High temperature corrosion behaviour of a gradient NiCoCrAlYSi coating II: Oxidation and hot corrosion

The high temperature oxidation and hot corrosion behaviour of a NiCoCrAlYSi coating and a gradient coating were investigated. The gradient coating showed better performance of re-healing alumina scale due to its possession of more beta phase as Al reservoir. The degradation process of the gradient coating was favorably retarded by the formation of Cr(W)-rich sigma precipitates in the interdiffusion zone. The corrosion results also confirmed an improved corrosion resistance of the gradient coating. The improved high temperature performance of the gradient coating owes to the Al enrichment of Al in the outer layer. (C) 2010 Elsevier Ltd. All rights reserved.