Residual stress was measured on plasma sprayed crystalline Ni\Al, Al2O3 and amorphous Al2O3\TiO2\ZrO2-CeO2 single splats, by using an incremental focused ion beam (FIB) micron-scale ring-core method (IμRCM).Tensile residual stress exists in polycrystalline Ni\Al splats, where the quenching stress is only partially relaxedby edge curling and through-thickness yielding. Significant compressive stress was observed for theamorphous Al2O3\TiO2\ZrO2\CeO2 splats, where viscous flow above the glass transition temperaturecompletely relaxed the quenching stresses without micro-cracking. Comparatively lower compressive stresswas measured on crystalline Al2O3 splats, where, in spite of extensive micro-cracking, not all of the tensilequenching stress was relaxed. Using stress data and micro-crack geometry, the intrinsic shear adhesionstrength of Al2O3 splats was calculated, giving insights into the role of (sub)micron-scale phenomena onadhesion/cohesion of thermally sprayed coatings. The proposed stress build-up mechanisms and relaxationphenomena are supported by a TEM microstructural analysis of the splats.The experimental methodology developed provided a unique way for the study of the residual stress buildupmechanisms in amorphous and crystalline single splats obtained by plasma spraying, and gave further insightsinto the actual micro-scale phenomena that give rise to adhesion and nano-mechanical behavior ofthermally sprayed coatings.The proposed approach is also expected to find a wide range of applications in materials science and engineering,as it allows for the residual stress measurement even on amorphous materials with micrometer spatialresolution.
High resolution residual stress measurement on amorphous and crystalline plasma-sprayed single-splats / M., Sebastiani; Bolelli, Giovanni; Lusvarghi, Luca; P. P., Bandyopadhyay; E., Bemporad. - In: SURFACE & COATINGS TECHNOLOGY. - ISSN 0257-8972. - STAMPA. - 206(23):(2012), pp. 4872-4880. [10.1016/j.surfcoat.2012.05.078]