等离子喷涂陶瓷颗粒的扁平化转变机制

Transition Mechanism in Flattening of Plasma Sprayed Ceramic Particles

我们之前对热喷涂金属粒子的扁平化转变行为进行了系统研究,并提出了形成机制假设:由于超快速冷却而优先在熔滴底部形成的冷却晶体结构决定着圆饼状熔滴的形成。为了验证这一机制是否适用其他材料,选取了几种具有不同热性能的陶瓷材料来进行对比。采用等离子喷涂技术分别将Al_2O_3、Y_2O_3和YSZ喷涂到AISI304不锈钢基体上,对圆饼状熔滴百分比随基体温度变化规律进行了研究,并对熔滴的横截面形貌也进行了观察。结果表明,在Al_2O_3和Y_2O_3熔滴底部均存在独特的非晶和冷晶结构,说明这些材料中圆饼状熔滴形成机制与金属中的相似。另一方面,在YSZ熔滴中却只有柱状晶结构,故圆饼状颗粒的形成机制假设只是适用于部分材料。

Transition in the flattening behavior of the thermally sprayed metallic materials has been recognizedin our previous systematic investigations.A hypothesis,ultra-rapid cooled chill structure preferentially formedat the bottom part of the splat,may play an essential role for the generation of the disk splat,has been proposed.Universality of this hypothesis beyond material difference was verified experimentally by using several kindsof ceramic materials,having different thermal properties.To perform this,Al2O3,Y2O3and YSZ particles wereplasma sprayed onto AISI304stainless steel substrate,and fraction of the disk splat with substrate temperatureincrease was investigated,followed by the precise observation on the cross-section microstructure of the splat.Theresults showed that unique amorphous and chill structure was observed in Al2O3and Y2O3splat at their bottompart,indicating that similar disk formation mechanism may act in these materials.On the other hand,only normalcolumnar structure was recognized in YSZ splat.As a result,the hypothesis was verified partially regardless of thematerials difference.