316L不锈钢基材功能梯度Al涂层残余热应力分析

涂层材料的功能性和可靠性在很大程度上受残余热应力的影响,为降低残余热应力防止涂层开裂以及提高其热机械性能,利用有限元方法对Al/316L系梯度功能材料在制备过程中产生的残余热应力分布进行分析,详细讨论了成分分布指数、涂层厚度和梯度层数目对应力大小和分布的影响.分析结果表明成分分布指数的增大不但影响涂层和基体界面的应力大小,还影响涂层中热应力峰值所处位置;涂层残余应力随着梯度层厚度的增加而减小;梯度层数的增多,有利于涂层中残余热应力的缓和,但当梯度层数达到9时,缓和效果并不明显.     

316L不锈钢表面双层辉光离子渗金属技术制备Al2O3涂层

Al2O3涂层由于具有较好的阻氚渗透效果可用作聚变堆第1壁涂层.利用双层辉光离子渗金属技术在316L不锈钢表面进行渗Al后热氧化处理,得到了致密的Al2O3涂层.对渗Al层的成分和形貌分别利用X射线衍射分析仪和扫描电子显微镜进行了分析和观察.结果表明:双层辉光离子渗金属技术能够制备出均匀致密、与基体结合良好的渗Al层.在316L不锈钢表面渗Al的最佳工艺参数条件下,获得的渗Al层经随后的热氧化处理,可形成质量良好的致密Al2O3涂层.     

双层辉光离子渗金属技术制备Al-Cr-Si氧化物阻氚涂层

本文采用双层辉光离子渗金属技术在316L不锈钢表面进行Al-Cr-Si共渗后氧化处理,制备致密的氧化物阻氚渗透涂层。用SEM、TEM和XRD分析制备涂层的组织结构,用划痕法和抗热震实验对其进行性能测试。结果表明,Cr、Si元素的掺入使涂层生成连续致密的Al2O3氧化膜;在外层富铝区,Al2O3和少量Fe、Cr的氧化物反应生成了尖晶石型复合氧化物Fe(AlCr)2O4。氧流量为0.01L/min时制得的氧化涂层的组织和性能最佳,其结合力达68N,热震实验后表面无裂纹出现。     

CLAM钢基体表面Al2O3功能梯度涂层残余应力模拟分析

在ITER中国液态锂铅测试包层模块设计中拟采用Al2O3作为防氚渗透耐蚀绝缘涂层,为了防止涂层与CLAM钢基体间由于材料热膨胀不匹配而开裂失效,采用热应力缓和型功能梯度涂层。利用有限元分析软件ANSYS研究了Al2O3/CLAM钢系功能梯度涂层的残余应力分布。模拟结果表明,当成分分布指数p=0.8、层数N=6、梯度层厚度为H=0.6 mm时,应力缓和效果最优。此分析结果可为该涂层制备工艺的优化提供理论指导。     

聚变堆第一壁涂层材料TiC和TiN的残余应力研究

采用Ｘ衍射法测定了聚变堆第一壁涂层材料ＴｉＣ和ＴｉＮ薄膜的残余应力．对涂层材料不同的制备方法（化学气相沉积ＣＶＤ和物理气相沉积ＰＶＤ）、基体材料（Ｍｏ、石墨和３１６ＬＳＳ）、涂层厚度及沉积温度对残余应力的影响进行了研究．结果表明，ＣＶＤ与ＰＶＤ制备的涂层的残余应力均为压应力，且ＣＶＤ较ＰＶＤ产生的残余应力要低，Ｔｉ／Ｍｏ（ＣＶＤ）随涂层厚度（１４μｍ～６０μｍ）的增加，残余应力增加．ＰＶＤ涂层的残余应力主要为本征应力，高达数ＧＰａ．其值随沉积温度（２００℃～６５０℃）的升高而降低．对残余应力产生的原因作了初步讨论     

添加Al2O3和SiO2的大晶粒UO2芯块制备研究

研究了Al2O3和SiO2添加剂对UO2芯块晶粒尺寸的影响.结果表明:加入少量的Al2O3和SiO2,可有效促进烧结过程中UO2芯块的晶粒度长大,过量加入则会阻碍烧结过程中UO2芯块的致密化;在添加量一定的情况下,添加不同比例的Al2O3和SiO2,对芯块晶粒尺寸有较大影响,只添加SiO2,对芯块晶粒尺寸影响不大,Al2O3添加量增加,芯块晶粒尺寸随之增加;添加Al2O3和SiO2促进UO2芯块晶粒长大的机制是在烧结期间发生了液相烧结.     

添加Al2O3和SiO2的大晶粒UO2芯块制备研究

研究了Al2O3和SiO2添加剂对UO2芯块晶粒尺寸的影响.结果表明加入少量的Al2O3和SiO2,可有效促进烧结过程中UO2芯块的晶粒度长大,过量加入则会阻碍烧结过程中UO2芯块的致密化;在添加量一定的情况下,添加不同比例的Al2O3和SiO2,对芯块晶粒尺寸有较大影响,只添加SiO2,对芯块晶粒尺寸影响不大,Al2O3添加量增加,芯块晶粒尺寸随之增加;添加Al2O3和SiO2促进UO2芯块晶粒长大的机制是在烧结期间发生了液相烧结.     

316L不锈钢表面双层辉光离子渗金属技术制备Cr2O3涂层

为改善不锈钢的阻氚渗透性能,采用双层辉光离子渗金属技术在316L不锈钢表面渗铬渗氧制备出了氧化铬涂层,对涂层的组织特征、相组成和合金元素成分分布及渗入机理进行了分析.结果表明,渗铬后表面主要形成Cr的沉积层和Cr在α-Fe中的固溶体相,渗层厚度可达21 μm,铬含量最高可达92%,且由表及里呈梯度分布;随后对渗铬层进行渗氧处理,表面形成以Cr2O3为主的陶瓷层,其有效厚度约为45 μm,渗层与基体结合牢固.     

中子吸收涂层/斩盘界面应力的有限元分析

中子吸收涂层/斩盘界面的结合强度直接影响转盘式中子斩波器的性能。本文基于有限元计算软件ANSYS,对高速离心载荷下中子吸收涂层/斩盘界面的应力分布进行计算分析,考察涂层的弹性模量、泊松比、涂层厚度等参数对界面应力分布的影响。结果表明,采用软而韧的涂层可有效降低涂层/斩盘界面的应力峰值;减小涂层厚度有助于避免高速离心载荷下斩盘开口处的塑性破坏。     

钼合金基体等离子喷涂Al_2O_3涂层研究

本工作研究了钼合金作为基体等离子喷涂Al2O3的喷涂工艺,并对喷涂样品进行了分析。其中,基体材料钼合金的尺寸为φ26mm×10mm,涂层材料为99%的高纯Al2O3粉末,粒度为10～30μm。试样端面喷砂活化处理之后进行等离子喷涂。试验采用有底层和无底层两种喷涂方式,涂层厚度为0.25mm。分别对涂层的金相组织、孔隙率、硬度和结合强度进行测试。结果表明,有底层涂层样品的结合强度为5MPa左右,无底层的结合强度为17MPa,观察到底层与基体结合处产生裂纹导致强度偏小。Al2O3涂层的孔隙率随着喷涂距离的增大而增大,显微硬度和结合强度相反则随着喷距…     

Simulation of the effects of different substrates,temperature,and substrate roughness on the mechanical properties of Al_2O_3 coating as tritium penetration barrier

Residual thermal stress in the system is a serious problem that affects the application of tritium permeation barrier coatings in fusion reactors. The stress not only determines the adhesion between coating and substrate, but also changes the properties of the material. In this study,finite element analysis was used to investigate the relationship between the residual thermal stress and the mechanical properties of Al_2O_3 tritium penetration barrier systems. Moreover, the residual thermal stress influenced by factors such as different substrates, temperature, and substrate roughness was also analyzed. The calculation showed that the hardness and elastic modulus increased with increasing compressive stress. However, the hardness and elastic modulus decreased with increasing tensile stress. The systems composed of Al_2O_3 coatings and different substrates exhibited different trends in mechanical properties. As the temperature increased, the hardness and the elastic modulus increased in an Al_2O_3/316 L stainless steel system; the trend was opposite in an Al_2O_3/Si system.Apart from this, the roughness of the substrate surface in the system could magnify the change in hardness and elastic modulus of the coating. Results showed that all these factors led to variation in the mechanical properties of Al_2O_3 tritium permeation barrier systems. Thus, thedetailed reasons for the changes in mechanical properties of these materials need to be analyzed.     

Simulation of thermal stress in Er2O3 and Al2O3 tritium penetration barriers by finite-element analysis

The physical vapor deposition method is an effective way to deposit Al2O3 and Er2O3 on 316L stainless steel substrates acting as tritium permeation barriers in a fusion reactor.The distribution of residual thermal stress is calculated both in Al2O3 and Er2O3 coating systems with planar and rough substrates using finite element analysis.The parameters influencing the thermal stress in the sputter process are analyzed,such as coating and substrate properties,temperature and Young's modulus.This work shows that the thermal stress in Al2O3 and Er2O3 coating systems exhibit a linear relationship with substrate thickness,temperature and Young's modulus.However,this relationship is inversed with coating thickness.In addition,the rough substrate surface can increase the thermal stress in the process of coating deposition.The adhesive strength between the coating and the substrate is evaluated by the shear stress.Due to the higher compressive shear stress,the Al2O3 coating has a better adhesive strength with a 316L stainless steel substrate than the Er2O3 coating.Furthermore,the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.     

Vacuum plasma-sprayed tungsten on EUROFER and 316L: Results of characterisation and thermal loading tests

Vacuum plasma-spraying (VPS) can be used for the industrial deposition of thick W coatings on actively water-cooled components made of low activation steel or stainless steel. Mock-ups made of martensitic steels, EUROFER and F82H, as well as steel 316L, were coated with 2 mm thick W-VPS layers. The coated materials are candidates for first wall components (ITER and DEMO) receiving moderate heat load of up to 1 MW/m². Mixed tungsten/steel interlayers were applied to reduce the residual and thermal stresses at the substrate–coating interface and to improve the adhesion of the coating. The advantage of this mixed interlayer is that no further (high activation) materials have to be introduced to improve coating adhesion.The characterisation of the W-VPS layers includes the evaluation of the coating microstructure, the measurement of physical and mechanical properties and the metallographical examination before and after heat load tests.Heat load tests with steady state operation up to 2.5 MW/m² and cycling heat loads of 2 MW/m², were successfully completed. They confirm the thermomechanical suitability of industrially manufactured W-VPS coatings for plasma facing first wall components made of steel.     

Plasma Modified Polypropylene Membranes as the Lithium-Ion Battery Separators

To reduce the thermal shrinkage of the polymeric separators and improve the safety of the Li-ion batteries,plasma treatment and plasma enhanced vapor chemical deposition（PECVD）of SiO_x-like are carried out on polypropylene（PP）separators,respectively.Critical parameters for separator properties,such as the thermal shrinkage rate,porosity,wettability,and mechanical strength,are evaluated on the plasma treated PP membranes.O₂ plasma treatment is found to remarkably improve the wettability,porosity and electrolyte uptake.PECVD SiO_x-like coatings are found to be able to effectively reduce the thermal shrinkage rate of the membranes and increase the ionic conductivity.The electrolyte-philicity of the Si Ox-like coating surface can be tuned by the varying O₂ content in the gas mixture during the deposition.Though still acceptable,the mechanical strength is reduced after PECVD,which is due to the plasma etching.     

The formation of tritium permeation barriers by CVD

The effectiveness as permeation barriers of the following CVD coatings have been investigated: TiC (1 to 2 μm in thickness); a bi-layer of TiN on TiC (3 μm total thickness) and CVD A1₂O₃ on a TiN/TiC bi-layer. The substrate materials were TZM (a Mo alloy) and 316L stainless steel in the form of discs of diameter 48 mm and thickness 0.1 or 1 mm. Permeation measurements were performed in the temperature range 515–742 K using deuterium at pressures in the range 1–50 kPa. CVD layers were shown to form reasonably effective permeation barriers. At a temperature of 673 K TiC is around 6000 times less permeable to deuterium than 316L stainless steel.     

Numerical simulation of the combined effects of plasma heating and neutron heating loads on the ITER first wall

To understand the combined effect of plasma heating and neutron heating loadings, the distributions of temperature, stress, and strain in different two-dimensional first wall panel models under normal ITER operation condition were simulated using finite element method. The maximum temperature occurs at the Be armor, and reaches 461 °C. High thermal stresses (in the range of 80-200 MPa) are found at the interface between the Be armor and the CuCrZr layer. The maximum thermal stress reaches 324 MPa in the SS316L cooling tube (20 mm diameter), exceeding its yield strength and resulting in a maximum strain of about 1.7% at the tube inner surface. These simulation results are useful for the design and operation of ITER.     

Evaluation of stainless steel pipe cracking: Causes and fixes

This paper discusses (1) studies of impurity effects on susceptibility to intergranular stress corrosion cracking (IGSCC), (2) intergranular crack growth rate measurements, (3) finite-element studies of the residual stresses produced by induction heating stress improvement (IHSI) and the addition of weld overlays to flawed piping, (4) leak-before-break analyses of piping with 360° part-through cracks, and (5) parametric studies on the effect of through-wall residual stresses on intergranular crack growth behavior in large diameter piping weldments. The studies on the effect of impurities on IGSCC of Type 304 stainless steel show a strong synergistic interaction between dissolved oxygen and impurity concentration of the water. Low carbon stainless steel (Type 316NG) appear resistant to IGSCC even in impurity environments. However, they can become susceptible to transgranular SCC with low levels of sulfate or chloride present in the environment. The finite-element calculations show that IHSI and the weld overlay produce compressive residual stresses on the inner surface, and that the stresses at the crack tip remain compressive under design loads at least for shallow cracks.     

Synthesis of Nano-Size AlN Powders by Carbothermal Reduction from Plasma-Assisted Ball Milling Precursor

Nano-size aluminum nitride(AlN) powders have been successfully synthesized with a high efficiency method through annealing from milling assisted by discharge plasma(p-milling)alumina(Al_2O_3) precursors. The characterization of the p-milling Al_2O_3 powders and the synthesized AlN are investigated. Compared to conventional ball milling(c-milling), it can be found that the precursors by p-milling have a finer grain size with a higher specific surface area,which lead to a faster reaction efficiency and higher conversion to Al N at lower temperatures. The activation energy of p-milling Al_2O_3 is found to be 371.5 kJ/mol, a value that is much less than the reported value of the unmilled and the conventional milled Al_2O_3. Meanwhile, the synthesized Al N powders have unique features, such as an irregular lamp-like morphology with uniform particle distribution and fine average particle size. The results are attributed to the unique synergistic effect of p-milling, which is the effect of deformation, fracture, and cold welding of Al_2O_3 powders resulting from ball milling, that will be enhanced due to the introduction of discharge plasma.     

Crack propagation behavior by thermal fatigue around DSCu/SS316 HIP bonded interface

Hot Isostatic Pressing bonded (HIPed) structure of DSCu/SS316 is proposed for the first wall (FW) of ITER. In this report, the thermal fatigue crack propagation behavior around HIPed interface is investigated with DSCu/SS316 HIPed plate as a specimen which has an initial crack on DSCu side. In addition, numerical analysis is carried out to clarify the mechanism of the interfacial crack propagation and to evaluate crack propagation rate with fracture mechanics. It is concluded that the crack which was propagated very close to HIPed interface did not penetrate into SS316 and changed its propagation direction from perpendicular to parallel to HIPed interface. The interfacial crack is propagated by residual stress in combined mode.