钛等离子渗氧研究

探讨了空心阴极效应 (HollowCathodeEffect)、离子轰击对钛氧化层结构的影响。结果表明 ,离子轰击加强氧的离化、促进渗氧 。

纯钛等离子涂层圆柱状骨内种植体与周围骨界面的三维结构分析

目的:通过组织形态学的方法评价和分析纯钛等离子涂层圆柱状骨内种植体与周围骨界面的三维结构情况。方法:选择2只成年雄性比格犬,拔除双侧下颌第二、第四前磨牙,自行愈合3个月,植入纯钛等离子涂层圆柱状种植体,共8枚。3个月后处死动物,取下包含种植体的下颌骨,固定后用自动磨片机切片、染色、拍照数字化后输入计算机构建三维结构模型并分析。结果:种植体平均骨接触率(bone contact ratio,BCR)为(64.5±5.3)%,最高在舌侧和上部,最低在近远中和底部。平均骨体积率(bone volume ratio,BVR)为(68.9±4.4)%,最佳在舌侧150~225μm带和上部,最差在近远中0~75μm带和底部。结论:纯钛等离子涂层圆柱状骨内种植体与周围骨界面的三维结构能清晰的构建出来,二者能形成良好的结合,特别是在皮质骨致密的舌侧和上部。

辉光等离子渗氮对纯钛铸件表面性能的影响

使用NH3在氮化炉中对纯钛铸件进行辉光等离子渗氮。分别应用X线衍射仪XRD、显微硬度计、扫描电镜、摩擦磨损实验及电化学实验研究等离子渗氮对纯钛铸件机械性能、摩擦学性能、耐腐蚀性的影响。铸造纯钛表面氮化处理后,颜色呈暗金黄色,表面由TiN、Ti2N相及氮在钛中的固溶体α-Ti(N)组成,显微硬度、耐磨性显著提高,在人工唾液中的耐腐蚀性亦明显提高。

ST12钢高能喷丸后表面等离子渗钛

采用高能喷丸方法,在ST12钢表面获得一定厚度的纳米晶层。喷丸处理后的样品在温度500℃,保温时间为3 h下进行等离子渗钛处理,可以获得一定厚度的渗钛层。运用光学显微镜,扫描电镜,X射线衍射分析和电化学测试系统等测试技术对纳米晶层、渗钛层的组织结构、显微硬度与耐腐蚀性等进行了研究。结果表明,采用高能喷丸法,在ST12钢表面获得一定厚度的纳米晶层。高能喷丸处理可以显著地降低等离子渗钛的温度。渗钛处理后的ST12钢,其显微硬度和耐腐蚀性能得到了提高。

42CrMo钢的钛催渗等离子渗氮工艺

研究了不同渗氮时间下钛元素对42CrMo钢常规离子渗氮工艺的作用效果,表征分析了不同渗氮工艺下试样表面的渗层组织及性能。结果表明,钛催渗离子渗氮试样的表面硬度和渗层深度均明显高于常规离子渗氮。在535℃×3 h的工艺条件下,钛催渗离子渗氮试样渗层的表面硬度达到887.4 HV0.2,渗氮层厚度约为400μm。钛元素的加入促进了氮元素的渗透和扩散,在试样表面生成高硬度化合物TiN。相较于相同保温时间下的常规离子渗氮,钛催渗离子渗氮试样表面硬度提高了60 HV0.2,渗层厚度增加了80μm,渗氮效率提升了约25%。与常规离子渗氮相比,钛催渗离子渗氮工艺具有显著优势,不仅有利于改善渗层组织性能,增强渗氮效果,还提高了渗氮效率,使渗氮周期明显缩短。

钛铁合金中Al、Cu、Mn、Si、P检测方法的探讨与应用

钛铁合金是钢厂普遍使用一种铁合金原料,其主要成分钛均做进厂质量控制,其他硅、铝、锰、铜及磷等微量元素一般都不做质量控制。随着高端客户对钢的窄成分控制要求越来越高,生产中对合金中除主元素以外的微量元素的检测控制要求也随之体现出来。检测室只能采取传统的化学检测方法依次进行检测,其过程耗时长,至少需要两天才能完成。为了满足日益增长的检测需求需要,降低员工劳动强度,提高工作效率,化验室开展了采用电感耦合等离子体发射光谱仪检测钛铁中Al、Cu、Mn、Si、P元素含量的方法实验,代替了传统的国标方法,数据稳定可靠,效果较好。

粉末冶金信号轮的模具设计与优化

分析了粉末冶金信号轮的特殊结构、模冲的组合形式及圆度控制对加工的影响;从如何构造模具的局部形状、模具的选材、模具的间隙、模具的表面涂层等方面,对粉末冶金信号轮成形压制模具进行优化设计,满足图纸要求,提高模具的耐用度。同时,生产出来的信号轮具有高密度、高精度、高质量特性。

宽光谱在线弯晶谱仪研制

研制了高精度在线准直、超宽光谱范围和高能谱分辨的在线凸圆柱面弯晶谱仪。使用耦合针状CsI(Tl)闪烁体的大面阵CMOS相机对X射线光谱进行在线测量,用QTZ(1010)(2d=0.851 2 nm)X射线晶体的能谱测量范围是1.84~7.38 keV,能谱分辨880@2.375 keV,动态范围≥1 000。在神光-Ⅲ主机高功率激光装置上,对钛激光等离子体发射的X射线谱进行实验测量,获得了优质的光谱图像;对钛离子X射线精细结构光谱进行了辨识,与理论计算和其他实验结果吻合。该谱仪用于神光-Ⅲ主机通用诊断搭载平台,具有抗瞬发超强电磁脉冲干扰能力,工作稳定。

Effects of graphite content on microstructure and tribological properties of graphite/TiC/Ni-base alloy composite coatings

In order to reduce the friction coefficients and further improve the anti-wear properties of Ni-base alloy coatings reinforced by TiC particles,graphite/TiC/Ni-base alloy（GTN） coatings were prepared on the surface of 45 carbon steel.The effects of graphite content on the microstructure and tribological properties of the GTN coatings were investigated.The results show that the addition of graphite to the GTN coatings may greatly reduce the friction coefficients and improve their wear resistance.The 6.56GTN and 12.71GTN coatings exhibit excellent integrated properties of anti-friction and wear resistance under low and high loads,respectively.Under a low load,the wear mechanisms of the GTN coatings are mainly multi-plastic deformation with slight abrasive wear and gradually change into mixture of multi-plastic deformation,delamination and micro-cutting wear with the increase of graphite fraction.As the load increases,the main wear mechanisms gradually change from micro-cracks,micro-cutting and adhesive wear to micro-cutting and micro-fracture with the increase of graphite fraction.

纯Fe表面机械研磨处理对Ti原子扩散特性影响的第一性原理计算及实验验证

基于密度泛函理论的第一性原理方法,计算了空位对纯Fe晶格常数、局域态密度和热力学参数的影响规律,结合Ti原子在纯Fe中的过渡态搜索,阐明了空位对纯Fe表面Ti原子扩散特性的作用机制。模拟计算表明,引入空位后,体系晶格常数和局域态密度减小,Helmholtz自由能和结合能降低,声子振动内能、熵值和等容热容增加。bcc-Fe的3×3×3超胞含一个空位和两个空位时Ti原子的扩散势垒分别为0.659 eV和0.353 eV。不同温度下体系的扩散系数表明,纯Fe经表面机械研磨处理(SMAT)后,其在673 K即可达到未机械研磨时1 073 K的Ti原子扩散效果。在实验验证环节,借助扫描电镜(SEM)、能谱(EDS)仪和X射线衍射(XRD)仪观察及表征了Fe试样经SMAT处理和673 K双层辉光等离子渗Ti处理后的微观组织、截面元素分布及渗层物相结构。结果表明,增加空位浓度可以有效降低等离子渗钛温度,纯Fe表面生成了12μm左右的渗Ti层。本工作可为通过调控空位浓度实现低温渗钛的研究提供参考。

Microstructure characteristics and mechanical properties of TiB/Ti-1.5Fe-2.25Mo composites synthesized in situ using SPS process

TiB/Ti-1.5Fe-2.25Mo composites were synthesized in situ using the spark plasma sintering （SPS） method at temperatures of 850-1150 °C. The effect of the sintering temperature on microstructure and mechanical properties of the composites was investigated. The results indicate that the aspect ratio of the in situ synthesized TiB whiskers in Ti alloy matrix decreases rapidly with an increase in sintering temperature. However, both the relative density of the sintered specimens and the volume content of TiB whiskers in composites increase with increasing sintering temperature. Thus, the bending strength of the composites synthesized using SPS process increases slowly with increasing the sintering temperature from 850 to 1150 °C. TiB/Ti-1.5Fe-2.25Mo composite synthesized at 1150 °C using SPS method exhibits the highest bending strength of 1596 MPa due to the formation of fine TiB whiskers in Ti alloy matrix and the dense microstructure of the composite.

Bimodal-grained Ti fabricated by high-energy ball milling and spark plasma sintering

Bimodal-grained Ti containing coarse and fine grains was fabricated by high-energy ball milling and spark plasma sintering (SPS). The microstructure and mechanical properties of the compacts sintered by Ti powders ball-milled for different time were studied. Experimental results indicated that when the ball-milling time increased, the microstructure of sintered Ti was firstly changed from coarse-grained to bimodal-grained structure, subsequently transformed to a homogeneous fine-grained structure. Compared with coarse-grained Ti and fine-grained Ti, bimodal-grained Ti exhibited balanced strength and ductility. The sample sintered from Ti powders ball-milled for 10 h consisting of 65.3% (volume fraction) fine-grained region (average grain size 1 μm) and 34.7% coarse-grained region (grain size > 5 μm) exhibited a compress strength of 1028 MPa as well as a plastic strain to failure of 22%.

Hydrogen storage properties of Mg-TiO_2 composite powder prepared by arc plasma method

Mg-based Mg-TiO2 composite powder was prepared by arc plasma evaporation of the Mg＋5%TiO2 mixture followed by passivation in air. ICP, XRD and SEM techniques were used to characterize the composition, phase components and microstructure of the composite powder. The hydrogen sorption properties of the composite powder were investigated by DSC and PCT techniques. According to the data from PCT measurements, the hydrogenation enthalpy and entropy changes of the composite powder are calculated to be-71.5 kJ/mol and-130.1 J/（K·mol）, respectively. Besides, the hydrogenation activation energy is determined to be 77.2 kJ/ mol. The results indicate that TiO2 added into Mg by arc plasma method can act as a catalyst to improve the hydrogen sorption kinetic properties of Mg.

Wear modes in open porosity titanium matrix composites with TiC addition processed by spark plasma sintering

This work focused on the influence of TiC reinforcing particles on the tribological properties of titanium matrix composites(TMCs)with open porosity,processed by spark plasma sintering(SPS).Materials composed of an equimolar mixture of Ti and TiH2 with 0,3,10 and 30 vol.% of TiC were sintered at 850 ℃.Nanoindentation and wear tests were carried out to assess the nanohardness and the wear resistance in a tribometer with a reciprocating sliding ball-on-flat configuration.Results showed a nanohardness increment from 5 to 14 GPa with increasing TiC content.The coefficient of friction(CoF)showed a minimum of 0.2 for 10% TiC grade,which also showed the lowest wear rate.For the low TiC content sample,adhesive wear with severe plastic deformation was identified.Meanwhile,medium content TiC sample showed a mechanical mixed layer(MML),whereas high TiC content composite showed abrasive as the main wear mechanism.In conclusion,the wear mechanisms,CoFs and wear volume changed with TiC content.

Wear resistance of TC4 by deformation accelerated plasma nitriding at 400 °C

An integrated low temperature nitriding process for TC4（Ti6Al4V） has been developed and the effect on wear resistance has been investigated. Through the process of solid solution strengthening—cold deformation—nitriding at 400℃, the TC4 alloy is nitrided on surface and dispersion strengthened in bulk at the same time. The white nitriding layer is formed after some time of nitriding. The nitriding speed increases with the deformation degree. The construction was investigated by XRD and the nitride is Ti3N（2-X）. The wear test was carried out and results exhibit that the nitrided samples have better wear resistance.

Mechanical and corrosion properties of Ti-35Nb-7Zr-xHA composites fabricated by spark plasma sintering

To improve the bioactivity of Ti?Nb?Zr alloy,Ti?35Nb?7Zr?xHA(hydroxyapatite,x=5,10,15and20,mass fraction,%)composites were fabricated by spark plasma sintering.The effects of the HA content on microstructure,mechanical and corrosionproperties of the composites were investigated utilizing X-ray diffraction(XRD),scanning electron microscope(SEM),mechanicaltests and electrochemical tests.Results show that all sintered composites are mainly composed ofβ-Ti matrix,α-Ti andmetal?ceramic phases(CaO,CaTiO3,CaZrO3,TixPy,etc).Besides,some residual hydroxyapatites emerge in the composites(15%and20%HA).The compressive strengths of the composites are over1400MPa and the elastic moduli of composites((5%?15%)HA)present appropriate values(46?52GPa)close to that of human bones.The composite with15%HA exhibits low corrosion currentdensity and passive current density in Hank's solution by electrochemical test,indicating good corrosion properties.Therefore,Ti?35Nb?7Zr?15HA composite might be an alternative material for orthopedic implant applications.

Porous ceramic coating formed on 316L by laser cladding combined plasma electrolytic oxidation for biomedical application

In order to improve the bioactivity of 316L stainless steel,a titanium layer was prepared on the surface of 316L by laser cladding(LC),followed by plasma electrolytic oxidation(PEO)to form a porous ceramic coating on titanium layer.The morphologies,microstructure and compositions of the coated samples were characterized by 3D surface profiler,SEM,EDS,XRD and XPS.The corrosion resistance and bioactivity of the coatings were evaluated by potentiodynamic polarization and immersion test in simulated body fluid(SBF),respectively.The results showed that the porous ceramic coating mainly consisted of anatase and rutile,and highly crystalline HA was also detected.The main elements of the PEO coating are Ca,P,Ti and O.The LC+PEO composite bio-coating has more excellent corrosion resistance than the 316L substrate in simulated body fluid.Furthermore,the composite coating could effectively improve the bioactivity of 316L stainless steel.

Microstructure and mechanical properties of three kinds of titanium alloys by SPS

High-density titanium alloys with different grains were prepared by spark plasma sintering(SPS) at 900 ℃ and 15 MPa using spherical powder generated by the plasma rotating electrode process(PREP) and nonspherical powders generated by hydrogenation-dehydrogenation(HDH) and molten salt electrolysis(MSE) as raw materials. Studies have shown that the PREP sample is a dense lamellar α structure and that the sample is clean. The microstructure of the HDH sample is composed of equiaxed α and lamellar α structures, and there are many flaws on the surface of the sample. The MSE samples are composed of α lamellar and coarse equiaxed crystals. The integral grain size is bulky, there are many irregular pores in the samples, and the samples are not clean. Of the three samples, the HDH sample has the largest compressive strength(526.85 MPa) and hardness(HV 293.1) but poor plasticity(compression strain is 26.61%);the compressive strengths of the PREP and MSE samples are 268.47 and 251.23 MPa, the compressive strains are 45.08% and 17.44%, and the microhardness values are HV138.6 and HV203.4, respectively.

Theoretical and experimental investigation of Ti alloy powder production using low-power plasma torches

This study was carried out to investigate the possibility of titanium alloy metal powder production using low-power plasma torches.An argon DC non-transferred arc plasma torch was designed,and numerical analysis was conducted to determine the plasma jet properties and wire temperature.The highest velocities inside the nozzle attachment were between 838 and 1178 m/s.The velocities of the jets at the apex were between 494 and 645 m/s for different gas flow rates.The studied plasma gas flow rates had no significant effect on the effective plasma jet length.It was shown that the plasma jet length can be estimated by numerical analysis using the temperature and velocity changes of the plasma jet over distance.It was observed that the powders produced were spherical without any satellites.As a result of this study,a plasma torch was developed and powder production was performed successfully by using relatively low torch power.

Microstructural evolution in a powder metallurgical Ti-7Mo alloy with continuous oxygen gradient

A titanium alloy containing continuous oxygen gradient was prepared by powder metallurgy(P/M) and the composition–property relationship was studied on a single sample. The alloy was sintered with layered powder of different oxygen contents via vacuum sintering and spark plasma sintering(SPS), respectively. After subsequent heat treatments, high-throughput characterizations of the microstructures and mechanical properties by localized measurements were conducted. The Ti-7% Mo(molar fraction) alloy with an oxygen content ranging from 1.3×10^(-3) to 6.2×10^(-5)(mass fraction) was obtained, and the effects of oxygen on the microstructural evolution and mechanical properties were studied. The results show that SPS is an effective way for fabricating fully dense Ti alloy with a compositional gradient. The average width of α′ phase coarsens with the increase of the content of oxygen. The content of α″ martensitic phase also increases with the content of oxygen. At oxygen contents of 3×10^(-3) and 4×10^(-3)(mass fraction), the Ti alloys present the lowest microhardness and the lowest elastic modulus, respectively. The results also indicate that the martensitic phases actually decrease the hardness of Ti-7Mo alloy, and oxygen effectively hardens the alloy by solid solution strengthening. Therefore, the high-throughput characterization on a microstructure with a gradient content of oxygen is an effective method for rapidly evaluating the composition–property relationship of titanium alloys.