested in uniaxial tension. Studied were electron-beam deposited Ag, Cu and Al films, and Ag/Cu multilayers consisting of alternating Ag and Cu layers of equal thickness, between 1.5 nm and 1.5 μm (bilayer repeat length, λ, between 3 nm and 3 μm). The films had a total thickness of about 3 μm. A thin polymeric two-dimensional diffraction grid was deposited on the film surface by microlithographic techniques. Strains were measured in situ from the relative displacements of two laser spots diffracted from the grid. The average values of the Young’s moduli, determined from hundreds of measurements, are 63 GPa for Ag, 102 GPa for Cu, 57 GPa for Al and 87.5 GPa for Ag/Cu multilayers. In all cases, these values are about 20% lower than those calculated from the literature data and, for the Ag/Cu multilayers, are independent of λ. No “supermodulus” effect was observed. The 20% reduction in modulus is most likely the result of incomplete cohesion (“microcracking”) of the grain boundaries. The ductility of the Ag/Cu multilayers decreases when λ is reduced. For λ<80 nm, the films are brittle at room temperature: they break without macroscopic plastic flow. For λ>80 nm, the yield stress increases with decreasing λ according to a Hall–Petch-type relation. No softening with decreasing grain size was observed even at the lowest values of λ.     

基于神经网络遗传算法的磁粒研磨TC4材料工艺参数优化

目的利用磁粒研磨光整加工技术提高TC4材料的表面质量,使用BP神经网络建立加工工艺参数和表面粗糙度之间的关系,使用遗传算法寻找最优工艺参数组合。方法使用双级雾化快凝法制备的金刚石磁性磨料对TC4材料工件进行L9(34)正交试验,借助Matlab软件建立结构为4-12-1的BP神经网络,根据正交试验结果训练BP神经网络,探究工艺参数主轴转速n、加工间隙δ、进给速率v、磨料粒径D和表面粗糙度Ra之间的关系。使用决定系数R2评判BP神经网络训练结果,基于训练好的BP神经网络使用遗传算法对工艺参数进行全局寻优。使用计算得到的优化工艺参数进行试验,并测量工件表面粗糙度,与计算得到的表面粗糙度做对比。结果BP神经网络的预测误差在1.5%以下,通过决定系数R2优化的模型可在训练样本较少的情况下进行有效可靠的预测。遗传算法优化的结果,在主轴转速为1021.26 r/min、加工间隙为1.52 mm、进给速率为1.04 mm/min、磨料粒径为197.91μm下,获得最佳表面粗糙度,为0.0951μm。使用调整后的工艺参数,在主轴转速为1020 r/min、加工间隙为1.50 mm、进给速率为1.0 mm/min、磨料粒径为196μm下,试验得到的表面粗糙度为0.093μm,与计算得到的最佳表面粗糙度误差为2.21%。结论采用磁粒研磨光整加工技术与寻优参数结合,可以有效提高TC4材料加工后的表面质量。     

Effects of SiC volume fraction and aluminum particulate size on interfacial reactions in SiC nanoparticulate reinforced aluminum matrix composites

The SiC nanoparticulate reinforced Al-3.0 wt.% Mg composites were fabricated by combining pressureless infiltration with ball-milling and cold-pressing technology at 700 °C for 2 h. The effects of SiC nanoparticulate volume fractions (6%, 10% and 14%) and Al particulate sizes (38 μm and 74 μm) on interfacial reactions were investigated by SEM, TEM and X-ray diffraction. The results show that the MgO at the interface between SiC nanoparticulate and molten Al can provide a barrier for the diffusion of Si, C and Al. Using Al particulate (74 μm) as raw material, the Al₄C₃ phase was not found in the composites containing 6 vol.% and 10 vol.% SiC, but presented in the composites containing 14 vol.% SiC. When SiC content up to 14 vol.%, the products of MgO around SiC nanoparticulate are not enough to provide effective protection from the reaction between SiC and molten Al, therefore the diffusion of Si, C and Al can take place to produce Al₄C₃ and Si phases. Using 38 μm Al particulate as raw material, the fine Al particulate possesses the high reaction activity and can easily be embedded into the gap among the big Mg particulate segregated at the interface, resulting in the appearance of exposure surface of SiCp to the Al and the forming of diffusion channels for the atomics C, Si and Al. So, the formations of Al₄C₃ and Si phases were occurred.     

Effect of current pulses on the drawing stress and properties of Cr17Ni6Mn3 and 4J42 alloys in the cold-drawing process

Current pulses (approximately 10³ A/mm² for about 20 μs) have been applied to the drawing process of Cr17Ni6Mn3 and 4J42 (42Ni–56Fe) alloyed wire, the drawing stress being found to be decreased significantly. Furthermore, the ultimate tensile strength σ_b was decreased and the elongation ratio δ (%) was increased with the application of the current pulses. In this experiment, the wire-drawing velocity of Cr17Ni6Mn3 was increased from 9 m/min to about 60 m/min, latter being the actual wire-drawing velocity employed in the factory. With the data of the magnetic properties of the Cr17Ni6Mn3, it was found that the saturated magnetization B_s and the residual magnetization B_r had decreased with the application of the current pulses. On the other hand, with the increase of the drawing speed, the decrease of the drawing stress had reduced, which accorded with the data of magnetic properties. Thus, the frequency of the current pulses should be increased with the increase of the wire-drawing velocity so as to ensure the electroplastic effect.     

Shear banding and recrystallization texture development in a multilayered Al alloy sheet produced by accumulative roll bonding

A commercial purity Al alloy and an Al–0.3 wt.% Sc alloy, the latter in either the supersaturated or artificially aged condition, were accumulative roll bonded to produce 0.5-mm-thick sheet consisting of multiple alternating layers of Al and Al(Sc). The deformation mechanism of these two combinations was strongly influenced by the relative hardening behaviour of the adjacent layers. For the Al/Al(Sc)_aged material, a higher magnitude of in-plane shear stress, well exceeding the flow stress of Al(Sc), was operative at the interface between layers. This resulted in through-thickness shear banding and a marked curvature of the layers in the RD–ND sections. Shear banding also resulted in a reduction in intensity of the rolling texture components and had a randomizing effect on the recrystallization texture of the Al layers. In both conditions, the Al(Sc) layers were resistant to recrystallization after extended annealing at 350 °C and produced a microstructure of recovered equiaxed grains ～0.5–0.8 μm in diameter.