Initiation and propagation of interfacial cracks during spontaneous debonding of thermally sprayed coatings
- Cambridge Univ. (United Kingdom)
Spontaneous debonding of alumina coatings sprayed onto mild steel substrates has been investigated experimentally and theoretically. Residual stress states generated during spraying and subsequent cooling have been predicted using a numerical model and validated experimentally. For any given residual stress state, the strain energy release rate, G{sub r}, can be calculated for interfacial debonding by evaluating the associated change in stored elastic strain energy. The magnitude of G{sub r} at which specimens were observed to debond spontaneously have been taken as critical strain energy release rate, G{sub ic}, ie interfacial fracture energy, values. For a variety of coating thicknesses and substrate temperatures, values of G{sub ic} obtained in this way all fell in the range of 400--500 J m{sup {minus}2}. Corresponding values of the phase angle, {Psi}, (characterizing the mode mixity) were all in the range 70--90. The consistency of these G{sub ic} values is encouraging, but this method of evaluation is based on analysis of the propagation, rather than initiation, of the interfacial crack. Similar experiments were therefore performed on specimens with interfacial pre-cracks of various lengths. The value of G{sub ic} was found to decrease somewhat with increasing length of pre-crack, indicating that debonding was initiation-controlled. These results are considered in the light of theoretical models for initiation of substrate/coating interfacial cracks.
- OSTI ID:
- 379547
- Report Number(s):
- CONF-9509182-; ISBN 0-87170-541-9; TRN: IM9644%%3
- Resource Relation:
- Conference: 1995 National thermal spray conference, Houston, TX (United States), 11-15 Sep 1995; Other Information: PBD: 1995; Related Information: Is Part Of Advances in thermal spray science and technology. Proceedings of the 8. national thermal spray conference; Berndt, C.C.; Sampath, S. [eds.]; PB: 795 p.
- Country of Publication:
- United States
- Language:
- English
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