大气等离子喷涂用硼化锆粉体的喷雾造粒制备研究

Preparation ofzirconium diboride powder by spray granulation for atmospheric plasma spraying method

ZrB2基超高温陶瓷在航空航天、电子和核工业等许多方面有广泛的应用前景,一般工艺合成的硼化锆粉末粒径较小,难以直接用于大气等离子喷涂,需要二次造粒.本文研究了喷雾造粒法中固含量、粘结剂含量、进风温度和进料速率等参数和热处理工艺对制备ZrB2粉体粒径分布和形貌的影响.结果表明,浆料固体质量分数为40%~45%,粘结剂PVA质量分数为0.4%,进风温度为240~270℃,喷头转速为30r/s,蠕动泵进料速率为30~50r/min时,可制得粒径分布集中、球形度高的ZrB2造粒粉体.然后再对该粉体进行热处理,在500℃排胶1h,1100~1500℃烧结1h的条件下,烧结后的粉体保持了原有球形形貌,平均粒径收缩至70μm左右,具有良好的致密度,适合用于大气等离子喷涂.

Zirconium diboride(ZrB2)based ultra-high temperature ceramics have wide application prospects in aerospace,electronics and nuclear industries.Particle size of synthetic ZrB2 powders is excessively small and hard to be directly used in atmospheric plasma spraying(APS).Therefor the effects of spray-drying parameters such as solid content,binder content,inlet air temperature and feed rate and heat treatment process on the particle size distribution and morphology of the granulated zirconium diboride powder were studied to optimize the spray drying process and heat treatment method.As shown in the results,at the condition:mass fraction of slurry’s solid contents is 40%~45%,mass fraction of PVA binder is 0.4%,inlet air temperature is 240~270℃,nozzle speed is 30 r/s,and peristaltic pump feed rate is 30~50 r/min,the granulated ZrB2 powder have concentrated particle size distribution and high sphericity.The loose powder sintering method is used for heat treatment.Discharging binder at 500℃for 1h and sintering at 1100~1500℃for 1 h.After heat treatment,the ZrB2 powders maintain the original spherical morphology and have a favorable density,the average particle size shrinks to about 70μm,excellently fit the demands for atmospheric plasma spraying.