Cross-sectional X-ray nanodiffraction reveals nanoscale residual stress and microstructure gradients across the cutting edge area of a TiN coating on WC-Co

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Beschreibung

The nanoscale microstructural and residual stress gradients across hard coatings along the edges of cutting tools are of tremendous scientific and industrial interest. In this work, cross-sectional X-ray nanodiffraction with a beam size of 25×35 nm² was used to assess the structural and mechanical gradients in the cutting edge area of a up to 2.5 μm thick TiN coating deposited by cathodic arc evaporation on a WC-Co cutting insert. Scanning electron microscopy revealed a dense columnar-grained coating at the edge with the TiN columns oriented parallel to the edge surface normal. Additionally, nanosized pores were found at the rake face of the insert. Small-angle X-ray scattering (SAXS) microscopy is used for the first time to qualitatively investigate the nanoscale defect density in the cutting edge area. Directly at the edge, interface-like planar domains of high scattered intensity were indicated, while a gradual increase of the SAXS intensity at the rake face was correlated with pores found by scanning electron microscopy. Furthermore, the coating’s ├ ⟨111┤⟩ fibre texture axis orientation correlates with the edge’s surface normal, showing abrupt orientation changes across the former mentioned interface-like structures. Furthermore, the fibre texture orientation correlates locally with the principal stress tensor used for the evaluation of residual stress along the cutting edge. The planar regions next to the edge exhibit gradual and constant stress profiles with anisotropic defect build-ups on the flank and rake faces, respectively. Directly at the edge, nonlinear lateral and cross-sectional compressive residual stress gradients ranging from ~0 to −3 GPa were observed, which together with the interface-like planar domains may represent a reliability issue during operation.
Zeitraum28 März 2022
EreignistitelICRS11 - The 11th international conference on residual stress
VeranstaltungstypKonferenz
OrtNancy, FrankreichAuf Karte anzeigen
BekanntheitsgradInternational