Evaluation method for the interfacial strength of thermally grown Al2O3 scale and Ni-Al alloy

Chihiro Tabata; Taiyo Maeda; Thomas Hoefler; Shingo Ozaki; Kyoko Kawagishi; Shinsuke Suzuki; Takahito Ohmura; Toshio Osada

doi:10.1016/j.matdes.2026.116448

Journal article Evaluation method for the interfacial strength of thermally grown Al2O3 scale and Ni-Al alloy

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Chihiro Tabata, Taiyo Maeda, Thomas Hoefler, Shingo Ozaki, Kyoko Kawagishi, Shinsuke Suzuki, Takahito Ohmura, Toshio Osada. Evaluation method for the interfacial strength of thermally grown Al2O3 scale and Ni-Al alloy. Materials & Design. 2026, 268 (), 116448. https://doi.org/10.1016/j.matdes.2026.116448

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Nanoindentation techniques are useful for evaluating the critical load for crack initiation on interface between Ni-Al alloy and thin surface Al2O3 scale formed at high temperature, since interfacial cracking can be clearly detected as a pop-in event. However, actual interfacial stress applied during loading and when cracked is unclear, due to the multiaxial stress field. Here we analyzed interfacial stress distribution during the nanoindentation using finite element analysis. Elastoplastic simulations of nanoindentation were performed with local stress-strain curves for oxide scale and the Al depletion zone. Local stress-strain curves were inversely analyzed from experimental load-penetration depth curves, obtained using separate nanoindentation tests. Interfacial stress was obtained as a function of indentation load, clarifying that shear stress acting on interface contributed significantly to crack initiation. The two-parameter Weibull plots of interfacial strength σ_(Int,max)^c were converted from pop-in load Pc obtained in experimental nanoindentation tests for samples with different amounts of impurity S segregation. Largest differences appear where fracture probability F is low; for F=4%, difference of approximately 780 MPa between the sample with higher S segregation level (high Sinterface alloy, σ_(Int,max)^c=1.73 GPa) and lower S segregation level (low Sinterface alloy, σ_(Int,max)^c=2.51 GPa) were obtained.

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