纯钛表面等离子渗镍合金层的显微组织及摩擦学性能

采用等离子表面合金化技术对纯钛进行表面渗镍处理,对渗镍后形成的合金层显微组织、物相组成及硬度进行了分析,并对其摩擦学性能进行了研究。结果表明:渗镍后在纯钛表面形成了与基体结合良好的钛-镍合金层,合金层主要由Ti2Ni、TiNi及钛相组成,厚约30μm,显微硬度约为570HV,合金层的干滑动摩擦磨损性能较纯钛基体的有很大提高。     

Ti2AlNb基合金等离子表面渗铬层组织结构对耐磨性能的影响

低硬度和较差的耐磨性制约了钛铝基合金在航空领域的应用。为了提高Ti2AlNb合金的表面硬度和耐磨性,采用双层辉光等离子表面合金化技术对Ti2AlNb合金表面进行渗Cr处理,并对其微观组织、扩散特性及显微硬度和耐磨性进行了分析测试。结果表明：经等离子渗铬处理后,可获得约25μm的合金层;渗层中Cr含量随渗层深度有显著变化且在高温条件下因各原子扩散能力的差异,以基体中Al和Nb量的变化为主,在渗层的不同区域形成不同的相,表层以含Cr2Nb的Laves相和Al8Cr5相为主,而在渗层和基体的交界处形成新的无序O相（Ti25.36Al18.44Nb）;渗层硬度值由外层的HV1125逐渐过渡到基体的HV432,渗层与基体的界面处由于无序O相的析出而硬度最低。渗Cr处理将合金的摩擦因数由原来的0.24降低到0.15,磨损率降低了60%以上。     

预氮化对碳素工具钢560℃双辉等离子渗铬的影响

为了降低双辉等离子渗铬的工艺温度,提高低温渗铬速度,对T10钢表面在550℃进行不同时间的离子预氮化处理,再进行560℃×4h低温双辉等离子渗铬,对渗层的组织与硬度进行了研究.结果表明:各种条件下渗铬后,表面均形成铬的沉积层 扩散层,沉积层厚度4~5μm,组织致密,与基体结合良好;扩散层铬含量与显微硬度随预氮化时间的增加而增加,且均呈梯度分布;未经预氮化处理试样的扩散层深20μm左右,表面物相为铁、铁-铬固溶体、铬碳化物(Cr7C3,Cr23C6),表面显微硬度约700HV;预氮化后试样的扩散层深25~30μm,表面物相主要为铬、铁-铬固溶体、铬碳化物(Cr7C3,Cr23C6)、铬氮化物(CrN),显微硬度达915~1250HV,较未预氮化的试样提高45%以上.     

电火花强化WC92Co8复合层界面行为研究

利用电火花强化技术在合金表面沉积WC92Co8强化层,能够有效改善基体表面性能。采用Ti合金、45钢为基体材料,研究了WC92Co8强化层与基体间的界面行为。认为电火花强化技术可在金属基体表面制造高熔点材料强化层。其中Ti合金强化层表面由TiC相、W_2C相和少量的W组成。显微硬度达到1129 HV,强化层厚度大于50μm。Ti合金表面性能发生质的变化。     

钼基高温合金表面包埋渗法制备渗铝层的组织与性能

采用包埋渗法在TZM钼基高温合金表面制备抗氧化的渗铝层,渗铝温度为1 050℃,渗铝时间为12 h;采用SEM、EDS和XRD等分析了渗层的显微组织、物相组成和元素分布等,并对渗层的硬度和抗高温氧化性能进行了研究。结果表明:渗层的相组成为Al_5Mo、Al_3Mo和Al_4Mo;渗层均匀致密,厚度达到130μm,具有双层结构,与基体形成了冶金结合;渗层表面呈颗粒状,其显微硬度达到了8 000 MPa;在800℃×80 h高温氧化下包埋渗铝层具有较好的抗氧化性能。     

双层辉光等离子渗金属技术制备TiN渗层及其耐NaOH溶液腐蚀性能

采用双层辉光等离子渗金属技术在Q235钢表面上制备了TiN渗层;对渗层的组织、硬度、成分和相结构及其耐NaOH溶液腐蚀性能进行了研究.结果表明:该渗层是由TiN颗粒均匀分布的扩散层及表面TiN沉积层组成的梯度结构;渗层表面形貌为胞状组织,颗粒致密均匀,表面为金黄色,渗层厚度可达16μm,与基体实现了冶金结合;渗层表面钛...     

钛合金表面激光熔覆镍-铬-硅复合涂层的显微组织和摩擦学性能

在Ti-5621s合金表面采用激光熔覆制备了镍-铬-硅复合涂层,分析了涂层的显微组织,测试了涂层的硬度和摩擦学性能.结果表明:复合涂层中以Ti5Si3和Cr3Si为主的颗粒增强相弥散分布在β-Ti和γ-Ni两相固溶体中;涂层的硬度较基体有显著的提高;由于金属硅化物Ti5Si3和Cr3Si的高硬度、强原子间结合力,该复合涂层明显地改善了基体合金的摩擦和磨损性能.     

TB8钛合金表面间歇式真空渗氮层的组织与性能

对TB8钛合金进行800℃间歇式真空渗氮6 h,研究了表面渗氮层的组织、硬度、耐磨性能及耐腐蚀性能.结果表明:TB8钛合金表面间歇式真空渗氮层主要由厚度60～80μm氮化物层和厚度110～130μm氮扩散区组成,表层物相包括TiN、TiN0.3、Ti2AlN及α-Ti,表层硬度为800～850 HV,由表层至心部硬度缓慢降低,心部基体的硬度为250～270 HV;在相同条件下,间歇式真空渗氮处理合金的磨损质量损失为未渗氮合金的1/12,表面形成了浅而窄的磨痕,耐磨性得到显著提高;间歇式真空渗氮处理合金在HF和HNO3混合溶液中的腐蚀速率仅为未渗氮合金的1/153,表面未见明显腐蚀坑,耐腐蚀性能得到明显提高.     

不同厚度电镀铬层的组织及性能

为了改善电镀厚铬层气密性差的现状,采用工厂现行的电镀工艺在基体表面制备不同厚度的铬层,研究了不同厚度铬层的表面内应力、硬度、晶粒大小和织构。结果表明:随着厚度的增加,铬层表面内应力呈波动性变化,且表面内应力均为拉应力;随着厚度的增加,铬层中的大尺寸晶粒增多,但平均晶粒尺寸变化不大,均为8.5μm左右;随着铬层厚度的增加,(110)晶面织构逐渐退化,(200)晶面织构逐渐增强;随着铬层厚度的增加,铬层硬度先缓慢增大,当铬层厚度由22.51μm增加到46.02μm时则迅速增大,随后又缓慢增大。     

ZG45铸钢表面Ni/ZrO_2复合铸渗层的组织与耐磨性能

采用负压铸渗技术在ZG45铸钢表面制备了Ni/ZrO_2复合铸渗层,并对其显微组织、硬度以及常温摩擦学性能进行了研究。结果表明:铸渗层的主要相组成为ZrO_2,Cr_2B,NiB化合物和Fe(Ni)固溶体相;其表面硬度可达60～64 HRC,显微硬度由铸渗层表面至基体呈梯度变化,最大硬度在铸渗层的次表层,最大值为8.5GPa;在100 N和250 N载荷下基体的磨损率分别是铸渗层的22.6倍和21.9倍。     

Thick rutile layer on titanium for tribological applications

In the present work, efforts have been made to oxidise the titanium surface, followed by very slow cooling to produce a thick and adherent oxide layer. The response of titanium to oxidation at various temperatures and timings has been investigated, in terms of layer thickness, phase evolution, surface morphology, oxide layer–substrate adhesion, hardness and tribological characteristics. A variety of experimental and analytical techniques, including X-ray diffraction, field-emission scanning electron microscopy, scanning electron microscopy, micro-hardness and tribological testing, have been used to characterise the resultant thermal oxidised surfaces. The results showed that a thick oxide layer with rutile TiO₂ and oxygen diffused Ti structure can be produced, which exhibited excellent adhesion with the titanium substrate, low friction and superior wear resistance during pin-on-disc sliding tests and thus good potential for tribological applications.     

Friction and Wear Properties of Graphite-Like Carbon Films Deposited on Different Substrates with a Different Interlayer Under High Hertzian Contact Stress

Four types of graphite-like carbon (GLC) films were deposited on different substrates (Ti6Al4V, WC-27CrNi) with a different interlayer (TiC/Ti, TiC/Ti/TiN) using an unbalanced magnetron sputtering system. The effect of substrate and interlayer on the microstructure and properties of the studied GLC films was then investigated using different characterization techniques. The results show that both the substrate and interlayer had an obvious influence on the tribological properties of the studied GLC films even though there was no significant structural difference between these films. Specifically, a substrate with a high hardness was propitious to achieving superior tribological behaviors for carbon film even with a different interlayer. However, the interlayer had a distinct influence on the tribological properties of the carbon film deposited on different substrates, and this effect varied with the hardness property of the substrate. For a hard substrate, the wear rate and wear life were similar irrespective of the interlayer. For a soft substrate, the addition of a TiN interlayer improved the wear life sevenfold compared to the film with only a TiC/Ti interlayer, but the wear rate for a film with and without a TiN interlayer was approximately the same. The obvious discrepancy between wear life and wear rate for a carbon film deposited on soft substrate was closely related with the film adhesion strength and plastic deformation of the substrate materials. Based on these results, it can be concluded that the wear life is a better parameter than wear rate in terms of characterization of the wear resistance of carbon film once the applied load causes the plastic deformation of the substrate.     

Enhancing tribological performance of Ti-6Al-4V by sliding process

The exceptional combination of mechanical, physical and anti-corrosive properties of Titanium alloy Ti-6Al-4?V (Ti64) makes it idle material for the applications like aerospace, automobile, chemical, medical etc. However, Ti64 exhibits poor tribological (friction and wear) properties, which limits its implementation in the intended applications. The tribological performance of the Ti64 can be enhanced by developing a protective layer or coating on its surface. It has been reported in literatures that through rubbing process the oxide layers can be achieved at much lower temperature compared to external heating process. Therefore, an endeavour is made in the present work to achieve a tribo-oxide protective layer on the surface of Ti64 through rubbing process. For this, at first the tribological behaviour of tribo pair: Ti64 pin-alumina disc is studied under dry ambient condition for diverse loading and sliding speed conditions, using pin on disc experimental set-up. The obtained results are compared with literatures. The tribological performance is quantified in terms of coefficient of friction (COF) and wear rate. To investigate the tribological mechanism and behaviour, in-situ analysis was performed on the pin’s surface using (i) scanning electron microscopy, and (ii) energy dispersive analysis of X-ray. The mechanical properties like nano-hardness and elastic modulus of the pins surface were also determined. It was envisaged that the tribological behaviour were extremely transient and depend greatly on what the surface has precisely experienced Based on the experimental observations, the experimental conditions providing (i) Case1: deprived tribological properties and (ii) Case 2: higher oxide layer is selected. Now, to enhance the tribological behaviour of Case 1, the pin with high oxide layer, i.e. Case 2 is used. For this experiment is performed initially for Case 2 conditions for the sliding distance of 1000 m (for developing oxide layer) and the experiment is continued for next 1000 m for Case 1 condition. The experimental results in terms of COF and wear rate are presented and corresponding enhancement in their values are discussed.     

Analytical transmission electron microscopy and electron diffraction for characterization of multiphase Ni-P-Ti surface layer on Ti-6Al-4V alloy

The microstructure, chemical and phase composition of the hard Ni‐P‐Ti layer formed on the Ti‐6Al‐4V alloy after duplex surface treatment were investigated by light microscopy, X‐ray diffraction, scanning electron microscopy and analytical/high‐resolution transmission electron microscopy. These investigations showed that the improved mechanical and tribological properties of the surface‐treated alloy were related to the presence of a multilayered microstructure containing several phases from the Ni‐Ti‐P‐Al system.     

Wear resistant multilayer nanocomposite WC1−x/C coating on Ti–6Al–4V titanium alloy

A significant improvement of tribological properties on Ti–6Al–4V has been achieved by developed in this study multilayer treatment method for the titanium alloys. This treatment consists of an intermediate 2 μm thick TiC_xN_y layer which has been deposited by the reactive arc evaporation onto a diffusion hardened material with interstitial O or N atoms by glow discharge plasma in the atmosphere of Ar+O₂ or Ar+N₂. Subsequently, an external 0.3 μm thin nanocomposite carbon-based WC_1−x/C coating has been deposited by a reactive magnetron sputtering of graphite and tungsten targets. The morphology, microstructure, chemical and phase compositions of the substrate material after treatment and coating deposition have been investigated with use of AFM, SEM, EDX, XRD, 3D profilometry and followed by tribological investigation of wear and friction analysis. An increase of hardness in the diffusion treated near-surface zone of the Ti–6Al–4V substrate has been achieved. In addition, a good adhesion between the intermediate gradient TiC_xN_y coating and the Ti–6Al–4V substrate as well as with the external nanocomposite coating has been obtained. Significant increase in wear resistance of up to 94% when compared to uncoated Ti–6Al–4V was reported. The proposed multilayer system deposited on the Ti–6Al–4V substrate is a promising method to significantly increase wear resistance of titanium alloys.     

A study on the influence of laser power on microstructural evolution and tribological functionality of metallic coatings deposited on Ti-6Al-4V alloy

Metallic Ti–Co binary coatings were fabricated on titanium alloy (Ti–6Al–4V) substrate by laser surface cladding technique using a continuous wave RofinSinar 4 kW Nd: YAG laser. The influence of laser power on microstructure, hardness and tribological performance of Ti–Co laser clad coatings on titanium alloy (Ti–6Al–4V) was examined. Laser powers of 750 and 900 W were varied with constant scan speed of 1.2 m/min. A beam size of 3 mm and argon shield gas flow rate of 1.2 L/min were set as the operating laser parameters. Phase identification and morphological studies of the coatings were carried out using X-ray diffractometry (XRD) and scanning electron microscopy (SEM), respectively. Based on the results of laser process optimisation, it was observed that both laser powers produced clad coatings with good metallurgical bond with no cracks or pores in the coatings. With respect to the substrate (Ti–6Al–4V), the microstructure, hardness and friction/wear behaviour of Ti–Co coatings on Ti–6Al–4V substrate were enhanced obviously.     

挤压轮表面PCVD法制备T(iCN)涂层组织与性能

通过挤压轮的失效形式分析,表面裂纹是引起其失效的主要原因。应用PCVD法对挤压轮(H13)进行表面改性处理,在其表面备制了一层T(iCN)涂层。通过扫描电镜观察T(iCN)涂层表面的形貌以及断口组织形貌,用EDS对其化学元素进行能谱分析,测试了T(iCN)涂层表面显微硬度和粗糙度。结果表明T(iCN)涂层中所含Ti元素的质量和原子百分比为最多,涂层界面结合良好,其表面硬度为1004HV,粗糙度为1.23μm,有利于改善其疲劳性能和延长使用寿命。     

甘油润滑下CrCN涂层的超低摩擦特性

为开发与CrCN涂层具有良好配伍润滑性能的绿色润滑剂,使用磁控溅射技术在304不锈钢表面沉积CrCN涂层,利用场发射扫描电子显微镜、原子力显微镜、纳米压痕仪、维氏硬度计、X射线衍射仪、X射线光电子能谱仪分别对其表面形貌、涂层厚度、力学性能、物相组成以及元素化学价态进行分析,并借助多功能摩擦磨损试验机评价在甘油润滑下CrCN涂层的摩擦学性能,并与PAO6润滑下结果进行比较。利用磁控溅射技术在不锈钢表面构筑的CrCN涂层表面光滑致密,粗糙度仅为1.01 nm,硬度可达14.39 GPa。对比钢-钢和钢-CrCN体系的摩擦学性能发现,钢-CrCN体系在甘油润滑下展现出优异的润滑性能;当负载为0.5 N时,钢-CrCN体系在甘油润滑下的摩擦因数可低至0.01,大大低于PAO6润滑下的摩擦因数。对磨痕的XPS分析表明,在摩擦过程中,甘油发生摩擦化学反应,在CrCN涂层的接触表面生成一层FeOOH层,甘油分子及其降解产物可能进一步吸附在FeOOH层,形成流体润滑层,有效降低了摩擦和磨损。     

Nd:YAG laser alloying of high-speed steel tools with BN and Ti/BN and the effects on turning performance

A 400 W pulsed Nd:YAG laser was used to surface alloy BN and Ti/BN on AISI M2 steel using hexagonal BN powder and Ti foil (25 μm thickness). The clearance (flank) faces of the single-point tool were laser alloyed using BN and Ti/BN. Optical metallography, scanning electron microscope, Vicker's microhardness and X-ray diffraction were employed to characterize the alloyed layers. The depths of the laser-alloyed zones of BN- and Ti/BN-alloyed tools were about 140 μm and 260 μm respectively. The hardness of the laser-alloyed layer with BN was about 640 HV while that of the alloyed layer with Ti/BN was about 680 HV. The alloyed layers were free from cracks and porosity. Both the alloyed and unalloyed tools were then tested on a 14.7 kW engine lathe to turn AISI 1045 steel workpieces. The results indicated that the tool life of BN-alloyed tools was about 200% higher than that of the unalloyed tools, while the tool life of Ti/BN-alloyed tools was about 260% higher when the tool life criterion was chosen as 0.3 mm flank wear. Also, the tool wear rate was reduced by about 30% and 50% for BN-and Ti/BN-alloyed tools, respectively. The reduction in tool wear of the alloyed tools was attributed to a reduction of the chip-tool contact length (and consequently the reduction of coefficient of friction between the tool and workpiece material) and to the different chip formation mechanisms.