Influence of Additive Silica on the Laser Melting of the Ceramic Coatings

• 作 者: Yuanzheng YANG Xiaojun BAI Zhi
• 机 构: Faculty of Material and Energy,Dept. of Mechano-Electronic Engineering,Institute of Metal Research
• 出 处: 材料科学技术学报
• 发表日期: 2004年期
• 关键词: Plasma spraying Laser remelting Additive silica Stress crack
• 基金项目: This work was supported by Doctoral Foundation of Ministryof Education of China;广东省自然科学基金

The influence of additive silica on the microstructure of plasma sprayed Al2O3 and Al2O3+13 wt pct TiO2 ceramiccoatings at laser melting has been investigated in this study. At the laser melting, additive silica in Al2O3 ceramiccoating can reduce the stress of cooling shrinkage generated during solidification. Moreover, silica can render finersize of grains of the melting layer and form continuous glassy matter around the grain boundaries so as to reducefurther the cooling stresses and to suppress the formation and spreading of cracks. On the other hand, at the lasermelting, TiO2 reacts with Al2O3 and transforms into TiAl2Os. The latter new phase has great and anisotropiccoefficients of thermal expansion leading to big and asymmetrical stresses and thus to form cracks in the meltinglayer of Al2O3+13 wt pct TiO2 coating. Due to the fact that the influence of additive silica on the suppression of theformation of cracks is rather limited and cannot counterbalance the negative effect of TiAl2O5, thus the melting layerof Al2O3+13 wt pct TiO2 coating doped with 3 wt pct SiO2 cracks also. Nevertheless, TiO2 can greatly developthe wear resistance of the ceramic coating as sprayed or laser melted.