Ubiquity Proceedings (Sep 2018)
SSTT2018 Swansea University Experimental investigations on the failure of a coating-substrate compound by means of the C-specimen concept and the small punch test
Abstract
In previous work at the Institute of Mechanics and Fluid Dynamics of the TU Bergakademie Freiberg the thermomechanical fatigue of corrosion protection coatings was investigated, which had been manufactured by high velocity oxygen fuel spraying (HVOF) of a nickel-base superalloy. The failure behaviour of this coating-substrate compound under thermomechanical cyclic service loading is characterised by the combination of multiple damage mechanisms. During the course of the project, two dominant damage mechanisms were identified, that result in a functional failure of the coating. The first significant damage mechanism is the formation of delamination areas between coating and substrate, which result in local coating spallings, if they reach a critical size. The second important damage mechanism is the initiation and the propagation of inter-particle cracks in the coating. Regarding the functionality of the corrosion-preventive coating, these cracks become critical if they extend across the whole layer thickness up to the substrate. In order to further investigate the interface delamination between coating and substrate, the so-called C-specimen concept (CSC) has been developed. The characterisation of the inter-particle failure of the pure coating on the other hand is realised by the small punch test (SPT). In this contribution, both possible sources of the coating-substrate compound failure behaviour are addressed and have been experimentally examined by the use of the CSC and the SPT. These tests were conducted with the purpose of building a sufficiently detailed experimental data base suitable for the parameter identification of cyclic cohesive zone-based failure models.
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