Patent ID: 7357994

Claim:
A coating system on an article having a substrate formed of a silicon-containing material, the coating system comprising: a silicate-containing coating overlying the substrate and containing at least one silicate susceptible to corrosion; a thermal barrier coating overlying the silicate-containing coating and formed of a thermal-insulating material having a coefficient of thermal expansion (CTE) different than the silicate-containing coating; and a transition layer between the silicate-containing coating and the thermal barrier coating, the transition layer providing corrosion protection to the at least one silicate of the silicate-containing coating and providing a CTE mismatch-abating transition between the silicate-containing coating and the thermal barrier coating, the transition layer being free of silicates and consisting essentially of at least one aluminate compound and optionally containing the thermal-insulating material and/or alumina, the at least one aluminate compound being chosen from the group consisting of YAlO 3 , Y 3 Al 5 O 12 , NbAlO 4 , TaAlO 4 , SrAl 2 O 4 , CaAl 2 O 4 , CaAl 4 O 7 , SrLaAlO 3 , MgAl 2 O 4 , ScAlO 3 , and rare earth aluminate compounds: wherein to enable the transition layer to provide a CTE mismatch-abating transition between the silicate-containing coating and the thermal barrier coating, the transition layer: consists essentially of the at least one aluminate compound and the CTE of the transition layer is a value between the CTE's of the thermal-insulating material and the silicate-containing coating; or is a substantially homogeneous mixture consisting essentially of the at least one aluminate compound and at least one of the thermal-insulating material and the alumina, and the CTE of the transition layer is a value between the CTE's of the thermal-insulating material and the silicate-containing coating; or is a compositionally graded mixture consisting essentially of the at least one aluminate compound and at least one of the thermal-insulating material and the alumina, and has a gradually increasing CTE with a minium CTE value adjacent the silicate-containing coating and a maximum CTE value adjacent the thermal barrier coating.