High resolution residual stress measurement on amorphous and crystalline plasma-sprayed single-splats

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• 作者：M. Sebastiani ; G. Bolelli ; L. Lusvarghi ; P.P. B ; yopadhyay ; E. Bemporad
• 关键词：Residual stresses ; Amorphous materials ; Splat quenching ; Plasma spraying ; Focused ion beam (FIB)
• 刊名：Surface and Coatings Technology
• 出版年：2012
• 出版时间：15 July, 2012
• 年：2012
• 卷：206
• 期：23
• 页码：4872-4880
• 全文大小：1719 K

文摘

Residual stress was measured on plasma sprayed crystalline NiAl, Al₂O₃ and amorphous Al₂O₃TiO₂ZrO₂CeO₂ single splats, by using an incremental focused ion beam (FIB) micron-scale ring-core method (I¦ÌRCM).

Tensile residual stress exists in polycrystalline NiAl splats, where the quenching stress is only partially relaxed by edge curling and through-thickness yielding. Significant compressive stress was observed for the amorphous Al₂O₃TiO₂ZrO₂CeO₂ splats, where viscous flow above the glass transition temperature completely relaxed the quenching stresses without micro-cracking. Comparatively lower compressive stress was measured on crystalline Al₂O₃ splats, where, in spite of extensive micro-cracking, not all of the tensile quenching stress was relaxed. Using stress data and micro-crack geometry, the intrinsic shear adhesion strength of Al₂O₃ splats was calculated, giving insights into the role of (sub)micron-scale phenomena on adhesion/cohesion of thermally sprayed coatings. The proposed stress build-up mechanisms and relaxation phenomena 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 build-up mechanisms in amorphous and crystalline single splats obtained by plasma spraying, and gave further insights into the actual micro-scale phenomena that give rise to adhesion and nano-mechanical behavior of thermally 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 spatial resolution.