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中文摘要：
采用有限元软件中的间接热力耦合方法,建立等离子喷涂纳米团聚体ZrO2-7%Y2O3（质量分数）粉末热力耦合有限元模型,对喷涂过程中粉末的热应力进行研究,分析粉末直径和喷嘴出口处等离子焰流温度对粉末应力的影响。同时进行相应的等离子喷涂试验,并从理论上分析喷涂过程中粉末破碎的原因及破碎机理。结果表明：在等离子喷涂过程中,粉末中心存在较大的拉压力,随着粉末飞行时间的增加,粉末中心拉应力先增加后减小;粉末直径越大,粉末中心最大拉应力越大,出现最大拉应力的时间越晚;喷嘴出口处等离子体温度越高,粉末中心的最大拉应力也越大,而出现最大拉应力的时间没有明显差别;等离子喷涂纳米涂层的表面有3类组织,单个或少量纳米粒子团、以亚微米级尺度为主的小球以及较大尺度的不规则体;这3类组织是由等离子喷涂过程中纳米团聚体粉末内部较大的拉应力而引起粉末破碎形成的,其破碎形式与爆炸破碎机理相符。
英文摘要：
A finite element model for analyzing the stress field of nanostructured agglomerated ZrO2-7%Y2O3（mass fraction） powders during plasma spraying process was established by an indirect thermal-mechanical coupling method.And the influence of powders diameter and temperature of jet nozzle exit on feedstock＇s stress was studied.Meanwhile,the plasma spraying experiment of using nanostructured agglomerated powders was carried out,and the disintegration mechanism of powder was discussed according to the results of the stress filed and experiment.The results show that the maximal tensile stress locates at the powder center,and the tensile stress of powder center increases at first and then reduces with increasing flying time during the plasma spraying process.With the increase of the powder diameter,the maximal tensile stress increases,while the maximal tensile stress comes late.With the increase of the temperature of jet nozzle exit,the maximal tensile stress also increases,and the temperature of jet nozzle exit has no obviously effect on the time of reaching the maximal tensile stress.The surface morphology of the plasma-sprayed nanostructured coating exhibits some pieces of feedstock,which is composed of single or a few agglomerated nanoparticles,submicron spheres and irregular pieces.The formation of these pieces is attributed to the disintegration of feedstock due to the high tensile stress of the powder center.The disintegration mechanism of nanostructured agglomerated powders is an explosive disintegration.
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