Y-TZP/LZAS微晶玻璃功能梯度涂层残余应力分析

为了提高钢基体微晶玻璃涂层的韧性,设计了Y-TZP/LZAS微晶玻璃功能梯度涂层。运用有限元软件,分析了梯度层数目、梯度层厚度和层间3Y-TZP体积组分差等参数对涂层/基体界面残余热应力的影响。结果表明,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以及梯度层数目、梯度层厚度和3Y-TZP体积组分差均有密切关系。最后通过涂搪法制备了梯度涂层,测试了涂层表面残余应力,并与有限元结果对比,以验证模拟的准确性。     

涂层基体条件对梯度涂层残余应力影响研究

采用有限元法，对结构一定的Al/Ni-ZrO2梯度涂层在基体条件改变时涂层的残余应力进行了分析，结果表明，基体材料的热膨胀系数对涂层的残余应力有显著的影响，对于基体为圆柱形的涂层，其基体与涂层界面的残余应力梯度，最大轴向拉应力均随热膨胀系数的增大而线性增大，表面纯陶瓷层与次层界面残余应力梯度则随之减小，增大基体的直径和厚度，可缓和涂层残余应力，并在基体直径为36mm,厚度为20mm时各残余应力基本稳定。     

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。     

C涂层对SiC纤维增强Ti基复合材料界面的影响

采用透射电镜和扫描电镜研究了SiC纤维增强Ti基复合材料的界面反应,重点分析了C涂层对界面行为的影响.结果表明,C涂层可以明显改善纤维和基体之间的界面结合状况;SiC/C/Ti-6Al-4V复合材料的界面反应产物是主要为TiC,而无C涂层SiC/Ti-6Al-4V的界面反应产物为TiC,Ti5Si3和Ti3SiC2界面反应层生长受扩散控制,其厚度增长满足抛物线生长规律,SiC/C/Ti-6Al-4V由于C涂层消耗完毕前后的不同情况,其界面反应层生长并不完全符合这一规律,C涂层的存在可以有效的抑制界面反应的进行.     

大厚度TiAlN涂层力学性能的研究

采用电弧离子镀技术在不锈钢基体上制备了大厚度TiAlN涂层,并对大厚度涂层的力学性能进行了系统的研究。结果表明:梯度增加和循环增加N2流量制备大厚度涂层的厚度分别达到68.79μm和64.48μm,且涂层力学性能良好;大厚度涂层残余应力沿层深的分布,总体趋势从膜基界面向表面逐渐增大,全膜厚平均压应力低于1GPa,表面硬度近2000HV,循环大厚度涂层的膜基结合好于梯度大厚度涂层,而梯度大厚度涂层展现出更低的摩擦系数与磨损率。     

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.     

Cf/ZrC-ZrB2-SiC-C超高温陶瓷复合材料的显微结构表征

利用X-射线衍射、扫描电子显微镜和透射电子显微镜对Cf/ZrC-ZrB2-SiC-C超高温陶瓷复合材料的相组成、纤维/热解碳层的界面特征和超高温陶瓷基体的显微结构特征进行了表征。在碳纤维表面有一层厚度为2～3μm石墨化程度较高的热解碳界面层,该界面层可以避免采用PIP工艺制备超高温陶瓷基体时可能对碳纤维造成的损伤。热解碳层与碳纤维之间为弱机械结合,其界面间分布着20～30 nm的ZrC纳米颗粒。Cf/ZrC-ZrB2-SiC-C超高温陶瓷复合材料基体主要由ZrC,ZrB2,SiC和石墨相(Cg)组成。基体中石墨的(002)面沿着ZrC,ZrB2或SiC的表面生长。在石墨与ZrB2和石墨与SiC的界面没有观察到取向关系,界面处既没有反应层也没有非晶相存在。在石墨与ZrC之间存在ZrC(111)∥Cg(002),ZrC[110]∥Cg[010]的取向关系。ZrB2和SiC之间也没有界面反应和非晶层存在。     

化学镀镍对碳纤维增强聚酰亚胺表面WC/Co涂层抗热震性能的影响

在航空发动机涡轮叶片用碳纤维增强聚酰亚胺(C/PMR15)复合材料表面喷涂WC/Co涂层可以提高其抗氧化耐冲刷性能,采用整体热震法能够评定涂层与基体的结合力.研究了在C/PMR15基体上化学镀镍作为粘结底层对WC/Co喷涂层抗热震性能的影响,并与喷涂PMR15粉末作为过渡层的方法进行了比较.结果表明,在PMR15过渡层上不能得到完整的后续涂层,在化学镀镍粘结底层上可得到连续致密的镍基合金层和WC/Co涂层,镀镍层大幅度提高了基体抗氧化能力,缓和了WC/Co涂层和基体界面位置的热应力,涂层抗热震性提高.     

C涂层对SiC纤维增强Ti基复合材料界面行为的影响

采用透射电镜和扫描电镜研究了SiC纤维增强Ti基复合材料的界面反应,重点分析了C涂层对界面行为的影响。结果表明,C涂层可以明显改善纤维和基体之间的界面结合状况;SiC／C／Ti-6A1-4V复合材料的界面反应产物是主要为TiC,而无C涂层SiC／Ti-6A1—4V的界面反应产物为TiC,Ti5Si3和Ti3SiC2界面反应层生长受扩散控制,其厚度增长满足抛物线生长规律,SiC／C／Ti-6A1—4V由于C涂层消耗完毕前后的不同情况,其界面反应层生长并不完全符合这一规律,C涂层的存在可以有效的抑制界面反应的进行。     

界面过渡层对SiC/Al双连续相复合材料性能的影响

研究了界面过渡层对SiC/Al双连续相复合材料性能的影响.结果表明,界面过渡层降低了复合材料中的残余应力,改善了界面的结合,提高了复合材料的压缩性能.当界面过渡层中SiC的体积分数接近50%时,复合材料的压缩强度最高,塑性最好,但弹性模量较低.界面过渡层的存在改变了复合材料的弯曲断裂机制.SiC原始泡沫增强的复合材料在断裂时,增强体SiC泡沫先断裂,基体后破坏,断裂表面凹凸不平;含界面过渡层的复合材料断裂时,过渡层的外侧界面先被撕开,内侧界面结合良好,基体与增强体同时断裂,断口平整.     

Interfacial structure, residual stress and adhesion of diamond coatings deposited on titanium

The interfacial structures of diamond coatings deposited on pure titanium substrate were analyzed using scanning electron microscopy and grazing incidence X-ray diffraction. Results showed that beneath the diamond coating, there was one titanium carbide and hydride interlayer, followed by a heat-affected and carbon/hydrogen diffused Ti layer. Residual stress in the diamond coating and TiC interlayer under different process parameters were measured using Raman and X-ray diffraction (XRD) methods. Diamond coatings showed large compressive stress on the order of a few giga Pascal. XRD analysis also showed the presence of compressive stress in the TiC interlayer and tensile stress in the Ti substrate. With increasing deposition duration, or decreasing plasma power and concentration of CH₄ in gas mixture, the compressive residual stress in the diamond coating decreased. The large residual stress in the diamond coating resulted in poor adhesion of the coatings to substrate, but adhesion was also related to other factors, such as the thickness and nature of the TiC interlayer, etc. A graded interlayer design was proposed to lower the thermal stress, modify the interfacial structure and improve the adhesion strength.     

Hardness and indentation-induced damage of SiC-coated graphite

The hardness and indentation damage of chemical vapour-deposited SiC coating/graphite substrate composites have been studied. Experimental results indicate that hardness is a non-linear function of coating thickness, and is not significantly affected by the changes in the magnitude of the residual stresses in SiC coating. The size of indentation lateral crack, observed using optical microscopy, varies with coating thickness. Acoustic emission spectra show that thinner coatings suffer more extensive fracture as compared with thicker coatings.     

Crack propagation modeling on the interfaces of thermal barrier coating system with different thickness of the oxide layer and different interface morphologies

A finite element model (FEM) is developed to simulate the crack development in a typical plasma sprayed thermal barrier coatings system in consequence of the stresses induced by thermal cycling, the growth of the oxide layer and different interface morphologies. The thermo-mechanical model is designed to takes into account a non-homogenous temperature distribution and the effects of the residual stress generated during coating process.     

X射线测量高速钢上不同厚度氮化钛涂层残余应力

采用多弧离子镀在AISIM2高速钢(HSS)上沉积了TiN硬涂层,试样中基体厚度为1mm,涂层厚度分别为3.0、5.0、7.0、9.0和11.0μm.应用X射线衍射(XRD)分析了TiN涂层中残余应力,测量了TiN(220)衍射晶面在五种不同倾斜角(Ψ=0°,20.7°,30°,37.8°和45°)下的X射线衍射峰.结果表明:在3～11μm涂层厚度范围内,TiN涂层中均表现出残余压应力且残余压应力值较大.TiN涂层中残余应力大致分布在-3.22～-2.04GPa之间,本征应力分布在-1.32～-0.14GPa,热应力约为-1.86～-1.75GPa.TiN涂层中残余应力值随涂层厚度变化是非线性增加的,随厚度增加表现出先增大后减小的变化趋势,多项式拟合后发现约在8.5μm厚时残余应力达到最大值.     

CVD-SiC界面改性涂层对气相渗硅制备C_f/SiC复合材料力学性能的影响

在气相渗硅制备C_f/SiC复合材料时,界面改性涂层非常重要。良好的界面改性涂层一方面起到保护碳纤维不受Si反应侵蚀的作用,另一方面起到调节纤维和基体界面结合状况。通过在C纤维表面制备CVD-SiC涂层来进行界面改性,研究CVD-SiC界面改性涂层对GSI C_f/SiC复合材料力学性能和断裂特征的影响,并分析其影响机制。结果表明:无CVD-SiC涂层改性的C_f/SiC复合材料力学性能较差,呈现脆性断裂特征,其强度、模量和断裂韧度分别为87.6MPa,56.9GPa,2.1MPa·m1/2。随着CVD-SiC涂层厚度的增加,C_f/SiC复合材料的弯曲强度、模量和断裂韧度呈现先升高后降低的趋势,CVD-SiC涂层厚度为1.1μm的C_f/SiC复合材料的力学性能最好,其弯曲强度、模量和断裂韧度分别为231.7MPa,87.3GPa,7.3MPa·m1/2。厚度适中的CVD-SiC界面改性涂层的作用机理主要体现在载荷传递、"阻挡"Si的侵蚀、"调节"界面结合状态3个方面。     

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).     

Analysis of Interfacial Coating Effect on Thermal Stress in Composites

A preliminary model for the analysis of thermo-mechanical behaviour of interfacial coatings on thefibers in unidirectional composites have been developed on the solution of thermo-elastic mechan-ics. Thermal stress would be introduced into the composite during cooling because of the mismatchof thermo-mechanical properties among their components. The low modulus coating can effectivelyreduce the interracial stress caused by different thermal expansion coefficient between fibers and ma-trix, no matter how high or low the expansion coefficients of coatings are in CF/Al and SiC/Ticomposite systems, however, high modulus coating can decrease the interfacial compressive stress,only when the thermal expansion coefficient of coating is lower.     

化学镀Ni-P-SiC镀层的微观组织结构特征

对化学镀Ni-P-SiC复合镀层的微观组织结构特征进行了研究，结果表明，SiC微粒弥散分布在复合镀层中，Ni-P合金主要作为粘结金属包络着SiC微粒，两之间存在电子转移，发生了界面反应，反应扩散层为10^-1nm级，界面结合紧密，无孔隙和裂纹等缺陷。元素存在形态主要表现为Ni和P以单质的形式存在，Si以共价健SiC的形式存在，Ni－Ni之间以金属键进行结合。