Frictional ignition of Ti40 fireproof titanium alloys for aero-engine in oxygen-containing media

The effect of friction pressure p and oxygen concentration xo on the fireproof performance of Ti40 titanium alloy was studied by frictional ignition test, the U--Xo relationship quantitatively describing the fireproof performance of Ti40 was established and the fireproof mechanism of Ti40 was analyzed by SEM, XRD and EDS. The results show that the p--xo relationship of Ti40 obeys parabolic rule. The varying range of xo is about 25% while p varies within 0.1-0.25 MPa. When Xo is 〉70%, Ti40 is ignited immediately at room temperature and develops into continual and steady burning, and the duration of burning is more than 10 s. The fireproof performance of Ti40 is better than TC4 while xo of Ti40 is at least 40% higher than TC4. When Xo is low, the fireproof performance of Ti40 is more sensitive to p; when Xo increases, it is more sensitive to Xo. The forming of fused oxides of V205, TiO2 and Cr203 with strong inner interaction during friction is the basic reason of high fireproof performance of Ti40.

Oxidation,Mechanical and Tribological Behaviors of the Ni/cBN Abrasive Coating-Coated Titanium Alloys

In order to improve the oxidation and wear resistance of blades tip of titanium alloys as well as the sealing performance of the gas turbine engine,a Ni/cBN abrasive coating was prepared on titanium alloys through composite electroplating.Oxidation,mechanical and tribological properties of the abrasive coating were investigated.Furthermore,the effect of the oxidation on the mechanical and tribological properties was also evaluated.Oxidation results revealed that the abrasive coating underwent slight oxidation within 700℃.Meanwhile,some intermetallic compounds,Ni3Ti,NiTi and NiTi2,were formed at the coating/substrate interface during oxidation.Due to the pinning effect of cBN particles and the different thermal expansion coefficients of the coating and substrate,the coating/substrate interface was cracked after oxidation at 700℃.Tensile results showed that the presence of coating reduced the strength of the alloy significantly at room temperature,while only marginal variations of the strength of the coated and uncoated specimens at elevated temperatures.Besides,the wear tests indicated that the coating had the excellent cutting ability and wear resistance,which can effectively protect the blades tip of titanium alloys.As the temperature increased,the wear resistance decreased due to the decrease in the mechanical properties of the Ni/cBN coating.

Fretting wear of micro-arc oxidation coating prepared on Ti6Al4V alloy

Micro-arc oxidation(MAO)coating was prepared on Ti6Al4V alloy surface and its characterizations were detected by Vickers hardness tester,profilometer,scanning electric microscope(SEM),energy dispersive X-ray spectrometer(EDX)and X-ray diffractometer(XRD).Fretting wear behaviors of the coating and its substrate were comparatively tested without lubrication under varied displacement amplitudes(D)in a range of 3-40μm,constant normal load(Fn)of 300 N and frequency of 5 Hz.The results showed that the MAO coating,presenting rough and porous surface and high hardness,mainly consisted of rutile and anatase TiO2 phases.Compared with the substrate,the MAO coating could shift the mixed fretting regime(MFR)and slip regime(SR)to a direction of smaller displacement amplitude.In the partial slip regime(PSR),lower friction coefficients and slight damage appeared due to the coordination of elastic deformation of contact zones.In the MFR,the friction coefficient of the coating was lower than that of the substrate as a result of the prevention of plastic deformation by the hard ceramic surface.With the increase of the displacement amplitude,the degradation of the MAO coating and the substrate increased extremely.The fretting wear mechanisms of the coating were abrasive wear and delamination with some material transfer of specimen.In addition,the coating presented a better property for alleviating fretting wear.

Dry sliding wear behavior and mechanism of AM60B alloy at 25-200 ℃

Dry wear tests under atmospheric conditions at 25-200 °C and loads of 12.5-300 N were performed for AM60B alloy. The wear rate increases with increasing the load; the mild-to-severe wear transitions occur under the loads of 275 N at 25 °C, 150 N at 100 °C and 75 N at 200 °C, respectively. However, as the load is less than 50 N, the wear rate at 200 °C is lower than that at 25 °C or 100 °C. In mild wear regimes, the wear mechanisms can be classified into abrasive wear, oxidation wear and delamination wear. Delamination wear prevailed as the mild-to-severe wear transition starts to occur; the delamination occurs from the inside of matrix. Subsequently, plastic-extrusion wear as severe wear prevails accompanied with the transition. The thick and hard tribo-layer postpones the mild-to-severe wear transition due to restricting the occurrence of massive plastic deformation of worn surfaces.

Corrosion and wear resistance of coatings produced on AZ31 Mg alloy by plasma electrolytic oxidation in silicate-based K2TiF6 containing solution:Effect of waveform

In this research,plasma electrolytic oxidation coatings were prepared on AZ31 Mg alloy in a silicate-based solution containing K_(2)TiF_(6) using bipolar and soft sparking waveforms with 10,20,and 30%cathodic duty cycles.The coatings displayed a net-like surface morphology consisted of irregular micro-pores,micro-cracks,fused oxide particles,and a sintered structure.Due to the incorporation of TiO_(2) colloidal particles and the cathodic pulse repair effect,most of the micro-pores were sealed.Long-term corrosion performance of the coatings was investigated using electrochemical impedance spectroscopy during immersion in 3.5 wt.%NaCl solution up to 14 days.The coating grown by the soft sparking waveform with a 20%cathodic duty cycle having the lowest porosity(6.2%)and a sharp layer concentrated in F element at the substrate/coating interface shows the highest corrosion resistance.The friction coefficient of this coating has remained stable during the sliding even under 5 N normal load,showing relatively higher wear resistance than other coatings.The coating produced using the equivalent unipolar waveform,as the reference specimen,showed the highest friction coefficient and the lowest wear resistance despite its highest micro-hardness.

Dry sliding wear behavior of Ti-6Al-4V alloy in air

The dry sliding wear properties of Ti-6Al-4V alloy sliding against GCr15 steel under different velocities(between 0.2 and 1.2 m/s)and applied loads(from 30 to 90 N)were tested using a pin on disk tester in air. The wear occurred on both surfaces of the tested couplings. The wear rate of the Ti-6Al-4V alloy ranged from 23.0 to 123.8 mg/km. The wear of Ti-6Al-4V samples was in severe wear. The wear rate of Ti-6Al-4V samples increased with the increasing of load and shows a minimum on the curves of wear rate versus sliding velocity. SEM morphologies of worn surfaces and debris were observed. Phases in the debris were analyzed by means of XRD spectra.

TC4表面掺La微弧氧化涂层的显微结构与耐磨性的研究

针对TC4钛合金在服役期间耐磨性较差等问题,本文在乙酸钙-六偏磷酸钠电解液体系下运用微弧氧化工艺在TC4钛合金表面制备出掺La陶瓷涂层。重点研究了电解液中掺杂La(NO_(3))_(3)对TC4钛合金微弧氧化涂层(MAO)耐磨性的影响。利用XRD、SEM、显微硬度计、摩擦磨损试验机、涂层附着力划痕仪等仪器对不同La(NO_(3))_(3)掺杂量下的微弧氧化涂层的物相组成、微观形貌、厚度、显微硬度、摩擦因数、结合力等指标进行表征。结果表明:随着La(NO_(3))_(3)掺杂量增加,MAO涂层由HAp、A-TiO_(2)、R-TiO_(2)、La_(2)O_(3)相组成。掺La陶瓷涂层厚度虽略有减小,但致密性有所提高。涂层的显微硬度先增大后减小、摩擦因数先减小后增大。当La(NO_(3))_(3)掺杂量为6 g/L时,涂层显微硬度提高31.18%,涂层与基体结合力提高30.59%,MAO涂层摩擦因数最小,约为0.55。

钛合金摩擦磨损性能及减磨方法研究进展

钛合金具有比强度高、抗腐蚀性强、耐高温以及生物相容性好等优点,在汽车制造、生物医疗等众多领域具有重要应用。但钛合金的摩擦磨损性能较差,会影响机械系统的使用寿命和可靠性。首先论述了摩擦磨损过程中摩擦层的形成过程以及摩擦层对钛合金磨损机理的作用,分析了润滑条件、环境温度、滑动速度、载荷等工况条件对钛合金摩擦磨损性能的影响规律。其次,对比总结了钛合金减磨的常见工艺方法及优缺点,指出了当前钛合金磨损机理研究和性能改善方面存在的问题。最后,对今后的研究工作进行了展望:将实验与仿真相结合,阐明钛合金摩擦层和磨损机理的动态变化规律;考虑各种环境因素对钛合金磨损机理的影响,完善钛合金磨损机制图;通过对多种技术协同配合时的工艺参数进行优化,促进钛合金表面强化复合技术的发展,从而提升钛合金的耐磨减摩性能。

DOUBLE GLOW PLASMA SURFACE ALLOYING OF Ti6A14V AND TiAl

In order to improve the wear resistance of titanium alloy Ti6Al4V and high temperature oxidation resistance of intermetallic compound TiAl, the Double Glow Plasma Surface Alloying Technique (DG technique) was applied to modify the surface properties of these materials. Mo, Nb, Cr, Ni were diffused into the substrate materials to form alloyed layers with different properties. This paper shows the microstructure, microhardnesses, distributions of the alloy elements on the alloyed layers. Wear and high temperature oxidation tests were carried out. Test results indicate that the wear resistance of Ti6Al4V and the high temperature oxidation resistance of TiAl were improved significantly.

镀钛对2195铝锂合金耐磨和腐蚀性能的影响

通过摩擦磨损试验和电化学工作站等测试,研究了2195-T6铝锂合金表面镀钛处理前后的摩擦磨损性能和电化学性能,探讨了浸泡实验的腐蚀机制。结果表明:镀钛后铝锂合金表层的纳米压痕硬度略有提高,表层晶粒得到了细化;镀钛前后的摩擦系数基本相同,磨损性能得到了提高;镀钛后铝锂合金的腐蚀电位提高,腐蚀电流密度减小,阻抗谱半径变大。3.5%NaCl溶液中的浸泡实验显示,镀钛试样的点腐蚀明显改善,这是由于合金表面形成的钛膜起到了隔离保护作用。

La(NO_(3))_(3)掺杂对TC4微弧氧化/水热复合涂层显微结构和耐磨性的影响

作为生物医用材料,TC4钛合金在骨组织再修复领域中临床使用量很大,中国每年的消耗量约为百万件以上。但TC4钛合金耐磨性低、生物活性差等问题严重制约其工程应用领域的扩展。为此,采用微弧氧化/水热合成复合技术在TC4表面制备微弧氧化/水热复合涂层,研究水热合成液中La(NO_(3))_(3)掺杂量对TC4钛合金微弧氧化/水热涂层的相组成、微观形貌、显微硬度、耐磨性等参数的影响作用。利用XRD、SEM、显微硬度计、摩擦磨损试验机等手段对TC4钛合金微弧氧化/水热涂层进行表征。研究结果表明:TC4钛合金微弧氧化/水热涂层相组成主要由锐钛矿型TiO_(2)和羟基磷灰石组成。经过水热处理后合成液中La^(3+)进入到复合涂层中,参与涂层反应。随着La(NO_(3))3掺杂量增加,获得的复合涂层中羟基磷灰石相含量先增加后降低。当La(NO_(3))_(3)掺杂量超过24 mmol/L时,涂层表面变得更为光滑。TC4钛合金微弧氧化/水热涂层的显微硬度先降低后增加,且其摩擦系数先增大后减小。当La(NO_(3))_(3)掺杂量达到24 mmol/L时,涂层的显微硬度达到最小值,约为271.8 HV9.8 N;涂层摩擦系数达到最大值,约为0.8~0.9。

TC4钛合金二维超声振动车削性能研究

钛合金因其优越的物理和化学性能被广泛应用于航空航天、轮船船舶、武器制备等各类高精尖领域,但如何克服其高比热容、低热导率特性以实现高质高效加工也成为了机械加工领域的热点问题。二维超声振动车削加工工艺具有断续车削特性,能显著提升复合材料、脆性材料及陶瓷材料等难加工材料的车削效果。因此,采用二维超声振动车削工艺,对TC4钛合金进行车削加工,并从多种加工性能方面与传统车削进行对比。实验结果表明,二维超声振动车削工艺能够有效提高工件加工质量并降低切削过程中车削力,减小刀屑接触滑动区域与粘着区域的摩擦系数,延长刀具使用寿命的同时使其具有良好的断屑能力。另外,超声振动车削还会增大工件表面的加工硬化程度,细化表层晶粒,并增加工件表面残余应力。

TA15钛合金高温摩擦磨损性能研究

目的 为探究TA15钛合金高温耐磨性能的潜力,研究了TA15钛合金在室温~800℃下的摩擦磨损性能。方法 利用Rtec摩擦磨损试验机(Rtec,San Jose,USA)进行TA15钛合金的摩擦磨损性能测试,通过激光共聚焦显微镜、JSM-7800F扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)等手段,分析了TA15钛合金在不同温度下的磨痕形貌、成分变化以及磨损机理。结果 在不同试验温度下,微观组织没有出现明显变化,主要为等轴α相和β相;不同温度下的摩擦因数波动不大,从室温的0.279下降到600℃的0.224,而在800℃时,表面严重氧化导致摩擦因数增大到0.309;在室温~400℃时,试样表面磨痕不断变窄变浅,犁沟和磨屑不断减少,而到400℃以上时磨痕逐渐变宽,比磨损率也大幅增大,且在600℃时的磨损量最大;在600℃时,以氧化磨损为主,并伴随着磨粒磨损和黏着磨损,且表面磨痕形貌和宽度比较均匀;在800℃时磨损表面以黏着磨损和氧化磨损为主,并伴随着高温焊接的发生。结论 TA15合金表面的O元素含量随温度的升高而逐渐升高,并且氧化反应主要发生在β相内。随着试验温度的升高,TA15钛合金磨损表面的氧化磨损现象也更加明显。

不同方法制备的微弧氧化涂层摩擦磨损特性的研究现状

镁、铝、钛及其合金具有比强度高、资源丰富、加工性能好等优点,在机械、航空航天、生物医药等领域得到广泛应用,但由于镁、铝、钛及其合金的耐磨性较差,严重限制了其在各个领域的应用。从微弧氧化复合涂层的形成原理和制备方法出发,系统综述了在镁合金、铝合金、钛合金等轻质合金材料表面采用各种微弧氧化复合技术制备的涂层的摩擦磨损性能方面的研究现状,指出目前微弧氧化技术存在的问题与未来发展方向,为后续研究提供一定参考。

TC4钛合金表面激光冲击强化-微弧氧化涂层的组织和性能

通过激光冲击强化(LSP)在TC4钛合金表面制备细晶粒过渡层,再采用微弧氧化(MAO)制备LSP-MAO复合涂层,研究TC4钛合金表面MAO涂层及LSP-MAO复合涂层的显微组织、相结构、显微硬度和耐磨性。结果表明:激光冲击强化处理后,TC4钛合金衍射峰变宽,表层晶粒明显细化。与MAO涂层相比,LSP-MAO复合涂层表面的孔径更小,表面更加平整,显微硬度和强化层深度有所增加,其中激光冲击2次时显微硬度最高,达到636.3 HV0.025(距离表面30μm处),其强化层最大深度达到390μm。LSP-MAO涂层的耐磨性均优于MAO涂层,其中激光冲击强化2次时LSP-MAO复合涂层耐磨性最好。

钛合金表面激光熔覆高熵合金涂层研究进展

钛合金具有比强度高、热膨胀系数低、良好生物相容性的优点,在航空航天、医疗器械以及船舶运输等领域受到广泛的应用。然而,钛合金存在耐磨性差、抗高温氧化性差以及耐腐蚀性差等问题需要解决。作为新兴材料,高性能的高熵合金(HEA)近年来发展空间巨大。研究者发现采用激光熔覆技术在钛合金表面涂覆HEA可显著提升耐磨性、抗高温氧化性以及耐腐蚀性。对钛合金表面激光熔覆HEA涂层研究领域的最新进展进行了综述,首先介绍钛合金表面激光熔覆HEA涂层的成分设计,接下来分析了工艺参数对钛合金表面激光熔覆HEA涂层质量的影响,再者较为系统地探讨了钛合金表面激光熔覆HEA涂层对钛合金耐磨性、抗高温氧化性以及耐腐蚀性的影响,最后对钛合金表面激光熔覆HEA涂层的发展方向进行了展望。

冷风静电微量润滑换热特性及其钛合金铣削加工性能研究

针对钛合金铣削温度高、刀具寿命短的问题,提出并开展了基于冷风静电微量润滑(CAEMQL)技术的钛合金加工新方法研究。在构建冷风静电微量润滑系统的基础上,研究了冷风荷电气雾的换热特性和钛合金铣削性能,通过刀具磨损揭示了刀具延寿机理。结果表明,与微量润滑、静电微量润滑和冷风微量润滑相比,冷风静电微量润滑具有更高的临界热流密度和更好的稳态换热性能;与微量润滑相比,冷风静电微量润滑下的切向铣削力Fx下降了21%,法向铣削力Fz下降了17%,铣削温度下降33%,工件表面粗糙度Ra值减少26%;冷风静电微量润滑下切屑自由面的褶皱高度降低,切屑背面划痕减少;低温压缩空气和荷电切削液协同作用抑制了刀具的粘着磨损,刀具寿命提高41%。

电解质对钛合金微弧氧化放电方式和耐磨性能的影响

目的通过比较添加微量磷酸盐对放电方式的影响,表征各膜层的微观结构与成分组成,研究分析放电方式差异对膜层耐磨性能的影响。方法在3组电解液中分别进行TC4钛合金微弧氧化,以磨损率为指标判定每组的最优配比。通过扫描电子显微镜(SEM)观察膜层表面与截面微观形貌。使用X射线能量色散谱仪(EDS)分析膜层表面和磨损区域的元素分布情况。使用X射线衍射仪(XRD)表征膜层物相结构组成,通过维氏显微硬度计测量膜层的硬度,使用摩擦磨损试验机进行膜层摩擦学性能测试,并通过三维形貌仪分析磨痕轮廓。结果在铝酸盐电解液中添加磷酸盐电解质后会增强A、C型放电,减弱B型放电,使制得膜层的缺陷(微孔与微裂纹)明显增多,产生了较厚的疏松层,并且随着电解液中磷酸根离子的增多,放电方式进一步受影响,膜层磨损率也大幅增加。而不添加磷酸盐的20 g/L铝酸盐浓度制备的钛合金微弧氧化膜层在15 N高载荷滑动干摩擦下的摩擦系数为0.6~0.7,磨痕窄且浅,磨损率仅为基体的7.22%。结论磷酸盐电解质极易引起杂质放电,导致微弧氧化反应时B型放电显著减弱,A、C型放电大幅增加,导致膜层致密性显著降低,严重降低了微弧氧化膜层的耐磨性能。20 g/L铝酸盐电解液制备的钛合金微弧氧化膜层缺陷少、硬度高、厚度大,显著改善了高载荷下钛合金的耐磨性能。

钛合金表面CrN涂层高温氧化及力学性能

采用热丝增强等离子体磁控溅射技术,在Ti6Al4V(TC4)基体表面沉积单相CrN涂层,并分别在温度为400、500、600、700、800℃下空气中退火。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)与能谱(EDS)、Raman光谱、原子力显微镜(AFM)、X射线荧光光谱仪(XRF)、划痕仪、纳米压痕仪、台阶仪和摩擦磨损仪分析涂层的物相组成、微观形貌、成分及力学性能。随着退火温度的升高,CrN所有取向的峰位均向右移动接近标准峰位,内应力得到释放。当退火温度达到600℃后,涂层表面氧化迹象明显,粗糙度升高,出现白色颗粒状Cr_(2)O_(3)。随退火温度升高,涂层与基体结合力提高,在800℃时临界失效载荷达到25.2 N;涂层硬度和弹性模量下降,硬度从未退火的24.86 GPa降至800℃的15.23 GPa,弹性模量从327 GPa降至260 GPa;涂层耐磨性小幅下降,磨损量从未退火的0.78×10^(-16)m^(3)/(m·N)上升至11.74×10^(-16)m^(3)/(m·N),但均远低于TC4基体的磨损量10371.61×10^(-16)m^(3)/(m·N)。划痕与摩擦磨损检测结果中,涂层均未出现分层及剥落现象。采用热丝增强等离子体磁控溅射技术在钛合金表面制备的CrN涂层,在高温环境下保持较高的耐磨损性能和与基体良好的结合力,提高了软质不耐磨的TC4基体在高温磨损环境的使用寿命。