Simulation Study on the Instability of Microscopic Columnar Structures in TiN Coatings Prepared by Magnetron Sputtering

To clarify the instability behavior of the columnar microstructure in RF magnetron sputtered TiN coatings under compressive loading, experimental characterization and finite element simulation were combined to investigate the microstructural features, mechanical properties, and linear and nonlinear buckling responses of the coating. TiN coatings were deposited on cemented carbide and Si substrates by RF magnetron sputtering using a 99.9% purity TiN target. The surface and cross-sectional morphologies were characterized by field-emission scanning electron microscopy, and the nanohardness and Young’s modulus were determined by nanoindentation. Based on the experimentally observed morphology and measured mechanical properties, a finite element model of the columnar structure was established in ABAQUS, and the instability responses predicted by solid, shell, and beam element models were comparatively analyzed. The results showed that the as-deposited TiN coating exhibited a dense and uniform surface and a distinct columnar microstructure in cross-section. Linear buckling analysis indicated that the first-order critical buckling loads predicted by different element models were different, among which the solid element model gave a value of 3.43 × 10−5 N, showing the closest agreement with the theoretical result. Furthermore, nonlinear buckling analysis was performed by introducing an initial geometric imperfection of 4 × 10−3 mm based on the first-order buckling mode of the solid element model. The results showed that the columnar structure became unstable at a load of 0.74 × 10−6 N, accompanied by irreversible deformation. These findings demonstrate that linking experimentally observed TiN columnar microstructures with microstructure-informed instability analysis provides a useful perspective for understanding the local instability behavior and potential failure tendency of sputtered coatings and offers theoretical support for the structural design and reliability evaluation of protective coatings for cutting tools.