团聚粉末粒度对PS-PVD制备GYbZ热障涂层的性能影响

Effects of Agglomerated Powder Particle Size on Performance of GYbZ Thermal Barrier Coating Prepared by PS-PVD

目的探究不同粒度的微米级团聚粉末对等离子喷涂–物理气相沉(PS-PVD)制备GYbZ热障涂层性能的影响。方法以微米团聚的(Gd_(0.9)Yb_(0.1))_(2)Zr_(2)O_(7)(GYbZ)粉末为原料,通过PS-PVD工艺在镍基高温合金表面用3种不同粒径团聚粉末制备GYbZ热障涂层。采用扫描电子显微镜(SEM)和X射线衍射(XRD)分析GYbZ热障涂层的微观结构及相组成,采用电子万能试验机测试涂层的结合强度,采用自动水淬机对涂层的抗热震性能进行测试。结果随着团聚粉末粒度的减小,团聚粉末的球形度会变低,且粉末的孔隙率逐渐变大,团聚粉末粒度越小,喷涂的气化率越高,涂层中未熔粒子越少,涂层羽–柱状结构越明显。D50=13μm的团聚粉末在喷涂时,因粉末粒度过小,以及流动性较差,送粉过程中部分粉末未能顺利地通过喷嘴到达等离子焰流的中心,涂层的沉积率会略微降低。GYbZ团聚粉末衍射图呈现出Gd_(2)Zr_(2)O_(7)与Yb_(2)O_(3)这2种相的堆叠,而GYbZ涂层衍射图呈现单一的缺陷萤石结构。同时随着团聚粉末粒度的减小,制备出相应涂层的力学性能和抗热震性能有着明显的提高。结论采用D50=13μm的团聚粉末制备的涂层具有完整的羽毛–柱状结构,且拥有最高的结合强度及最好的抗热震性能。

The work aims to investigate the effects of different particle sizes of micron agglomerated powders on the properties of GYbZ thermal barrier coatings prepared by plasma spray-physical vapor deposition(PS-PVD).With micron agglomerated(Gd_(0.9)Yb_(0.1))_(2)Zr_(2)O_(7)(GYbZ)powder as raw material,the thermal barrier coating of GYbZ was prepared on the surface of nickel-based superalloy by PS-PVD process with three agglomerated powders with different particle sizes.The average particle size of the powder was 2-3μm.A planetary ball mill was used to mix the two powders.The molar ratio of Gd_(2)Zr_(2)O_(7)to Yb_(2)O_(3) was 9:1.The agglomerated powder obtained by spray granulation was sieved and dried in a constant temperature oven at 70℃ until taken out before spraying.In this paper,the preparation of the coating was divided into two stages:the preparation of the bonding layer and the preparation of the ceramic layer.Both the bonding layer and the ceramic layer were prepared by plasma spraying physical vapor deposition(PS-PVD).In this work,double-ceramic layer material system was adopted.In the GYbZ/YSZ double-ceramic layer thermal barrier coating system,the YSZ layer was located between the GYbZ and the metal bonding layer.YSZ can improve the thermal expansion coefficient mismatch between the GYbZ and the metal bonding layer.A YSZ layer with a thickness of about 200μm was prepared on the surface of the adhesive layer by PS-PVD technology,and then a GYbZ coating was prepared on the YSZ coating,and the thickness of the GYbZ coating was about 100μm.The total thickness of the ceramic layer was about 300μm.X-ray diffractometer(XRD)was used to analyze the phase of the sprayed agglomerated powder and sprayed coating;the surface and cross-section of the agglomerated powder and coating samples were observed by scanning electron microscope(SEM);The bonding strength of the coating was tested by the electronic testing machine;the thermal shock resistance of the coating was tested by an automatic water quenching machine.Results showed that with the decrease of the powder particle size,powders of spherical degree became worse,and the porosity of the powder increased gradually,The smaller the powder particle size,the higher the gasification rate of spraying,the less unmelted particles in the coating,and the more obvious the coating plume-columnar structure.However,when the powder with D50of 13μm was sprayed,due to the too small particle size and poor fluidity of the powder,part of the powder cannot pass through the nozzle smoothly and reach the center of the plasma flame during the powder feeding process.The deposition rate of the coating was slightly reduced.The GYbZ agglomerated powder diffraction pattern showed the stacking of Gd_(2)Zr_(2)O_(7) and Yb_(2)O_(3) phases,while the GYbZ coating diffraction pattern showed a single defect fluorite structure.At the same time,with the reduction of the particle size of the agglomerated powder,the mechanical properties and thermal shock resistance of the corresponding coatings were significantly improved.The conclusion of this paper is that the coating prepared with the agglomerated powder with D50 of 13μm has a complete feather-column structure with the highest bonding strength and the best thermal shock resistance.