热障涂层在热腐蚀条件下的破坏过程

研究了K3合金上NiCrAlY-ZrO_2·8％Y_2O_3涂层在热腐蚀条件下的破坏行为。熔盐沿陶瓷层晶界向内渗透导致底层的腐蚀,以及Y_2O_3的酸性溶解导致ZrO_2由C相向M相的转变是热障涂层热腐蚀破坏的主要原因。某些工艺因素导致涂层破坏或不稳定会造成涂层过早地灾难性破坏。

DEGRADATION OF A THERMAL BARRIER COATING DUE TO HOT CORROSION

Degradation of a thermal barrier coating (TBC), consisting of NiCrAlY as bottom layer and ZrO2·8%Y2O3 as top layer, on superalloy K3 under hot corrosion condition was studied. The coating was obtained successively by DC magnetron sputtering and RF magnetron sputtering. SEM metallography and XRD were used to examine the change of the morphology of coating surface, coating/ substrate interface and corrosion products. The ceramic top layer in TBC considerably improved its hot corrosion resistance. There were two reasons to cause degradation of TBC. First, the fused salt penetrated along grain boundaries of the ceramic top layer and attacked its bottom layer. Second, acid dissolution of Y2O3 promoted transformation of ZrO2 from cubic (C) phase to monoclinic (M) phase. Some technical faults might lead to premature catastrophic failure of TBC.