钛合金微弧氧化膜层耐磨性能的研究

本文通过对钛及钛合金在NaAlO2+H3PO4Na2SiO3溶液体系中,不同的微弧氧化电压、时间条件下,采用微弧氧化进行改性表面.通过分析实验现象和测试结果,研究工艺参数对所形成的膜层结构、形貌、厚度及耐磨性的影响.所得到的膜层摩擦系数鄱比基体的摩擦系数大;在试验中,发生了粘着磨损;表面粗造度对摩擦系数有一定的影响.从摩擦寿命来看,TA2膜层与TA10膜层在硅酸盐体系中的寿命较短.在NaAlO2+H3PO4体系中寿命较长.膜层厚度越厚,耐磨性越好.     

钛合金微弧氧化膜层耐磨性能的研究

本文通过对钛及钛合金在NaAlO2+H3PO4,Na2SiO3溶液体系中,不同的微弧氧化电压、时间条件下,采用微弧氧化进行改性表面。通过分析实验现象和测试结果,研究工艺参数对所形成的膜层结构、形貌、厚度及耐磨性的影响。所得到的膜层摩擦系数都比基体的摩擦系数大;在试验中,发生了粘着磨损;表面粗造度对摩擦系数有一定的影响。从摩擦寿命来看,TA2膜层与TA10膜层在硅酸盐体系中的寿命较短,在NaAlO2+H3PO4体系中寿命较长。膜层厚度越厚,耐磨性越好。     

阴/阳极电流密度对铝合金微弧氧化陶瓷膜耐蚀性的影响

为了弄清铝合金微弧氧化重要参数对其耐点蚀和微硬度的影响,在氢氧化钠和硅酸钠溶液中,保持阳极电流密度为15A/dm2,制备了阴/阳极电流密度比在0.6～0.8之间的铝合金微弧氧化陶瓷膜.结果表明:阴/阳极电流密度比对陶瓷膜的抗点腐蚀性和硬度有很强的影响;不同阴/阳极电流密度比所制备的陶瓷膜微观结构差异较大,陶瓷膜抗点腐蚀性和硬度的不同是由这种微观结构差异所引起的.     

钛合金微弧氧化膜微晶生长特性的研究

在Na₂CO₃-NaOH溶液中, 采用自制多功能单极性脉冲微弧氧化电源在TC4钛合金上制备了TiO₂薄膜. 利用XRD和SEM分别对氧化膜的相组成和表面形貌进行了分析. 结果表明, 在脉冲频率和电流密度分别固定为5000Hz和20A/dm²时, 氧化膜主要含锐钛矿和金红石相TiO₂,随着处理时间的延长, 金红石TiO₂的相对含量逐渐增加; 氧化膜呈多孔结构, 表面布满了尺寸在300nm～1μm之间的TiO₂颗粒, 随着处理时间的延长, 这些颗粒微孔的尺寸明显变大, 其密度逐渐减小.     

氧化时间对钛合金钻杆微弧氧化膜层结构和性能的影响

采用脉冲直流微弧氧化方法在钛合金钻杆表面制备了不同氧化时间下的TiO_2陶瓷膜层,用扫描电镜、X射线衍射仪、显微硬度计、球盘摩擦试验机及电化学工作站等分析了膜层的形貌、结构、组成以及膜层的硬度、摩擦磨损性能和耐蚀性。结果表明,随着氧化时间的延长,膜层的厚度增加,但膜层的硬度、耐磨性和耐腐蚀性先增加后降低。经不同氧化时间处理后,膜层的相结构主要由金红石型TiO_2和锐钛矿型TiO_2组成,此外还含有少量的Al2TiO5晶体和SiO_2非晶态。微观形貌分析表明,随着氧化时间延长,膜层表面粗糙度延长。在本实验条件下,当氧化时间为40min时,微弧氧化膜层的综合性能较好。     

大面积钛合金工件微弧氧化膜层性能研究

研究了影响大面积钛合金试样微弧氧化的因素,通过对溶液浓度以及添加剂含量的调整,优化了大面积微弧氧化的工艺,并对微弧氧化膜层进行了性能测试。结果表明,优化溶液制备的微弧氧化膜层性能优越,可用于大面积钛工件的微弧氧化膜层制备。     

氧化时间对TC11钛合金表面微弧氧化膜的耐烧蚀性能影响

在NaSiO_3(2g/L)、NaH_2PO_2(2g/L)、NaAlO_2(3g/L)、NaF(1g/L)的混合电解液中采用微弧氧化技术在TC11钛合金表面制备氧化时间不同的微弧氧化膜。利用扫描电子显微镜(SEM)、能谱仪(EDS)分析各氧化时间下膜层的表面形貌和各元素的含量,采用显微硬度计测出微弧氧化膜的硬度。以某型牵引火炮身管为实验平台,采用自行设计的烧蚀实验装置模拟发射状态下火炮身管内膛工况条件。在每次装药(14孔火药)为15g条件下,对膜层进行重复烧蚀检实验,检测微弧氧化膜的耐烧蚀性能。结果表明,氧化时间为20min时TC11表面微弧氧化膜具有良好的微观形貌,烧蚀20次后质量损失率最低,为0.0264%。本实验可以为火炮轻量化以及身管内膛耐烧蚀问题提供参考借鉴。     

钛合金表面微弧氧化膜层磨损性能研究

采用微弧氧化技术,以硅酸钠、磷酸钠溶液为电解液,在TC4钛合金表面制备出高硬度、高耐磨的微弧氧化膜层.用扫描电镜观测了膜层的显微结构,用X射线衍射分析其相组成,并对膜层进行了耐磨损和摩擦学性能实验.结果表明,膜层由过渡层、致密层和疏松层3层组成.其相组成主相为Al2TiO5,其次为Al2SiO5,并含有少量无定型SiO2.膜层的维氏硬度为8 470 MPa,是基体硬度的2倍多.采用45#钢作对磨副,载荷为5 kg,磨损时间20 min条件下,膜层的失重为0.25 mg,仅为基体的8%左右.     

钛合金低能耗微弧氧化研究

通过调整溶液电导率,研究了钛合金微弧氧化膜层单位面积上功率和能量消耗问题,并对氧化膜的粗糙度、相组成、微观形貌和绝缘性等性能进行了考核。结果表明,提高溶液电导率,能明显降低起弧电压,并且有效降低单位面积上功率及能量}肖耗。     

钛合金微弧氧化膜层摩擦学性能的研究进展

钛合金比强度优异,是适用于轻量化设计的轻金属合金,然而钛合金表面硬度低、耐磨性差的问题严重地限制了其实际应用。微弧氧化技术是提升钛合金摩擦学性能的有效方法。归纳了电解液体系的选用对钛合金微弧氧化膜层摩擦学性能的影响,梳理总结了工艺参数对微弧氧化膜层摩擦学性能的影响规律,详细介绍了微弧氧化复合技术改善钛合金微弧氧化膜层摩擦学性能的研究现状,进一步展望了改善钛合金微弧氧化膜层摩擦学性能的研究趋势和攻克难点。     

The effects of cathodic and anodic voltages on the characteristics of porous nanocrystalline titania coatings fabricated by microarc oxidation

Porous nanocrystalline titania films were prepared by microarc oxidation (MAO) of a titanium alloy keeping anodic voltage at 230–410 V and cathodic voltage at 20–45 V in a Na₂CO₃ and Na₂SiO₃ electrolytic solutions using an asymmetric pulse alternating current power supply. XRD, EDS and SEM were employed to characterize the phase, composition and microstructure of the films. It is found that the films consist of dominant rutile and little anatase phases. The phase, pore size and thickness of the coatings strongly depend on the applied voltage, consistent with the previous reports, and the cathodic voltage has an intense effect on the films' pitting corrosion performance in sodium chloride solution. The films prepared by keeping the anodic and cathodic voltages at 320 and 45 V, respectively, for 30 min were porous, with 200 nm to 4 μm pores and the pore walls composed of 100–300 nm rutile crystallites.     

恒定电压下微弧氧化陶瓷膜电学性质的研究

利用自制的数据采集系统研究了恒定电压下铝合金交流微弧氧化陶瓷膜形成过程中电学性质的变化规律.实验结果表明,微弧氧化过程中阴、阳极的峰值电流明显分为5个不同阶段;陶瓷膜形成过程中的动态正向电阻和电阻率随处理时间分阶段变化,而动态的反向电阻和电阻率变化不大.在微弧氧化过程中,各时刻的动态正、反向电阻值不同,一般情况下,动态正向电阻远大于反向电阻.     

Fatigue characteristics of VT22 titanium alloy with wear-resistant coatings

We study the influence of wear-resistant gas-thermal plasma and ion-plasma nitride coatings, diffusive electrochemical treatment, and vacuum nitriding on the fatigue resistance of specimens made of VT22 titanium alloy. The experimental results demonstrate that the wear-resistant hard coatings decrease the fatigue limit, whereas the procedure of sand-blasting increases the fatigue resistance of the alloy. Unlike diffusive coatings, plasma coatings suffer cracking and exfoliate from the surface of titanium alloy, which reveals their insufficient adhesion and high stiffness. The obtained results are quite urgent for the aircraft industry, where the VT22 alloy is extensively used. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 6, pp. 119–122, November–December, 2006.     

Sol-gel derived hydroxyapatite coatings on titanium substrate

Biomaterials, in particular those used for orthopaedic prostheses, consist of a metallic substrate, exhibiting excellent mechanical properties, coated with a ceramic layer, which guarantees resistance to the corrosion and an elevated bioactivity. In this paper the preparation of sol-gel films of hydroxyapatite, HA (Ca₁₀(PO₄)₆(OH)₂), on titanium substrate is described. The samples were obtained through the dip-coating method, starting from a colloidal suspension of hydroxyapatite. In order to increase the adhesion between the HA film and the metallic substrate, the same substrate has been preliminarily coated either with titanium oxide, TiO₂ (in the anatase or rutile phase), or calcium titanate, CaTiO₃ (perovskite). Also these latter films have been deposited from a sol-gel solution. The characterization of the films through XRD, SEM, and AFM gave good results for the crystallinity of the deposited HA; for what concerns the sample morphology, the films turned out to be homogeneous and crack-free.     

Electrocatalytic activity and anodic stability of electrodeposited ruthenium-rhodium coatings on titanium

The stabilizing effect of rhodium addition to ruthenium coatings on titanium under anodic polarization in acidic solutions is described. The addition of rhodium to the coating leads to both an overall improved stability of the electrode, and an increase of the electrochemically active surface area. The service-life of a Rh-Ru coating polarized at 0.12 A cm–2 in 0.5 mol dm–3 sulphuric acid is improved by at least two orders of magnitude, while deterioration of the electroactive surface area never exceeds 30%. The rotating ring-disc electrode measurements show the dissolution of the coating at potentials above the onset of the oxygen evolution reaction at 1.1 V versus SCE.     

The nanoporous structure of anodic aluminum oxide fabricated on the Au/Nb/Si substrate

We have studied the anodization behavior of an Al film evaporated on the Au/Nb/Si substrate and demonstrated an effective approach to fabricate the through-hole anodic aluminum oxide (AAO) template on the conducting substrate. The smoothness of the initial metal films and an appropriate wet etching of the oxide film anodized in the first step were found to be critical factors for successfully anodizing the Al film on Au surface. The barrier layer of the obtained AAO structure presented a convex and thinner characteristic, and the underlying Au surface became porous after the anodization. This phenomenon was similar to the case of anodizing the Al film on an ITO glass substrate and could be explained reasonably by the effect of high pressure O₂ gas impelling and H⁺ etching at the interface of the barrier oxide and the Au layer.     

Effects of high temperature treatment on microstructure and mechanical properties of laser-clad NiCrBSi/WC coatings on titanium alloy substrate

Laser-clad composite coatings on the Ti6Al4V substrate were heat-treated at 700, 800, and 900 °C for 1 h. The effects of post-heat treatment on the microstructure, microhardness, and fracture toughness of the coatings were investigated by scanning electron microscopy, X-ray diffractometry, energy dispersive spectroscopy, and optical microscopy. The wear resistance of the coatings was evaluated under dry reciprocating sliding friction at room temperature. The coatings mainly comprised some coarse gray blocky (W,Ti)C particles accompanied by the fine white WC particles, a large number of black TiC cellular/dendrites, and the matrix composed of NiTi and Ni₃Ti; some unknown rich Ni- and Ti-rich particles with sizes ranging from 10 nm to 50 nm were precipitated and uniformly distributed in the Ni₃Ti phase to form a thin granular layer after heat treatment at 700 °C. The granular layer spread from the edge toward the center of the Ni₃Ti phase with increasing temperature. A large number of fine equiaxed Cr₂₃C₆ particles with 0.2–0.5 μm sizes were observed around the edges of the NiTi supersaturated solid solution when the temperature was further increased to 900 °C. The microhardness and fracture toughness of the coatings were improved with increased temperature due to the dispersion-strengthening effect of the precipitates. Dominant wear mechanisms for all the coatings included abrasive and delamination wear. The post-heat treatment not only reduced wear volume and friction coefficient, but also decreased cracking susceptibility during sliding friction. Comparatively speaking, the heat-treated coating at 900 °C presented the most excellent wear resistance.     

Al和Li对镁基体氧化膜成分及厚度影响

合金元素对氧化膜性能影响很大。分别恒流氧化了纯镁、AZ91HP和Mg-Li合金并测量了氧化膜成分及厚度。EDX分析表明，在Mg—Li合金上形成的氧化膜P含量最高（39．39％），AZ91HP上最低（35．88％）；膜厚测量结果为Al和Li分别使氧化膜厚度稍微减少和大大增加。Al和Li元素对氧化膜性能影响可以用Mg^2＋、Al^3＋和Li^＋移动速度不同以及MgO、Al2O3和Li2O的PBR（Pilling—Bedweorth ratio）值不同来解释。