附加屏蔽气体的大气等离子喷涂对热障涂层性能影响

Influence of gas shroud on property of plasma sprayed thermal barrier coating

对比研究了附加屏蔽气体的大气等离子喷涂和普通大气等离子喷涂对热障涂层组织结构和性能的影响.结果表明,附加屏蔽气体的大气等离子喷涂粘结层表面未熔或半熔粒子较少,涂层中氧化物夹杂和孔隙率降低,热障涂层在1 080℃下具有更好的抗氧化性能.附加屏蔽气体的大气等离子喷涂的热障涂层具有更好的抗氧化性能的原因,在于外加保护气氛减轻了喷涂过程中粒子和涂层的氧化,粘结层中Al元素含量更高,氧化初期粘结层表面优先形成致密的具有保护作用的Al2O3薄膜,使得界面热生长氧化物的生长速度减慢.

The comparative study were carried out on the microstructure as well as the properties of the coating prepared by atmospheric plasma spraying and shroud plasma spraying.The results showed that,compared to the conventional atmospheric plasma sprayed(APS)coating,the shroud plasma sprayed (SPS)coating contained less unmelted or partially melted particles and oxide content,and porosity was lower.The SPS coating presented superior oxidation resistance at 1 080℃than the APS one.The reason owed to the mitigation of the involvement of the surrounding air that caused turbulent of the plasma,consequently,the particles were more fully melted and less oxide formed in the coating.The finally deposited SPS coating was denser and contained more Al element,which induced the formation of compact Al2O3 layer at the early stage of oxidation.This compact Al2O3 layer would slow down the thickening rate of thermally grown oxide(TGO)that provides better resistance to the bond layer,therefore the SPS coating presents higher resistance to high temperature oxidation.