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@ARTICLE{Zhang:1047159,
      author       = {Zhang, Yinxia and Bartosik, Matthias and Brinckmann,
                      Steffen and Lee, Subin and Kirchlechner, Christoph},
      title        = {{T}oughening nitride hard coatings by deflecting cracks
                      along grain boundaries},
      journal      = {Materials science $\&$ engineering / A},
      volume       = {935},
      issn         = {0921-5093},
      address      = {Amsterdam},
      publisher    = {Elsevier},
      reportid     = {FZJ-2025-04116},
      pages        = {148392},
      year         = {2025},
      abstract     = {Grain boundaries (GBs) in hard coatings are often
                      considered as the weakest link, acting as preferred pathways
                      for crack propagation and thereby limiting the coating's
                      fracture toughness. In this study, we investigate whether
                      continuous crack deflection along GBs can mitigate this
                      limitation and enhance the fracture resistance of hard
                      coatings. Three model systems were examined: CrN, AlN and
                      their multilayered structure coatings, all characterized by
                      columnar GB structures. Fracture toughness was
                      quantitatively assessed using an in situ SEM
                      micro-cantilever fracture testing. The key approach of this
                      study is the use of two different loading geometries, with
                      notches aligned either parallel or perpendicular to the
                      coating's growth direction, allowing us to compare the
                      influence of the crack propagation direction and deflection.
                      Across all three systems, the perpendicular notch
                      configuration—aligned across the columnar
                      microstructure—resulted in approximately 8 $\%$ higher
                      fracture toughness. This enhancement is attributed to
                      continuous crack deflection along GBs during deformation.
                      Additionally, the extent of crack deflection was found to
                      depend on the local GB arrangement, with transgranular
                      fracture observed when no well-aligned GBs were present
                      along the crack path. These findings provide quantitative
                      insights into the toughening mechanisms enabled by
                      GB-mediated crack deflection and offer design strategies for
                      mechanically robust hard coatings.},
      cin          = {IMD-1},
      ddc          = {530},
      cid          = {I:(DE-Juel1)IMD-1-20101013},
      pnm          = {1241 - Gas turbines (POF4-124)},
      pid          = {G:(DE-HGF)POF4-1241},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.1016/j.msea.2025.148392},
      url          = {https://juser.fz-juelich.de/record/1047159},
}