大功率CO2激光原位直接反应合成TiN/Ti 复合材料的研究

使用大功率CO₂激光原位直接反应合成TiN /Ti 复合材料, 分析了材料的微观结构、物相组成、成分及显微硬度分布。结果发现: 氮化层是富钛结构的, 由TiN 相和α-Ti 构成, TiN 以枝晶形式在氮化层均匀分布。材料横截面显微硬度连续变化。氮化层的氮化程度随激光作用时间的增加而增加, 辐照的激光能量密度越高, 氮化层的厚度越大。激光功率密度, 激光扫描速度, 氮气喷射压强分别为3. 35×105W·cm-2, 300mm·min-1, 0.35M Pa 时, 材料表面硬度值达到Hv1600, 氮化层的厚度有350Lm。      

航空钛合金表面激光气体氮化研究

利用激光气体氮化方法,实现了钛合金表面氮化处理。结果表明,当功率密度大于6．5×10^5W．cm-2时,生成物以TiN为主。由于Al的饱和蒸气压和蒸发速率均高于Ti,因此,在熔池表面形成贫铝层,促进了表面层Ti的氮化。热力学分析表明,激光熔池内生成TiN的反应较生成AIN的反应更具有热力学优势。     

几种难熔过渡金属的激光氮化

多脉冲激光辐射使置于氮气氛中的难熔过渡金属钛、钼和表面氮化，形成和组织致密的氮化层，用多种方法分析和表征了氮化层的化学成分和组织结构，激光的作用使得金属表面熔化和氮气激活，导致液相氮化反应，激光引起的加热熔化和激波效应同时使表层组织致密。     

脉冲激光诱导钛表面氮化的研究

介绍了在氮气气氛下,用脉冲激光照射钛表面实现钛的诱导氮化的实验结果.利用扫描电镜(SEM)、X射线衍射(XRD)和拉曼光谱对氮化表面进行了结构表征和性能分析.X射线衍射(XRD)结果显示氮化层的主要成分是a-Ti相和δ-TiN相,同时含有少量的a-Ti(N)固溶体.随着激光平均功率的增加,氮化层中δ-TiN相和α-Ti(N)固溶体含量逐渐增加,相应的氮含量也逐渐增加.纳米硬度测试结果显示氮化层的纳米硬度和弹性模量较基材钛明显增加,2mN载荷下测得氮化层的纳米硬度和弹性模量分别在11.5～15GPa和200～250GPa之间.     

40CrNiMoA钢激光淬火+氮化复合处理

对40CrNiMoA钢分别经激光淬火、气体氮化、氮化-激光淬火复合处理及激光淬火-氮化复合处理的硬化层深度及其表面硬度分布进行了比较分析。结果表明，在激光淬火-氮化复合处理中，激光淬火可使随后氮化处理的表层硬度提高100-200HV，硬化层深度可成倍增加；在氮化-激光淬火复合处理中，激光淬火可使预先氮化处理的硬化层深度有大幅度的提高，而表层硬度变化不大。     

钛合金表面氮化技术研究进展

本文概述了近年来为了提高钛及钛合金表面耐磨性在钛合金表面制备氮化钛膜层而采用的表面处理技术。从气体氮化、液体氮化以及离子氮化三方面讨论了每种工艺方法所获表面改性层的结构和性能特征及其适应范围。     

气体催渗氮化工艺试验及其应用

在普通气体氮化炉中加入海绵钛、三氧化二铬、氯化铵作催化剂进行气体催渗氮化工艺试验。用金相显微镜观察了试样的金相组织;用维氏硬度计或表面洛氏硬度计测定了试样的表层硬度;用 x-射线结构分析仪和电子探针仪测定了渗层的相结构和成份。试验结果表明,表层已有微量钛渗入,因此提高了氮化层的硬度。我们初步试验了气体催渗工艺参数对渗层的影响,得出了催化剂的配方;与原有普通气体氮化相比,它具有表面硬度高、耐热和耐腐蚀性能好等优点,同时缩短氮化周期约3—4倍。经五年多的实际生产应用,氮化了各种精密零件,效果良好。     

工业纯铁等离子体氮化及Ti/TiN多层薄膜沉积复合处理研究

为改善工业纯铁的耐磨抗腐蚀性能,本文采用低偏压高频等离子浸没离子注入及氮化技术(HLPⅢ)对工业纯铁进行表面改性,然后利用非平衡磁控溅射技术(UBMS)在低压高频等离子浸没离子注入及氮化处理样品表面制备Ti/TiN多层膜.研究发现,工业纯铁在3.5kV脉冲电压(频率15.15kHz,占空比25%)下等离子注入及氮化3h后,表面形成了深度达4μm的氮化层,其相结构以ε-Fe_3N和γ-Fe_4N结构为主.等离子氮化及Ti/TiN多层薄膜沉积复合处理后,工业纯铁的硬度、耐磨损性能以及抗腐蚀性能均得到大大提高,等离子注入及氮化形成的氮化层有利于提高Ti/TiN多层薄膜与工业纯铁基体之间的结合力和耐磨性.     

NiTi合金低压等离子渗氮研究

采用低压等离子渗氮工艺对NiTi合金进行了渗氮处理.氮化处理后NiTi合金表面硬度升高.XRD测试结果表明在合金表面形成了一层TiN涂层,在TiN涂层下为Ni3Ti相.电化学腐蚀测试表明经氮化处理后合金的耐腐蚀能力大为提高.     

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。     

Laser Gas Nitriding of Ti-6AI-4V Alloy

Laser gas nitriding of Ti-6A1-4V has been investigated with both CO₂ and Nd:YAG lasers. Results indicate that Nd:YAG laser in pulse mode provides a better surface finish and a lower cracking severity than CO₂ laser. A crack-free nitrided layer has been obtained by optimizing the processing parameters. Titanium nitride (TiN) significantly increases the hardness of the nitrided surfaces. The amount of titanium nitride produced depends on the processing parameters, such as laser pulse energy and nitrogen concentration. With optimized parameters, the nitrided surface is somewhat rougher than the polished base metal but much smoother than the shot peened surface. The shrinkage effect in the laser melt zone produces surface residual tensile stresses regardless of the processing environment. Preheating or stress relieving after laser nitriding can significantly reduce the residual tensile stress level.     

The effect of laser surface nitriding with a spinning laser beam on the wear resistance of commercial purity titanium

Laser nitriding of commercial purity titanium using various concentrations of helium and nitrogen has been carried out. The surface appearance and microstructure of a treated layer were found to be dependent on the beam power density, interaction time, velocity and concentration of nitrogen. X-ray diffraction analyses have led to the conclusion that the dendrite layer in the resolidified zone of the nitrided specimens consisted mainly of TiN. The surface roughness of specimens after various laser treatments was investigated by SEM and a surface profilemeter. Using optical microscopy, the dendrite TiN and needle-like structure in the melt zone, and the large grain structure in the heat affected zone, were investigated. The surface wear resistance of nitriding CPTi was significantly improved compared to the untreated or laser glazed material, and the wear data were found to correlate with scanning electron microscopy observations. Two layers, having different microstructures, thickness and abrasive wear resistance were identified. Further, 100% overlapping considerably improved the wear resistance of the nitrided specimens.     

An investigation of nitrided layer prepared by direct current nitrogen arc discharge

A simple direct current (DC) nitrogen arc discharge method is presented, which allows for in situ nitriding of titanium at atmospheric pressure. The microstructure and microhardness of the nitrided layer and effects of the arc discharge current were investigated. The nitrided layer was mainly composed of TiN dendrites and small amounts of TiN_0.3. The density and size of the TiN dendrites gradually decreased from the surface towards the titanium substrate. The layer had a good adhesion with titanium. With an increase of the arc discharge current from 40 to 80 A, the TiN dendrites coarsened, the layer thickness and amount of TiN increased and the layer hardness enhanced. The nitrided layer with the highest hardness value of 1600 HV and thickness of 1800 μm was obtained for an arc discharge current of 80 A.     

氮氩混合比对TA2真空氮化层结构与性能的影响

采用间歇式真空氮化技术对TA2钛合金进行渗氮处理。探究氮氩混合比对合金氮化层结构和性能的影响规律。结果表明:表面渗氮层主要由TiN和TiN0.3相组成,氮氩比越低其有效硬化层越厚,但会降低有效活性N原子的相对含量,不利于渗层的致密性。适当的氮氩混合比能在TA2表面形成氮化物,N原子有效地向纵深扩散,氮化物层与扩散层结合紧密,过渡良好,硬度梯度平缓;腐蚀电位随着氮氩比的增加呈现逐渐上升趋势,从氮氩比为1∶5时的-0.622V提升到氮氩比为5∶1时的-0.549V,腐蚀电流和腐蚀速率则呈现出逐渐降低的趋势。     

不同温度下等离子渗氮后TC4钛合金的摩擦磨损性能EI北大核心CSCD

采用等离子渗氮技术提升TC4钛合金的耐磨性并探究最优渗氮温度。利用LDM 1-100型等离子渗氮设备,在650,700,750,800,850℃和900℃温度下对TC4钛合金进行渗氮处理,保温时间均为10 h。利用光学显微镜、扫描电子显微镜、白光三维形貌仪、X射线衍射仪和显微硬度计分别对不同温度渗氮试样的微观组织结构、表面形貌、表面粗糙度、相结构和硬度进行表征。利用CETR UMT-3型多功能摩擦磨损试验机测试等离子渗氮后TC4钛合金的摩擦学性能。结果表明:TC4钛合金表面显微硬度和粗糙度随温度升高而增大,在900℃渗氮后TC4钛合金表面显微硬度达到了1318HV 0.05,约为基体(360HV 0.05)的4倍。硬度的升高是由于渗氮后试样表面形成了硬质氮化物相(TiN和Ti2N相),且随着渗氮温度升高氮化物的含量增加。相较于低温渗氮(低于750℃)的试样,850℃和900℃渗氮试样的承载能力显著提升。与原始TC4试样相比,渗氮处理后试样的磨损体积显著降低。当渗氮温度为850℃时,试样磨损体积为未处理试样磨损体积的1.2%(1 N),3.0%(3 N)和62.2%(5 N),试样的耐磨性提升更为显著。     

Characterization of plasma nitrided pure titanium by X-ray absorption spectroscopy

To date, the exact nature of the plasma nitriding mechanism and the role of energetic particle bombardment are not well understood. The purpose of this work has been to obtain a more detailed knowledge about the evolution of the plasma nitrided surface layer as a function of the energy of the bombarding particles. Nitrided layers were produced at the surface of pure titanium specimens at various flux energies by Intensified Plasma-Assisted Processing (IPAP), a triode plasma technique developed in our laboratory. X-ray Absorption Near Edge Structure (XANES) spectroscopy and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy were used to characterize the local structure of the titanium nitride layers. Cross sections of the processed specimens were studied by Auger electron spectroscopy and electron microscopy. The results showed that increasing flux energy promotes the formation of a well-ordered TiN layer at the surface. Low flux energies produce significantly lower fractions of the TiN phase at the surface, as well as thinner nitrided layers. A structural model was suggested and quantitatively tested based on the XANES and EXAFS measurements.     

Laser Gas Nitriding of Ti-6Al-4V Part 2: Characteristics of Nitrided Layers

The characteristics of laser nitrided layers formed on Ti-6Al-4V are presented in this investigation. It has been determined that titanium nitride (TiN) is formed, which significantly increases the hardness of the nitrided surfaces. The amount of titanium nitride produced depends on the processing parameters such as laser pulse energy and nitrogen concentration. Nitrided layers are much smoother along the laser pass direction than perpendicular to this direction. The shrinkage effect in the laser melt zone produces surface residual tensile stresses in Ti-6Al-4V samples regardless of whether the processing environment is Ar, N₂, or a mixture of these gases. Pre-heating or stress relieving after laser nitriding significantly reduces the residual tensile stress level.     

Corrosion behavior of PIRAC nitrided Ti-6Al-4V surgical alloy

Hard titanium nitride (TiN) coatings were obtained on the surface of Ti-6Al-4V alloy using an original PIRAC nitriding method, based on annealing the samples under a low pressure of monatomic nitrogen created by selective diffusion of N from the atmosphere. PIRAC nitrided samples exhibited excellent corrosion resistance in Ringer's solution in both potentiodynamic and potentiostatic tests. The anodic current and metal ion release rate of PIRAC nitrided Ti-6Al-4V at the typical corrosion potential values were significantly lower than those of the untreated alloy. This, together with the excellent adhesion and high wear resistance of the TiN coatings, makes PIRAC nitriding an attractive surface treatment for Ti-6Al-4V alloy surgical implants.     

FACTORS CONTROLLING THE FATIGUE STRENGTH OF NITRIDED TITANIUM

Abstract— The factors affecting the fatigue strength of nitrided titanium were clarified. The fatigue strength depended strongly on the fracture strength of the compound layer formed on the surface by nitriding. We found a Hall-Petch relationship between the fatigue strength of nitrided titanium and the grain size. The findings indicated that the reduction in the fatigue strength by nitriding results from both the formation of the compound layer possessing low fracture strength and grain growth occurring from ordinary nitriding. Furthermore, low-temperature nitriding (620°C, 24 h) was proposed to suppress grain growth. This treatment method improved not only the wear resistance and the corrosion resistance but also the fatigue strength of titanium.     

纯铁及结构钢快速气体渗氮工艺及机理研究

研究了纯铁及38CrMoAlA钢分别在500℃、0~0.4MPa压力和510℃、0~0.5MPa压力条件下的氨气渗氮行为。提高渗氮压力可显著加速气体渗氮动力学过程,纯铁在500℃和0.4 MPa下气体渗氮处理5h后渗氮层厚度(1160μm)可同比达到常规渗氮层厚度(205μm)的5倍以上,而38CrMoAlA钢经510℃和0.5 MPa压力下渗氮5h后的渗氮层厚度(400μm)几乎与常规渗氮50h所得硬化层厚度(440μm)相当。同时,纯铁及38CrMoAlA钢渗氮层中ε-Fe2-3N与γ′-Fe4N的相比例、氮势及表层硬度均随压力的提高呈现先增加后降低的变化趋势。提出了一种合金结构钢表面高强高韧渗氮层快速复合制备工艺(增压渗氮+冷轧)。与一段式常规渗氮及增压渗氮工艺相比,复合工艺处理表层硬度及韧性均较优良,尤其高剪切应力磨损条件下复合处理表层的耐磨性能最优,在20~600℃热循环处理10~300次条件下复合处理表层的耐热疲劳性能最佳。研究了42CrMo钢在既定的渗氮周期内(6h)以NH3为介质,530℃及不同压力循环次数条件下的气体渗氮行为。在渗氮温度和总时间相同条件下,循环压力气体渗氮样品化合物层随压力循环次数的增加逐渐减薄,渗氮层整体厚度随压力循环次数的增加逐渐增加,同时渗氮表层韧性随压力循环次数的增加逐渐增强。