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- Hahn, R., et al.
(författare)
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Unraveling the superlattice effect for hexagonal transition metal diboride coatings
- 2023
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Ingår i: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 235
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Tidskriftsartikel (refereegranskat)abstract
- Superlattice structures enable the simultaneous enhancement in hardness (H) and fracture toughness (KIC) of ceramic-like coatings. While a deeper understanding of this effect has been gained for fcc-structured transition metal nitrides (TMN), hardly any knowledge is available for hexagonal diborides (TMB2). Here we show that superlattices can-similarly to nitrides-increase the hardness and toughness of diboride films. For this purpose, we deposited TiB2/WB2 and TiB2/ZrB2 superlattices with different bilayer periods (?) by non-reactive sputtering. Nanoindentation and in-situ microcantilever bending tests yield a distinct H peak for the TiB2/WB2 system (45.5 & PLUSMN; 1.3 GPa for ? = 6 nm) but no increase in KIC related to a difference in shear moduli (112 GPa). Contrary, the TiB2/ZrB2 system shows no peak in H, but for KIC with 3.70 & PLUSMN; 0.26 MPa & BULL;m1/2 at ? = 4 nm originating from differences in lattice spacing (0.14 & ANGS;), hence causing coherent stresses retarding crack growth.
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