Damage mechanisms in solid particle impact and erosion testing of thermal barrier coatings

Abstract

The ability of both cyclic and randomly spatially-distributed impact tests of columnar EB-PVD ceramic thermal barrier coating (TBC) systems with yttria stabilised zirconia (YSZ) and gadolinium zirconate (GZO) topcoats to simulate their behaviour in solid particle erosion tests has been investigated. The impact tests were able to replicate the main mechanisms and surface morphology in the erosion tests although there was more compaction in the impact tests. Densification below impact craters on YSZ and sub-surface cracking between the dense layer and the un-densified columns were revealed by focussed ion beam milling. Cracking over several columns and break-up of the columnar structure was observed in the impact and erosion tests on GZO. Clear differences in TBC erosion rate, with GZO being much less resistant to erosion, were replicated in the cyclic and randomly spatially-distributed micro-impact tests.