(1. 銅陵學(xué)院 機(jī)械工程系，銅陵 244000；2. 南京航空航天大學(xué) 機(jī)電學(xué)院，南京 210016)
摘 要: 采用有限元軟件中的間接熱力耦合方法，建立等離子噴涂納米團(tuán)聚體ZrO2-7%Y2O3(質(zhì)量分?jǐn)?shù))粉末熱力耦合有限元模型，對(duì)噴涂過程中粉末的熱應(yīng)力進(jìn)行研究，分析粉末直徑和噴嘴出口處等離子焰流溫度對(duì)粉末應(yīng)力的影響。同時(shí)進(jìn)行相應(yīng)的等離子噴涂試驗(yàn)，并從理論上分析噴涂過程中粉末破碎的原因及破碎機(jī)理。結(jié)果表明：在等離子噴涂過程中，粉末中心存在較大的拉壓力，隨著粉末飛行時(shí)間的增加，粉末中心拉應(yīng)力先增加后減小；粉末直徑越大，粉末中心最大拉應(yīng)力越大，出現(xiàn)最大拉應(yīng)力的時(shí)間越晚；噴嘴出口處等離子體溫度越高，粉末中心的最大拉應(yīng)力也越大，而出現(xiàn)最大拉應(yīng)力的時(shí)間沒有明顯差別；等離子噴涂納米涂層的表面有3類組織，單個(gè)或少量納米粒子團(tuán)、以亞微米級(jí)尺度為主的小球以及較大尺度的不規(guī)則體；這3類組織是由等離子噴涂過程中納米團(tuán)聚體粉末內(nèi)部較大的拉應(yīng)力而引起粉末破碎形成的，其破碎形式與爆炸破碎機(jī)理相符。
關(guān)鍵字: 納米團(tuán)聚體粉末；等離子噴涂；數(shù)值模擬；溫度場；應(yīng)力場；破碎機(jī)理
nanostructured agglomerated powder during plasma spraying process
（1. Department of Mechanical Engineering, Tongling College, Tongling 244000, China;
2. College of Mechanical and Electrical Engineering,
Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China）
Abstract: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.
Key words: nanostructured agglomerated powders; plasma spraying; numerical simulation; temperature field; stress field; disintegration mechanism
