Tensile behavior of air plasma spray MCrAlY coatings: Role of high temperature aging and process defect

International audienceMCrAlY coatings are used as a protection layer against high temperature oxidation and corrosion for components working in an aggressive environment. In order to predict both coating and substrate lifetime, the characterization of thermomechanical properties of the coating is a challenging issue [1-3]. As these coatings are only a few hundreds of micrometers thick, their properties should be investigated with experimental tests adapted at this small scale [1-4]. In the present study, the mechanical properties of a free-standing MCrAlY coating and their evolution were scrutinized when it is aged in air for a large range of time and temperature. Free-standing micro-tensile specimens were prepared [1] and tested after different time/temperature ageings [4]. Based on digital image correlation to derive the strain evolution during loading, the stress-strain behavior has been identified. Thus a crucial effect of intrusive oxidation from deposition process defects and surface oxidation has been evidenced to drive both the ductility and the fracture mechanism of the tested material. For coarse intrusive oxidation, a loss of ductility has been identified, whereas metallic phase transformation (from to ) increases the ductility of the material from 0.5 up to 3%. This composite effect will be analyzed through systematic microstructure and homogenization analyses. This methodology could be straightforward to determine the coupling between coating cracking and substrate failure under thermo-mechanical fatigue conditions [5].References[1] D. Texier, D. Monceau, J. C. Salabura, R. Mainguy, E. Andrieu, Materials at High Temperatures, 33 (2016) 325–337.[2] D. Texier, D. Monceau, Z. Hervier, E. Andrieu, Surface and Coatings Technology, 307 (2017) 81–90 [3] Alam, M.Z., Satyanarayana, D.V.V., Chatterjee, D., Sarkar, R., Das, D. K., Materials Science and Engineering: A, 641 (2015) 84-95.[4] Straub, T., Baumert, E.K., Eberl, C., Pierron, O.N., Thin Solid Films, 526 (2012) 176–182.[5] Esin, V.A., Maurel, V., Breton, P., Köster, A., Selezneff, S., Acta Materialia, 105 (2016) 505–518