化铣保护涂料的选择

为提高铝合金零件的化学铣切质量,拟采用新型化学铣切保护涂料用于生产,对三种化铣保护涂料AC-850、TP-1020-1、HX-150漆层进行常规性能试验,重点对三种化铣保护涂料的刻型检查、浸蚀比、抗蚀性试验方法进行研究,并选定适宜的化学铣切保护涂料并掌握其施工工艺。     

SEBS新型可剥性化铣保护涂料的研制

国内化铣保护涂料市场主要被国外产品所占据,进口涂料产品价格昂贵。为此,选用氢化SBS树脂(SEBS)为主成膜物,辅以酚醛树脂进行物理改性,再配以液体石蜡、气相二氧化硅、滑石粉、消泡剂等辅助材料,制得了一种可剥性化铣保护涂料,并与美国同类产品进行了性能对比。结果表明:该涂料具有浸蚀比小、刻线平直、漆膜硬度大、化铣后变色小、漆膜外观好、可重复利用性强等优点,满足化学铣切工艺的要求,与美国同类产品的性能基本相当。     

化学铣切技术在钛合金钣焊机匣制造上的应用

大型钛合金化学铣切技术是我国航空领域正在兴起的一种新的加工技术．本文对化学铣切技术的优点、影响化铣技术的因素等方面研究现状进行了综合评述。‘;     

化学铣切铝合金的疲劳性能

铝合金的化学铣切已经成为航空与航天工业零件成形的可靠加工方法,尤其是在加工飞机蒙皮时要比用传统的机械加工方法优越得多.但化学铣切在一定程度上会降低材料的疲劳寿命,是由于存在于金属板材表面抗疲劳的残余压应力在化铣过程中释放后造成的.因此有必要考虑化铣工艺对飞机疲劳寿命的影响.通过对化学铣切的2024-T3包铝疲劳性能的研究,以及对大型薄形试片疲劳试验方法的探讨,确定该化学铣切工艺完全能满足民用飞机疲劳寿命的要求.     

2197铝锂合金碱性化铣液中Al3+浓度对化铣表面质量的影响

铝锂合金有望在航空航天领域广泛使用,常对其进行化铣加工.目前,尚未见关于化铣液中Al3+如何影响铝锂合金化铣表面质量的详细报道.研究了碱性化铣液中Al3+浓度对2197铝锂合金化铣加工速率、表面粗糙度、浸蚀比及加工精度等的影响.结果表明:随着化铣液中Al3+浓度增加,化铣速率不断下降,当化铣速率低于20 μm/min时,槽液失效;化铣试样表面粗糙度和浸蚀比均随Al3+浓度增加呈不断下降趋势,Al3+浓度过低或过高均不利于化铣;A13+浓度的增加对加工精度的影响不大,铝锂合金的初始化铣液中含有一定量的Al3+浓度对化铣有利;综合考虑,化铣时适宜的Al3+浓度为20～60 g/L.     

玻璃纤维基强酸性离子交换纤维的制备

以过氧化苯甲酰为引发刑,将苯乙烯-二乙烯苯交联低聚物包覆在玻璃纤维表面,得到聚(苯乙烯-二乙烯苯)包覆纤维,然后用浓硫酸将聚(苯乙烯-二乙烯苯)包覆纤维磺化,制备强酸性离子交换纤维.研究了反应液固比、反应时间及反应温度对离子交换容量的影响,并用红外光谱加以表征.结果表明:二乙烯苯含量为5%的聚(苯乙烯-二乙烯苯)包覆纤维,在液固比1:4,温度100℃下磺化反应12h,可得到离子交换容量为4.08mmoL/(g树脂)的强酸性离子交换纤维.     

苯乙烯改性醇酸树脂热变色涂料的研究

为了克服醇酸树脂涂膜干燥缓慢,硬度低,耐水性、耐候性不佳等缺点,利用苯乙烯对醇酸树脂进行改性,制备出干燥快,硬度高,耐水性、耐腐蚀性、耐候性好的苯乙烯改性醇酸树脂,再将热变色材料分散于苯乙烯改性醇酸树脂中,制备出苯乙烯改性醇酸树脂热变色涂料.结果表明:所得到的苯乙烯改性醇酸树脂热变色涂料的干燥快,硬度高,耐水性、耐腐蚀及耐候性好,热变色效果明显.     

氯丁橡胶剥漆在局部电镀中的应用

１ 前 言 我所在电镀生产中采用涂料绝缘保护法进行局部绝缘。局部绝缘所用涂料又称屏蔽涂料、保护涂料或可剥性涂料。可剥性涂料在局部电镀工艺过程中尽管起暂时保护作用，但是对局部电镀工艺过程的完成是至关重要的。因此，世界各国对可剥性涂料及其配套产品的研究工作给予了极大的关注　。目前，国内使用的可剥性涂料主要有：用于铝合金的氯丁橡胶可剥漆和Ｊ６４－３２黑色丁苯橡胶可剥漆、用于钛合金与不锈钢的丁基橡胶可剥漆和双组分氯磺化聚乙烯可剥漆、Ｇ６４－１过氯乙烯可剥漆、低毒性的水分散型乳胶化铣保护涂料和光敏型化铣保护…     

钛合金化铣夹具的研究

钛合金以其优越的性能,在航空发动机中应用越来越广泛,但其机械加工性能差制约其在航空发动机中实际应用。其中薄壁筒体钛合金零件最为难加工,以往采用机械加工方法容易造成零件变形,无法保证零件图纸尺寸要求。为保证零件质量,采用化铣的加工方法,而化铣夹具性能直接影响零件化铣质量。通过对零件设计图纸及其化铣工艺的深入分析,研究出一套科学的、可行的钛合金化铣夹具结构设计方法。解决了零件在化铣过程之中,化铣夹具主体材料在含有硝酸和氢氟酸的槽液中不被腐蚀以及化铣夹具能够带动零件匀速转动的问题。该钛合金化铣夹具的成功应用,为今后此类零件的化铣夹具的设计提供了一定经验。     

GH4169高温合金化学铣切表面粗糙度的影响因素

为了满足生产对GH4169高温合金化学铣切加工表面粗糙度的要求,通过单因素试验研究了化铣液的主要成分和化铣工艺参数对GH4169高温合金表面粗糙度的影响。结果表明:随着化铣液中FeCl3和HNO3浓度的升高,表面粗糙度呈下降趋势;当化铣液温度高于50℃时,表面粗糙度在1.4μm以下;HCl,HF浓度均为200 mL/L时,表面粗糙度最小;添加剂SA和SN能够降低表面粗糙度和消除凹槽;随着化铣液中Ni2+浓度的增加,表面粗糙度也随之变大,当Ni2+浓度大于26.95 g/L时,表面粗糙度达到1.6μm以上,不符合加工要求;最佳化铣工艺为200～250 g/L FeCl3,200 mL/L HF,150 mL/L HNO3,200 mL/L HCl,0.2 g/L添加剂SA,0.5 mL/L添加剂SN,温度53℃,该工艺下化铣的GH4169高温合金表面质量良好,无凹槽、沟蚀,表面光洁,粗糙度小于1.6μm,符合生产要求。     

镀锌层钛溶胶钝化及其耐蚀性

为了进一步提高镀锌层的耐蚀性而又利于环保,配制了钛溶胶,并在镀锌层表面涂覆成膜。分析了钛溶胶钝化成膜机理,研究了钛酸四丁酯含量、钝化液pH值、钝化时间及钝化后热处理温度对钝化膜耐蚀性的影响,用扫描电镜(SEM)观察了钝化膜的微观形貌。结果表明:当钛酸四丁酯含量为12.5 mL/L,钝化液pH值1.3,钝化时间15 s,热处理温度40℃时,钝化膜具有较好的防护性能;镀锌层经钛溶胶钝化处理后,表面趋于致密,同时更加平整,有利于进一步提高镀锌层的防护性能。     

Coatings of Aluminide Intermetallic Compounds on Steel Utilizing a Hybrid Technique of Spraying and IR-Laser Fusion

Titanium aluminide coatings were produced using a hybrid technique of arc-spraying followed by IR-laser fusion in an argon atmosphere. A titanium coating free of oxides was deposited onto a low-alloy steel by DC-arc spraying in argon. Optimal laser irradiation conditions and the amount of preplaced aluminum powder on the sprayed titanium were determined to obtain a composite coating of TiAl₃+Al of 150 urn thickness. Metallurgical and mechanical properties were examined using acoustic emission. The oxidation resistance of the coating was excellent up to 1173 K because of a protective alumina layer. Growth of the TiAl₃interlayer by diffusion of aluminum into titanium improved the corrosion resistance. The intermetallic coadng showed microcracking at ambient temperature, but possessed capability for filling and healing of cracks with alumina and titanium nitride during high-temperature exposures. However, at temperatures higher than 1200 K, the oxidation performance decreased by diffusion of iron into the coating     

Failure of Centrifugal Chillers: Coating and Anode Location Problems

This article reports on the failure of two centrifugal chillers that were installed in a large building complex by the seaside. The carbon-steel divider plates of the failed chillers were perforated and severely corroded, although protective coating and cathodic protection had been applied. It was found that the ??protective?? coating was faulty as they contained the metallic pigment titanium, which is nobler than the underlying carbon steel. The location of the zinc anode on the chiller doors was also problematic. Suggestions for design improvement in protection against corrosion for such centrifugal chillers are proposed.     

Plasmachemical synthesis of coatings using a vacuum arc discharge

In this paper we discuss the issues of applying protective coatings on the copper anodes of powerful generator tubes. As a synthesized material due to its high operational properties was chosen titanium carbide obtained by sputtering a titanium cathode in benzene vapors. Scheme of a vacuum arc device used in this work and also the technological processes for the plasmachemical synthesis of coatings on complex shape anodes are described. For a correct choice of the technological parameters it was considered a model of penetration of the plasma flux into the hollow copper anode that was verified by experiments using a setup with a variable cavity diameter. On the emission spectrum of the discharge in the process of coating deposition shown in this work were recorded spectral lines corresponding to the atoms and ions of titanium and carbon ions. We investigated the distribution of elements across the thickness of the formed coating immediately after deposition and after annealing in vacuum, also the X‐ray diffraction pattern and a microsection for the obtained titanium carbide coating are presented. As a result of the work it can be noted that the described sequence of technological processes, subject to the control of plasma flux parameters, allows obtaining a high quality protective coating on parts of complex shape.     

Nanostructured Al2O3–TiO2 coatings for high-temperature protection of titanium alloy during ablation

Plasma-sprayed nanostructured Al₂O₃–13 wt.%TiO₂ coatings were successfully fabricated on titanium alloys (Ti–6Al–4V) using as-prepared feedstock. Ablation experiments for the titanium alloy samples with or without a coating were carried out using a Metco 9MB plasma gun. The microstructure, phase constituents and mechanical properties of the titanium alloys before and after ablation were investigated by scanning electron microscope (SEM), X-ray diffractometer (XRD) and Vickers hardness tester. The surface morphologies, cross-sectional microstructure and hardness of titanium alloys with coatings are similar before and after ablation. In contrast, the microstructure and mechanical properties of the titanium alloy without coating are significantly changed after ablation. The surface coating is found to serve as a protective coating during ablation.     

Fabrication and oxidation resistance of titanium carbide-coated carbon fibres by reacting titanium hydride with carbon fibres in molten salts

Using carbon fibres and titanium hydride as a reactive carbon source and a metal source, respectively, a protective titanium carbide (TiC) coating was formed on carbon fibres in molten salts, composed of LiCl-KCl-KF, at 750-950 °C. The structure and morphology of the TiC coatings were characterised by X-ray diffraction and scanning electron microscopy, respectively. The oxidation resistance of the TiC-coated carbon fibres was measured by thermogravimetric analysis. The results reveal that control of the coating thickness is very important for improvement of the oxidation resistance of TiC-coated carbon fibres. The oxidative weight loss initiation temperature for the TiC-coated carbon fibres increases significantly when an appropriate coating thickness is used. However, thicker coatings lead to a decrease of the carbon fibres' weight loss initiation temperature due to the formation of cracks in the coating. The TiC coating thickness on carbon fibres can be controlled by adjusting the reaction temperature and time of the molten salt synthesis.     

汽车用钛合金表面双辉等离子Mo合金化层的制备及其摩擦磨损性能

为了改善钛合金的表面摩擦磨损性能,采用双辉等离子合金化法在汽车用近β型钛合金(Ti-5Zn-3Sn)表面制备了Mo合金层,通过微观组织观察及硬度、摩擦系数、磨损率测试等考察了合金化层的形貌以及摩擦磨损性能.结果表明:钛合金表面等离子合金化后,呈现出银白色,表面形貌很不平整,粗糙度和致密性得到提高.钛合金Mo合金化层与基体之间结合很好,没有出现不可控的断层以及裂纹.随着合金化层的逐渐深入,Mo元素占比慢慢降低.在Mo元素固溶强化作用的影响之下,钛合金表面硬度得到明显提高,有效地改善了钛合金表面摩擦学性能.随着Mo合金化温度增加,合金化层的硬度明显增加.合金化后钛合金表面硬度高,受压屈服极限大,黏着效应小,摩擦系数小,磨损率明显降低.     

Surface characteristics and electrochemical corrosion behavior of a pre-anodized microarc oxidation coating on titanium alloy

A porous bioactive titania coating on biomedical β titanium alloy was prepared by pre-anodization followed by micro arc oxidation technology. The effects of pre-anodization on the phase constituent, morphology and electrochemical corrosion behavior of the microarc oxidation coating were investigated. The results show that pre-anodization has less influence on the phase constituent and the surface morphology of the microarc oxidation coating, but improves the inner layer density of the microarc oxidation coating. The decrease of plasma discharge strength due to the presence of the pre-anodized oxide film contributes to the formation of the compact inner layer. The pre-anodized microarc oxidation coating effectively inhibits the penetration of the electrolyte in 0.9% NaCl solution and thus increases the corrosion resistance of the coated titanium alloy in physiological solution.     

The effect of biological environment on the surface of titanium and plasma-sprayed layer of hydroxylapatite

The solubility of titanium samples with different surface coatings, i.e., hydroxylapatite (HA) powders, a two-layer coating of ZrO₅+HA on a titanium substrate in solution and of tooth implants after long-term functioning in the human organism, was studied. A minimum difference in solubility of titanium samples with different surface finishes (polished or grit blasted) was established. For the HA powders and coatings, the lowest solubility was observed with a coarse-grained HA–B powder and a coating made of that powder. Clinical tests of tooth implants after long implantation times were performed. A titanium implant (implantation 12 y), a titanium implant with a two-layer coating of ZrO₅+HA–A (implantation time 4 y) and a titanium implant with a two-layer coating of Al₅O₃+3% TiO₂)+ HA–A (implantation time 6 y) were studied. The results show that the titanium surface and HA–A layers were dissolved. Nevertheless, after 6 y implantation, total removal of HA–A coating from that part of implant set into the bone, was not observed.     

Electrophoretic deposition of HA/MWNTs composite coating for biomaterial applications

A composite coating of hydroxyapatite (HA)/multi-walled carbon nanotubes (MWNTs) has been fabricated by electrophoretic deposition (EPD). The nano powders of HA and MWNTs were dispersed in ethanol with total concentration of 0.005 g/mL and MWNTs 20% and 30% contents (wt). And the pH value of suspension was adjusted in a range from 4 to 5. After stabilization the mixture was ultrasonically treated for 3 h to form a stable suspension. Prior to the electrophoretic deposition, the titanium substrate was hydrothermally treated at 140 in NaOH (10 mol/L) solution for 6 h. A titanium sheet and circinal net of stainless steel were used as a cathode and an anode respectively, and a constant deposition voltage of 30 V was applied for 50-60 s in the EPD process. The thickness of the coatings was controlled from 10 mum to 20 mum. The samples of composite coating were then sintered in a resistance tube furnace in flowing argon at 700 for 2 h. The structure of the as prepared coating was characterized by SEM and XRD, and the bonding force of the coating/substrate was measured by an interfacial shear strength test. It is shown that the bonding strengths between the coating and the titanium substrate is as high as 35 MPa. The cell culture experiments indicate that the prepared composite coating of HA/MWNTs possesses good biocompatibility.