层状相分布及金属陶瓷过渡区对涂层力学性能的影响

发布时间：2018-03-04 21:30

本文选题：涂层　切入点：力学性能　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：Al2O3-40wt%TiO2涂层(AT40涂层)广泛的应用于机械、纺织、冶金等工业领域。等离子喷涂沉积Al2O3-40wt%TiO2涂层具有高硬度、高耐磨性、摩擦系数低、化学性能稳定等特点。随着工业服役条件越来越苛刻,对涂层的性能提出了更高的要求。纳米材料有强的比表面活性和小尺度效应,纳米结构Al2O3-40wt%TiO2涂层具有更加优异的性能,但是制备纳米结构涂层工艺更复杂,工艺参数更加难控制。另外,梯度Al2O3-40wt%TiO2涂层和多层Al2O3-40wt%TiO2涂层能够减小涂层中的应力梯度,延长涂层的寿命。由于梯度涂层和多层涂层是经过多次喷涂制备而成,因此梯度和多层涂层中有更多的层间界面。在制备过程和服役过程中,缺陷很容易在层间界面上形成并扩展,最后导致涂层失效。通过掺杂也能改善涂层的性能,本文研究了 Y2O3掺杂对Al2O3-40wt%TiO2涂层性能的影响。通过双路送粉单次喷涂制备含有金属陶瓷过渡区的Al2O3-40wt%TiO2涂层(MAT40涂层),金属陶瓷过渡区代替AT40涂层中粘结层与陶瓷层的界面。本论文讨论了金属陶瓷过渡区对涂层性能以及失效机制的影响。获得的主要研究结论有如下几点:(1)采用等离子喷涂双路送粉单次喷涂方法制备了含金属陶瓷过渡区的Al2O3-40wt%TiO2涂层(MAT40)。比较AT40涂层和MAT40涂层的力学性能及失效机制发现,在热震试验和弯曲试验时MAT40涂层系统中应力梯度变小。形成的金属陶瓷过渡区替代了原本AT40涂层中陶瓷层与粘结层的界面,使得在MAT40涂层体系中除去粘结层与基体之间的界面外没有其它连续的界面。金属陶瓷过渡区的出现提高了涂层的抗热震性能和力学性能。通过分析试验过程中涂层的失效机制发现,金属陶瓷过渡区通过降低涂层内的应力梯度、偏转涂层中的裂纹扩展方向、塑性变形提高涂层的断裂韧性。(2)Al2O3-40wt%TiO2涂层中的层状相分布主要受预先沉积的表面形貌以及喷涂参数的影响。R/h≤al是形成非致密层状相分布的必要条件;预先沉积形貌的倾斜角(θ)决定非层状相分布的位置。(3)在维氏硬度测试过程中,应力释放机制主要受界面缺陷影响。当涂层中有很多的界面缺陷(微观裂纹、孔隙等)时,在维氏硬度计压头的作用下,裂纹很容易进一步沿着相与相之间的界面扩展。另外,在菱形压痕的尖角处也是应力集中的地方,容易产生裂纹。随着越来越多的裂纹与涂层中的孔隙连接导致涂层崩塌。涂层的崩塌使得硬度测量值变小。对于界面缺陷少的涂层,通过裂纹在菱形压痕的尖端形成并扩展来释放涂层中的应力。当裂纹的始端与末端相连接时,则会导致涂层的小块崩落并释放涂层中的应力。(4)热震试验和弯曲试验时,涂层内的裂纹在陶瓷区内是沿着柱状晶的晶间界面扩展。由于裂纹沿着多边形柱状晶的晶间界面扩展,在热震试验失效的表面能够发现规则的折线状形貌。在三点弯曲试验时,裂纹在陶瓷区域内同样是沿着柱状晶晶间界面生长,在断裂截面上能够明显看到柱状晶的晶界。NiAl合金区在弯曲试验中主要承受拉应力,在承受拉应力时发生拉伸塑性变形来释放应力直到断裂。(5)Y2O3的掺杂会降低AT40涂层的结构均匀性。8wt%Y2O3掺杂的Al2O3-40wt%TiO2涂层具有最高的耐磨性。耐磨性的提高主要是由于Y2O3的掺杂改善了 Al2TiO5的力学性能。(6)通过正交试验法分析得到沉积Al2O3-40wt%TiO2涂层的参数为:喷涂电流为500A、N2速率为2600mL/h、喷涂距离为110mm、送粉电压为8V。N2速率是对涂层硬度影响最大的参数,喷涂距离是对涂层磨损率影响最大的参数。获得的 Al2O3-40wt%TiO2涂层的最高硬度达到 1126HV0.2,Al2O3-40wt%TiO2涂层的最低磨损率为0.0387 mg/N.m。
[Abstract]:Al2O3-40wt%TiO2 coating (AT40 coating) is widely used in machinery, textile, metallurgy and other industrial fields. With high hardness of Al2O3-40wt%TiO2 coatings deposited by plasma spraying, high wear resistance, low friction coefficient, chemical stability and other characteristics. With the industrial service conditions have become increasingly demanding, put forward higher requirements on the performance of the coating nano materials have. Strong surface activity and small scale effect, nanostructured Al2O3-40wt%TiO2 coating has a more excellent performance, but the preparation of nanostructured coating process is more complex, more difficult to control the process parameters. In addition, the gradient Al2O3-40wt%TiO2 coating and multilayer Al2O3-40wt%TiO2 coatings can reduce the stress in the coating gradient, prolong the life of the coating. The coating and gradient the multilayer coating was prepared after spraying, so the gradient and multilayer coatings have more interface. Served in the preparation process and the In the process, defects easily in interface formation and expansion, resulting in failure of the coatings. The performance can also improve by doping coating, this paper studies the impact of Y2O3 doping on the properties of Al2O3-40wt%TiO2 coatings. Through dual single powder spraying Al2O3-40wt%TiO2 coating preparation containing ceramic metal transition zone (MAT40 coating). The metal ceramic transition zone instead of interfacial layer and ceramic layer in AT40 coatings. This paper discussed the influence of metal ceramic transition zone on the coating performance and failure mechanism. The main conclusions are as follows: (1) using a single powder spraying method Al2O3-40wt%TiO2 metal ceramic coating containing transition zone was obtained dual plasma spraying (MAT40). AT40 and MAT40 coatings, the mechanical properties and failure mechanisms are found in thermal shock test and bending test of MAT40 coating system in stress gradient formation. The metal ceramic interface transition zone replaced the ceramic layer and the bonding layer AT40 coating, the MAT40 coating system to remove the bond between the coating and the substrate interface interface. No other continuous metal ceramic transition region of the coating increased the thermal shock resistance and mechanical properties. Through the analysis of the failure mechanism of coating test in the process of discovery, metal ceramic transition zone by reducing the stress gradient coating, crack deflection in the coating growth direction, improve the plastic deformation of the fracture toughness of coatings. The influence of Al (2).R/h Al2O3-40wt%TiO2 lamellar phase in the coating distribution is mainly affected by the surface morphology of pre deposited and spraying parameters is a necessary condition for the formation of the non dense lamellar phase distribution; pre tilt angle (theta) morphology determines the non layered distribution position. (3) in the Vivtorinox hardness testing process, stress release mechanism is mainly affected by the world Effect of surface defect. When the coating has many interface defects (microcracks, pores), indenter hardness in Vivtorinox under the action of crack easily further along the interface between phases is extended. In addition, the diamond indentation at the angle of stress is concentrated, easy to crack with crack. With more and more pores in the coating coating. The coating of connection leads to collapse collapse makes the hardness measurement value becomes smaller. The coating interface less defects, extended to release the stress in the coating is formed by a crack in the diamond tip and indentation crack. When connected to the beginning and end to end, it will lead to small caving coating and relax the stress in the coating. (4) the thermal shock test and bending test, the crack in the ceramic coating area along the columnar crystal interface. The crack extended along the interface expanding polygon columnar crystal crystal In the exhibition, thermal shock test failure surface can be found in line shape rules. In the three point bending test, the crack in the ceramic region is the same along the columnar crystal growth interface, can the columnar grain boundary of.NiAl alloy in bending test mainly tensile stress was seen in the fracture section. In the tensile plastic deformation to release the stress until the fracture tensile stress. (5) the structure of the Y2O3 doped AT40 can reduce the coating uniform Al2O3-40wt%TiO2 coating doped with.8wt%Y2O3 has the highest wear resistance. The wear resistance is improved due to the doping of Y2O3 can improve the mechanical properties of Al2TiO5 (6) by. Orthogonal test analysis of parameters of Al2O3-40wt%TiO2 coating deposited by: spraying current of 500A, the N2 rate is 2600mL/h, the spraying distance is 110mm, the powder feeding rate is the maximum voltage of 8V.N2 parameters on the hardness of the coating, spraying Distance is the most influential parameter on the wear rate of the coating. The highest hardness of the obtained Al2O3-40wt%TiO2 coating reaches 1126HV0.2, and the lowest wear rate of the Al2O3-40wt%TiO2 coating is 0.0387 mg/N.m..

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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