共查询到19条相似文献,搜索用时 156 毫秒
1.
AT40陶瓷涂层与黏结层界面裂纹萌生、扩展是导致涂层失效的主要原因,制备多层陶瓷/金属低应力涂层为陶瓷涂层增韧的方法之一。利用APS(大气等离子喷涂)在Q235上制备AT40-NiAl-AT40-NiAl四层复合多层涂层并对复合多层进行热处理。使用SEM、EPMA、3PB等表征手段研究热处理对四层复合金属-陶瓷涂层的微观结构及涂层断裂韧性的影响。结果表明,热处理过程中陶瓷层-黏结层界面、陶瓷层富Al相富Ti相界面均发生了元素扩散;热处理后陶瓷层硬度增加30%,复合涂层断裂韧性提高。热处理过程中元素扩散形成的氧化物一方面在黏结层与陶瓷层之间形成钉扎效应增强黏结性,另一方面填充涂层中的孔隙、裂纹等缺陷提高涂层的硬度,降低裂纹扩展的面积从而提升涂层的断裂韧性。多层金属陶瓷沉积形成的复合陶瓷涂层及对其使用热处理的方法能有效提升AT40等陶瓷涂层的断裂韧性,对解决铁基零部件表面耐磨陶瓷容易脆断失效和扩展陶瓷涂层的应用范围提供了新的思路。 相似文献
2.
采用纳米压入方法表征了热浸镀铝钢表面由Al2O3层、Al层和FeAl层组成的复合涂层的纳米硬度、弹性模量及断裂韧性等微观力学性能,采用扫描电镜(SEM)观察了纳米压痕形貌,并分析了孔洞对陶瓷层的纳米压入行为和压痕裂纹扩展的影响.结果表明:等离子体电解氧化(PEO)陶瓷层中包含许多微米和亚微米尺度的细小孔洞,陶瓷层弹性模量约为226.4 Gpa,纳米硬度约为19.6 Gpa.当纳米压入深度为250 nm时,所测得陶瓷层的力学参数分散性较大.与FeAl层比较,PEO陶瓷层具有较高的裂纹扩展阻力. FeAl层纳米压痕顶端产生了沿直线扩展的径向裂纹;而陶瓷层纳米压痕中除径向裂纹外出现了侧边裂纹. 相似文献
3.
李维红 《稀有金属材料与工程》2009,38(Z2)
脆性材料的破坏通常是瞬态快速断裂,亚临界慢裂纹扩展特别是宏观慢扩展,很难在实验中观察.它一定程度上制约了玻璃陶瓷等材料的失效过程分析和阻力特性研究.本研究利用MFPA2D(Material Failure Process Analysis)软件成功地模拟了玻璃类脆性材料在平面应力状态下承受单向、双向应力时的亚临界裂纹扩展全过程,着重研究了脆性材料的慢裂纹扩展和扩展速度所受双向应力的影响,并讨论这种影响的机理和作用.通过声发射特性的数值模拟得到脆性材料在单向及双向应力状态下的亚临界裂纹扩展长度-荷载步曲线.结果表明,平行于裂纹面的拉应力对裂纹扩展有一定程度的阻碍作用,而平行于裂纹的压应力对裂纹有驱动效果.该数值实验结果与相关的实验结果取得了较好的一致,表明数值实验的可靠性,从而为脆性材料的可靠性和寿命评价提供理论基础和手段. 相似文献
4.
EB-PVD热障涂层的弹性模量和断裂韧性研究 总被引:3,自引:0,他引:3
用压痕法测量EB-PVD热障涂层的弹性模量及断裂韧性。发现热障涂层的Vickers显微硬度和弹性模量随施压载荷增大而减小,当载荷为2.94N时,显微硬度和弹性模量接近稳态值,分别为6.3GPa和172GPa;断裂韧性平均值约为1.81MPa·m1/2。压痕法测得陶瓷层断裂韧性数据波动较大,其主要原因是陶瓷层显微结构不均匀,使压痕裂纹在涂层不同局部区域所遇到的扩展阻力不同。 相似文献
5.
采用梯度热循环试验和有限元分析相结合的方式定量表征了等离子喷涂热障涂层陶瓷层内部裂纹尺寸与涂层表面亮斑尺寸的关系. 单次热循环试验包括120 s加热和120 s冷却. 采用三维模型分析陶瓷层内部裂纹对涂层传热过程的影响. 结果表明,随着陶瓷层内部裂纹扩展其表面温度升高,影响区域增大,持续升高的温度为裂纹上方陶瓷层加速烧结提供了必要条件;陶瓷层表面亮斑形状是其内部裂纹形状的直观反映;亮斑尺寸与裂纹尺寸的关系与裂纹扩展位置无关,二者的尺寸基本相同,因此可将亮斑尺寸视作裂纹尺寸. 相似文献
6.
YSZ热障涂层材料抗热震性能研究 总被引:1,自引:0,他引:1
以目前常用的高温热机热障涂层材料YSZ的热震实验为基础,重点讨论了热震温差与裂纹扩展的关系,以此确定材料的临界温差ΔTc的值,并分析热震过程对样品部分力学性能的影响。结果表明,大气等离子喷途(APS)法制备的YSZ涂层的临界温差ΔTc在425℃左右。涂层在热震过程中的裂纹扩展基本符合Hasselman模型。在表面热应力的影响下,热震后样品的硬度及断裂韧性均随ΔT升高而呈下降趋势。 相似文献
7.
8.
SiC/C层状陶瓷的断裂行为研究 总被引:4,自引:0,他引:4
利用流延法成膜和热压烧结工艺制备出了SiC层和石墨层交替排列、层厚均匀、界面清晰的SiC/C层状陶瓷。力学性能与单相SiC陶瓷相比,SiC/C层状陶瓷的抗弯强度略有降低,但断裂韧性却得到了大幅度的提高。层状陶瓷的载荷-位移曲线不同于单相陶瓷的1次性断裂曲线,而是呈锯齿状;同理论计算所得载荷-位移曲线相似。层状陶瓷的断裂路径呈台阶状,裂纹遇到弱界面时发生分叉产生并行扩展裂纹、晶须状微裂纹以及裂纹遇到弱界面时被吸收。认为裂纹偏转、裂纹分叉、裂纹并行扩展、裂纹遇弱界面被吸收等是SiC/C层状陶瓷的几种主要增韧机制。 相似文献
9.
采用流延/层的方法制备了B4C/BN层状陶瓷复合材料,研究了材料结构、B4C/BN层厚比、基体厚度对陶瓷材料强度和断裂韧性的影响.采用三点弯曲法和压痕强度法分别测试了材料的弯曲强度和断裂韧性.采用SEM分析手段对层状陶瓷的显微结构和裂纹偏转进行了研究.结果表明,当B4C/BN陶瓷层厚比在15左右时,层状陶瓷的弯曲强度达到448 MPa,断裂韧性达到7.86 MPa.m1/2.BN的弱界面对裂纹的偏转、分层和残余应力增韧是使得陶瓷材料断裂韧性提高的主要原因. 相似文献
10.
本文研究了蠕变断裂韧性对二种低合金耐热钢蠕变裂纹开裂和扩展的影响。试验表明:随着蠕变断裂韧性提高,抗蠕变裂纹开裂和扩展能力增加。材料呈韧性或脆性状态时,蠕变裂纹萌生和扩展过程不同。韧性状态时,裂纹为穿晶和晶界二种混合形式:穿晶裂纹可在晶内碳化物处发生,或在晶界上形核后向晶内扩展,晶界裂纹仍是由晶界上空洞形成和相互连接而成,裂纹可沿晶界和晶内扩展,但不连续。脆性状态时,裂纹沿晶界发生,它是由晶界形成空洞和相互连接而成,扩展仅沿晶界发生。 相似文献
11.
硬质陶瓷涂层增韧及其评估研究进展 总被引:2,自引:2,他引:0
硬质陶瓷涂层一般硬度高,但韧性差,在受到较大外加冲击荷载作用时容易产生裂纹并引发失效,从而限制了硬质涂层在工程领域的应用。硬质涂层的增韧研究是当前硬质涂层研究的热点之一。常见硬质涂层增韧方法中,有些是以降低硬度为代价来提高涂层韧性,比如第二相增韧;有些是通过优化涂层结构设计,减小缺陷尺寸,在不损失涂层高硬度的前提下,提高韧性,获得兼具高硬度和高韧性的涂层;有些是通过相变(晶体结构转变)提高涂层的韧性。通过优化涂层结构设计,改变涂层晶粒尺寸、晶界尺寸与复杂程度等,使涂层致密化,从而提高涂层硬度与韧性,从而获得增韧效果,成为研究者越来越关注的焦点。单一增韧方法的局限性,可以通过多种增韧方法协同作用获得突破,协同增韧已成为硬质涂层增韧发展的趋势。目前硬质涂层的韧性评估还没有一个公认的方法,从简单实用出发,常用的有微悬臂梁弯曲法、划痕法和压痕法。 相似文献
12.
低碳钢冷脆特征温度的研究SCIEI 总被引:1,自引:0,他引:1
本文根据低碳钢裂缝弯曲试样的冷脆行为特征,定义了冷脆特征温度T_(4m),并阐明了相应的物理含义。同时,对在这一温度下发生的断裂韧性及止裂特性转折的力学本质进行了阐述。在上述研究基础上,对T_(pm)温度在低碳钢冷脆评定中的应用价值进行了探讨。 相似文献
13.
The fracture toughness of plasma-sprayed Al2O3 coatings in terms of critical strain energy release rate G
Ic was investigated using a tapered double cantilever beam (TDCB) approach. This approach makes the fracture toughness be measured
only using the critical fracture load disregarding crack length during test. The Al2O3 coatings were deposited under different spray distances and plasma powers to clarify the effect of spray parameters on the
G
Ic of the coatings. The fracture surfaces were examined using scanning electron microscope. On the basis of an idealized layer
microstructure model for thermal sprayed coatings, the theoretical relationship between the cohesive fracture toughness and
microstructure is proposed. The correlation between the calculated fracture toughness and observed value is examined. It was
found that the fracture toughness of plasma sprayed Al2O3 coatings is not significantly influenced by spray distance up to 110 mm, and further increase in spray distance to 130 mm
resulted in large decrease in the fracture toughness of the coatings. The G
Ic value predicted based on the proposed model using lamellar interface mean bonding ratio and the effective surface energy
of bulk ceramics agreed well with the observed G
Ic data. Such agreement evidently shows that the fracture toughness of thermally sprayed ceramic coatings at the direction along
coating surface is determined by lamellar interface bonding. 相似文献
14.
HUANG Zheng Institute of Physics Academia Sinica Beijing ChinaYAO Mei Harbin Institute of Technology Harbin China Institute of Physics Academia Sinica Beijing China 《金属学报(英文版)》1990,3(5):332-337
On the basis of analysis of low carbon steel fracture macro-features and micro-processes atlow temperature,the definition was given of the characteristic transition temperature ofbrittleness,T_(pm),and its physical meaning was expounded.Discussion was carried out of phys-ical characteristic of variation at T_(pm) in respect of the fracture toughness and property ofcrack arrest.In addition,research was made on the application of T_(pm),which can give infor-mation about the transition of the fracture toughness,the property of crack arrest and criticalcrack size,to estimation the brittleness of low carbon steel at low temperatures. 相似文献
15.
Al2O3基陶瓷材料是现代陶瓷材料学的一个重要组成部分,与其它材料相比,Al2O3具有许多独特、优良的性能,特别是其表现出较好的摩擦学性能。然而,其韧性低、脆性大的弱点在一定程度上限制了它在摩擦学领域的应用。为了减小Al2O3基陶瓷材料的脆性,除了采用先进的制备工艺外,各国学者相继研究开发了多种Al2O3陶瓷材料的增韧补强方法,显著改善了陶瓷材料的脆性并使其耐磨性显著提高。基于增强相的种类和增强手段,本文综述了Al2O3基陶瓷材料摩擦学的发展现状,并提出Al2O3基复相陶瓷今后有待研究的课题和发展方向。 相似文献
16.
不同工艺烧结钕铁硼磁体的脆性分析 总被引:1,自引:0,他引:1
不同工艺生产的烧结钕铁硼磁体的脆性(冲击韧性)差异很大。其中,传统工艺磁体的冲击韧性最好,合金锭加氢化工艺磁体稍差,而速凝(SC)加氢化磁体的冲击韧性值仅约为前两者的1/2。扫描电镜断口观测显示不同磁体微观断裂机制不同。传统工艺磁体的裂纹源于主相晶粒内部的解理断裂;合金锭加氢化磁体的裂纹可能起源于主相边界上附着的富钕相颗粒;而SC加氢化磁体的裂纹源于主相的穿晶断裂。XRD分析表明两种氢化磁体脆性差异是因为各自在氢化破碎过程中参与氢化的相不同。合金锭加氢化磁体只有富钕相参与氢化;而SC加氢化磁体主相晶粒参与了氢化。 相似文献
17.
Interface fracture toughness and fracture mechanisms of thermal barrier coatings investigated by indentation test and acoustic emission technique
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Interface fracture toughness and fracture mechanisms of plasma-/sprayed thermal barrier coatings (TBCs) were investigated by interfacial indentation test (IIT) in combination with acoustic emission (AE) measurement. Critical load and AE energy were employed to calculate interface fracture toughness. The critical point at which crack appears at the interface was determined by the IIT. AE signals produced during total indentation test not only are used to investigate the interface cracking behavior by Fast Fourier Transform (FFT) and wavelet transforms but also supply the mechanical information. The result shows that the AE signals associated with coating plastic deformation during indentation are of a more continuous type with a lower characteristic frequency content (30-60 kHz), whereas the instantaneous relaxation associated with interface crack initiation produces burst type AE signals with a characteristic frequency in the range 70-200 kHz. The AE signals energy is concentrated on different scales for the coating plastic deformation, interface crack initiation and interface crack propagation. Interface fracture toughness calculated by AE energy was 1.19 MPam1/2 close to 1.58 MPam1/2 calculated by critical load. It indicates that the acoustic emission energy is suitable to reflect the interface fracture toughness. 相似文献
18.
For the thermal spray industry to progress, informative and reliable coating evaluation techniques are needed. Measurement
of adhesion is an important function, and existing tests have severe limitations. The peel adhesion test (PAT) was adapted
to thermal spray coatings (TSC) from the adhesives industry. In this test, a thin metal foil is coated by thermal spraying.
The foil is then peeled off the coating at a constant speed. The force required for separation is monitored as a function
of crack position. The force is than converted into a peel strength that is equivalent to the energy required for separation.
The adhesion of a range of different TSCs was measured in the form of spray pattern profiles and uniform coatings. Results
were compared with the ASTM standard for TSC adhesion measurement, the expected range of interface toughness, and the Vickers
hardness of the coating. Comparisons indicate that the PAT is self consistent, and it produces results comparable to other
toughness measurements. The peel test was used to determine interface toughness in the range of 10 to 60 J/m2 for ceramic coatings, 150 to 250 J/m2 for cermet coatings, and 160 to 300 J/m2 for metal coatings. 相似文献
19.
为解决 YSZ(Y2O3 部分稳定的 ZrO2 ) 陶瓷基高温封严涂层沉积效率较低和易于过早剥落失效的问题,选择氧化铝 (Al 2O3 )、钇铝石榴石(Y3Al 5O12 ,YAG)及镁铝尖晶石(MgAl 2O4 )为三种高温黏结相,通过喷雾造粒的方法分别制备出 B0(无黏结相)、B1(含 Al 2O3 )、B2(含 YAG)和 B3(含 MgAl 2O4 )等四种 YSZ 基团聚颗粒,研究黏结相对涂层沉积效率和热循环性能的影响。 结果表明,YAG 的黏附和包裹作用最强,与 B0 型粉末相比,B2 型粉末的沉积效率提高了 181. 49%;热循环过程中不断增长的裂纹扩展驱动力和陶瓷材料的脆性属性是导致陶瓷涂层剥落失效的主要原因,由于 YAG 相的弥散增韧作用,B2 型涂层的断口呈现出类韧窝形貌,与 B0 型涂层相比,B2 型涂层的断裂韧性提高了 39. 76%,热循环寿命提高了 43. 68%。 YAG 黏结相的添加显著地提高了 YSZ 陶瓷基高温封严涂层的沉积效率,同时较好地提高了涂层的热循环寿命。 相似文献