圆锥滚子形变强化表层的残余应力分布

用X射线衍射方法测定了形变强化圆锥滚子沿层深的残余应力分布、X射线半高宽和表面残余奥氏体量。结果表明,圆锥滚子强化表层存在残余压应力,残余压应力峰出现在距表面约200μm处,峰值随强化时间延长而增大,强化16 h达最大,此后则减小;强化过程中滚子表面及次表面X射线半高宽减小,约在50μm处有一极小值。     

Y-TZP/LZAS微晶玻璃功能梯度涂层残余应力的有限元分析

设计了Y-TZP/LZAS微晶玻璃功能梯度涂层,使用有限元软件分析了成分分布指数、梯度层数目和梯度层厚度等参数对涂层/基体界面残余热应力的影响。结果表明:功能梯度材料的最佳成分梯度指数为m=1;涂层最佳层数为3-5层;涂层最佳厚度为1-1.5 mm;涂层表层主要分布为径向压应力;在涂层/基体界面的边缘区域应力集中较为严重;涂层/基体界面处的径向应力、轴向应力和剪切应力与成分分布指数、梯度层数目和梯度层厚度有密切的关系。用涂搪法制备了梯度涂层,用X射线衍射法(XRD)测试了涂层表面残余应力,验证了有限元结果的准确性。     

等离子喷涂纳米结构与传统结构热障涂层的残余应力对比研究

热障涂层的残余应力是影响其服役寿研究不多.在45钢基体上,用超音速火焰喷涂NiCocrAlY打底层,再用大气等离子喷涂ZrO2-8%(质量分数)Y2O3(8YSZ)工作层,制备了纳米结构与传统结构2种类型的热障涂层(TBC).采用SEM、XRD对这2种涂层的粉末及涂层进行了组织结构分析,用纳米压痕仪测得了2种涂层的弹性模量.用X射线衍射应力测试仪测得了2种涂层的表层残余应力.结果表明:喷涂工艺参数相同条件下,对于打底层及工作层的厚度均相同的2种涂层,纳米结构热障涂层的表层残余应力比传统结构热障涂层约低24.7%;相同打底层的纳米结构热障涂层表层残余应力随着陶瓷层厚度增加而增加,陶瓷层厚度在240 um以下时,表层为残余压应力;厚度超过300 um时,表层为残余拉应力.最后提出了相应的物理力学模型.     

PVD法制备TiN涂层界面特征与摩擦磨损性能

采用物理气相沉积法在Cr12MoV钢基体上制备了TiN涂层,利用扫描电镜、能量色散谱、X射线衍射和轮廓仪对涂层形貌特征、化学元素、物相组成和表面粗糙度进行了表征,用划痕法测试其结合强度,并分析划痕法涂层失效过程.通过往复磨损试验考察了其摩擦磨损性能,对涂层磨损机理进行了讨论.结果表明,TiN涂层主要组成相为TiN,试样表面粗糙度Ra值为328.91nm,涂层表面显微硬度达到2100 ～ 2200 HV;涂层厚度约为5μm,与基材之间存在一定的混合界面,其界面结合强度为28.85 N;在干滑动磨损实验条件下摩擦系数为0.45～0.52,涂层具有优异的耐磨性,其磨损机制主要为磨粒磨损.     

再制造热喷涂层的残余应力与显微特征的对应关系

利用高效能超音速等离子喷涂(HEPS)、爆炸喷涂(DGS)和高速电孤喷涂(HVAS)三种热喷涂技术制备了不同厚度的Fe-Cr-B-Si和Fe-Cr-B-Si-Mo涂层,利用X射线应力测定仪测定了涂层表面残余应力,并得出表面残余应力与涂层厚度的关系曲线,进一步采用电解剥层法+X射线应力测定法研究了涂层应力沿厚度方向的分布...     

薄膜几种重要力学性能的评价

提出了一种利用X射线应力分析技术和应变电测法测量附着膜的等效应力——等效单轴应变、屈服强度和加工硬化指数的方法。利用该方法测得一种厚度为2．5μm的TiN膜的务件屈服点σ0，1和σ0．2分别等于4．2GPa和4．4GPa，加工硬化指数72为0．36；对于一种厚度为2．4μm的铜膜，得到σ0．1-328MPa，σ0．2—415MPa，n=0．62。利用无应变剥层技术逐层剥离薄膜，同时测量基片曲率半径的变化，由此测得了一种厚度为2．3μm的TiN膜的残余应力沿层深分布。用新建立的一种利用X射线应力分析法测量薄膜泊松比的技术，测出一种TiN膜的泊松比等于0．27。给出了测量陶瓷膜的杨氏模量的设想。     

Q235表面辉光等离子渗镀TiN耐蚀性研究

利用等离子辉光放电溅射技术,在碳钢表面复合渗镀形成TiN扩散层和沉积层.表面成分检测渗镀层呈梯度材料分布,表面钛原子和氮原子之比,符合TiN相结构.渗镀层总深度约有15μm,表层TiN约有4μm.渗镀层成分检测表明,与基体之间呈梯度分布.X射线衍射结果表明,渗镀层表面为TiN,其中(200)晶面的衍射峰最强,具有明显的择优取向.TiN复合层在H2S溶液中的腐蚀行为表明:辉光合成的TiN涂层可以提高材料在富液溶液中的耐蚀性能,与PVD沉积TiN试样和基体低碳钢试样相比耐蚀性分别提高了5.76,49.76倍.     

PVD法制备(Ti,Al)N涂层中残余应力对其质量的影响

在国产离子镀和空心阴极离子镀复合镀膜机上,通过改变脉冲偏压值制备了(Ti,Al)N涂层。用X射线衍射仪对涂层的相组成进行了检测分析,并通过测得的衍射谱线计算了(Ti,Al)N涂层中的残余应力值;扫描电镜观察涂层表面微观形貌显示涂层表面存在"大颗粒"现象;用材料表面微纳米力学测试系统检测了涂层与基体间的结合力和涂层的硬度值。对涂层中残余应力与质量和性能之间关系的研究分析表明:(Ti,Al)N涂层中存在着残余压应力,且随脉冲偏压值的增加其值有先减小后增大的趋势;涂层中"大颗粒"现象随脉冲偏压值的提高能够显著得到减轻,涂层与基体间结合力得到提高,涂层的硬度值增大,涂层质量和力学性能均得到改善。     

玻璃纤维表面化学镀Ni-P合金涂层的研究

采用化学镀工艺在玻璃纤维表面包覆一层Ni-P合金涂层,用扫描电子显微镜、X射线能谱仪、X射线衍射仪、热震实验对涂层的形貌、组成、结构和性能进行了表征.结果表明,玻璃纤维表面化学镀Ni-P合金涂层由直径为0.1～1μm的颗粒所组成,涂层厚度约为1～1.5μm.涂层与玻璃纤维之间的结合力好,电阻率达到1.25×10-3Ω·cm.化学镀玻璃纤维具有较好的导电性,可作为制备导电高分子材料的填料.     

射频磁控溅射法制备TiB2涂层及其性能分析

利用射频磁控溅射技术在硅和钢片上沉积了TiB2涂层.采用场发射电子扫描显微镜(FESEM),小掠射角x射线衍射(GAXRD)及X射线光电子能谱(XPS)分别研究了涂层的横截面形貌,晶体结构以及涂层中的元素和化学状态.同时,对涂层的显微硬度和残余应力进行了表征.结果表明, 利用射频磁控溅射法制备的TiB2涂层平整光滑,结构致密,沿[001]晶向择优生长,具有纳米晶结构,硬度显著提高,而且残余压应力较低.     

Influence of Substrate Negative Bias on Structure and Properties of TiN Coatings Prepared by Hybrid HIPIMS Method

TiN coatings were deposited using a hybrid home-made high power impulse magnetron sputtering(HIPIMS)technique at room temperature.The effects of substrate negative bias voltage on the deposition rate,composition,crystal structure,surface morphology,microstructure and mechanical properties were investigated.The results revealed that with the increase in bias voltage from-50 to-400 V,TiN coatings exhibited a trend of densification and the crystal structure gradually evolved from(111) orientation to(200)orientation.The growth rate decreased from about 12.2 nm to 7.8 nm per minute with the coating densification.When the bias voltage was-300 V,the minimum surface roughness value of 10.1 nm was obtained,and the hardness and Young's modulus of TiN coatings reached the maximum value of 17.4 GPa and 263.8 GPa,respectively.Meanwhile,the highest adhesion of 59 N was obtained between coating and substrate.     

Effect of heating on the residual stresses in TiN films investigated using synchrotron radiation

The structure and residual stresses of TiN films deposited by arc ion plating (AIP) on a steel substrate were investigated using a synchrotron radiation system that emits ultra-intense X-rays. In a previous study, the crystal structures of TiN films deposited by AIP were found to be strongly influenced by the bias voltage. When high bias voltages were used, TiN films that were approximately 200 nm thickness had a preferred orientation of {110}, whereas TiN films that were approximately 600 nm thickness has a multilayer film orientation of {111}/{110}. In this present study, the two-tilt method was used to evaluate the residual stresses in TiN films by measuring lattice strains in two directions determined by the crystal orientation. Residual stresses in 600-nm-thick as-deposited TiN films were found to be −10.0 GPa and −8.0 GPa for {111}- and {110}-textured layers, respectively, while they were −8.0 GPa for {110}-textured layers in 200-nm-thick as-deposited TiN films. Residual stresses of both films relaxed to thermal stress levels upon annealing.     

Evaluation of Hard TiN Coatings by Depth Sensing Indentation and Scratch Testing Methods

The IAR Nanomechanical Probe (NMP) was used in the depth sensing indentation mode to evaluate the Vickers hardness (HV) and elastic modulus E of five commercial TiN coatings applied to a 17-4 PH stainless steel substrate. The HV values of the TiN layers at depth to thickness (DTT) ratios of less than 0.1 varied between about 28 and 39 GPa, depending on the deposition process. The elastic modulus was within the range of 300 to 400 GPa, corresponding to published values, at DTT ratios of less than or equal to 0.05. At higher DTT values, the elastic modulus decreased with increasing DTT ratio due to larger and larger interference from the less rigid stainless steel substrate. Depth sensing scratch tests were also performed on the samples to determine the critical load _crvalues needed to cause spallation of the coatings. For each coating, the interfacial fracture toughness K_ic was calculated from _crand used to describe the adhesive strength. Distinct differences between the K_ic values of the different samples were observed, reflecting differences in adhesive strength. The significance of these results is discussed in terms of the application of titanium nitride coatings to gas turbine engines.     

Alteration of internal stresses in SiO2/Cu/TiN thin films by X-ray and synchrotron radiation due to heat treatment

A break of wiring by stress-migration becomes a problem with an integrated circuit such as LSI. The present study investigates residual stress in SiO₂/Cu/TiN film deposited on glass substrates. A TiN layer, as an undercoat, was first deposited on the substrate by arc ion plating and then Cu and SiO₂ layers were deposited by plasma coating. The crystal structure and the residual stress in the deposited multi-layer film were investigated using in-lab. X-ray equipment and a synchrotron radiation device that emits ultra-high-intensity X-rays. It was found that the SiO₂ film was amorphous and both the Cu and TiN films had a strong {1 1 1} orientation. The Cu and TiN layers in the multi thick (Cu and TiN:1.0 μm)-layer film and multi thin (0.1 μm)-layer film exhibited tensile residual stresses. Both tensile residual stresses in the multi thin-layer film are larger than the multi thick-layer film. After annealing at 400 °C, these tensile residual stresses in both the films increased with increasing the annealing temperature. Surface swelling formations, such as bubbles were observed in the multi thick-layer film. However, in the case of the multi thin-layer films, there was no change in the surface morphology following heat-treatment.     

Residual stress, Young''s modulus and fracture stress of hot flame deposited diamond

Chemical vapour deposition (CVD) diamond coatings deposited on various substrates usually contain residual stresses. Since the residual stress affects the adhesion of the coating to the substrate, as well as the performance of the coating/substrate composite in many technical applications it is of importance to study the magnitude of these stresses.

In the present study the hot flame method was used to deposit diamond coatings on cemented carbide inserts by scanning the surface with a nine flame nozzle. By varying the oxygen to acetylene flow ratio and the deposition time coatings of different qualities and thicknesses were obtained. The residual strain/stress of the coatings was measured by three different methods: X-ray diffraction using the sin² (Ψ) method, Raman spectroscopy and disc deflection measurements. To extract the residual stress from the strain data the Young's modulus was obtained from bending tests of diamond cantilever beams manufactured from free standing diamond films. The latter technique was also used to determine the fracture stress of the diamond films.

All deposited coatings displayed a residual compressive strain/stress state. The residual strain in the diamond coatings did not vary with coating thickness (1.5 μm to 20 μm) but was found to increase from −1.8 × 10⁻³ to −2.2 × 10⁻³ with decreasing diamond quality. The compressive residual stress was found to decrease from −2 GPa to −1.3 GPa with decreasing diamond quality. This is mainly due to a decrease in Young's modulus (from 1.1 TPa to 0.6 TPa) with decreasing diamond quality. Also the fracture stress was found to decrease (from 1.8 GPa to 0.8 GPa) with decreasing diamond quality. The three methods used for measuring the stress state in the coatings, X-ray diffraction, Raman spectroscopy and deflection measurement, all give the same result. The deflection technique has the advantage that no information about the elastic properties of the coating is needed, whereas Raman spectroscopy has the best lateral resolution (≈5 μm) and is the fastest method (≈5 min).     

界面梯度对TiN／不锈钢涂层应力的影响

气相沉积表面涂层在科学技术各领域得到广泛应用，然而，由于涂层与基体在化学和物理性质上的差异，使得涂层与基体在界面两侧产生结构和性能上的突变，影响了涂层功能的充分发挥。为此，采用多靶磁控溅射技术制备了具有梯度过渡层的ＴｉＮ／不多靶磁控溅射技术制备了具有梯度过渡层的ＴｉＮ／不锈钢涂层，并研究了梯度层对涂层内应力的影响。研究结果表明：采用多靶磁控溅射技术，分别控制各靶的功率，能够精确控制梯度层的成份变化     

Fatigue Resistance of an Anodized and Hardanodized 6082 Aluminum Alloy Depending on the Coating Thickness in the High Cycle Regime

In this study, the high cycle fatigue behavior of an anodized 6082 aluminum alloy is investigated. Main focus is on the most relevant influencing factors for crack initiation and propagation under cyclic loading and damage mechanisms considering coating type, thickness, and residual stresses. The bare substrate is compared to anodized and hardanodized specimens with three coating thicknesses, for each coating type, in the range from 20 to 70 μm. Coating hardness and microstructure as well as residual stresses are analyzed. Fatigue and fracture behavior under alternating tension–compression loading is determined. Dependent on the coating thickness, the fatigue strength is reduced by 8%–50% after anodizing and by 50%–62% after hardanodizing. As the coating thickness is equal to the initial crack length from a fracture mechanical point of view, stress intensities at the crack tips are higher for thicker coatings respectively longer initial crack lengths. Therefore, propagation of fatigue-induced cracks from the coating into the substrate is promoted for a higher coating thickness resulting in premature failure. A significant correlation between the coating thickness and tensile residual stresses induced by both coatings in the subjacent substrate is not found and residual stress influence on the overall fatigue strength is only minor.     

Microstructure, chemistry and coating properties of ion-plated TiN on type 304 stainless steel

Characterization of TiN coatings on type 304 stainless steel was carried out using a Zeiss EM 902A energy filtering transmission electron microscope equipped with an electron energy loss spectroscopy (EELS) detector. TiN thin films were produced by a hollow cathode discharge ion plating coater. It was found by plan-view transmission electron microscopy that the microstructure of the TiN coatings is thickness dependent. The grain size of TiN ranges from 88 nm at the coating surface down to 9 nm near the TiN/steel interface. In addition, the TiN surface layer shows some degree of texture, but the subsurface and internal TiN layers are mainly equiaxial and randomly oriented. Chemical analysis by EELS shows that the relative oxygen content increases linearly from the TiN surface to the TiN/steel interface, whereas the relative nitrogen content first decreases slowly and then drops rapidly near the interface. The presence of a Ti₂N phase and the deficiency of nitrogen near the TiN/steel interface suggest that the early-deposited TiN is nonstoichiometric. By the periodic cracking method, the ultimate shear stress at the TiN/steel interface and the residual stress in the TiN thin film were estimated to be 2.2 GPa and 12.8 GPa, respectively.     

Evaluation of PVD nitride coatings, using impact, scratch and Rockwell-C adhesion tests

In this work the scratch test, the impact test and the Rockwell-C adhesion test were compared by investigating the adhesion properties of three types of sputtered physical vapour deposition coatings: TiN, CrN and Cr₂N. Each coating type was deposited on polished SAE 52100 steel, with different thicknesses in the nominal range of 2–20 μm, to evaluate the thickness influence on the test results. All the tests showed a ductile behaviour for the TiN coating with small delaminations and a brittle behaviour for the CrN and Cr₂N coatings with relatively large delaminations. An increase of the dimensions of the delaminations with increased coating thickness was detected for all layer types.

With the scratch test a significant increase in upper critical load with layer thickness was observed for all of the coatings. However, there was considerable variability especially for the Cr₂N coatings. The impact tests showed no coating failure for the TiN layer, and a decreasing impact crater volume with increasing layer thickness, whereas the CrN and Cr₂N layers failed after 10³ impacts and showed an increasing impact crater volume with increasing layer thickness.

The studies demonstrate the usefulness of using these test methods for differentiating between the behaviour of different coatings under various contact conditions.     

In situ synthesis of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy

The aim of this paper was to develop an in situ method to synthesize the TiN reinforced Ti₃Al intermetallic matrix composite (IMC) coatings on Ti6Al4V alloy. The method was divided into two steps, namely depositing pure Al coating on Ti6Al4V substrate by using plasma spraying, and laser nitriding of Al coating in nitrogen atmosphere. The microstructure and mechanical properties of TiN/Ti₃Al IMC coatings synthesized at different laser scanning speeds (LSSs) in laser nitriding were investigated. Results showed that the crack- and pore-free IMC coatings can be made through the proposed method. However, the morphologies of TiN dendrites and mechanical properties of coatings were strongly dependent on LSS used in nitriding. With decreasing the LSS, the amount and density of TiN phase in the coating increased, leading to the increment of microhardness and elastic modulus and the decrement of fracture toughness of coating. When the LSS was extremely high (i.e., 600 mm/min), only a thin TiN/Ti₃Al layer with thickness around of 100 μm was formed near the coating surface.