Residual stress measurement of physical vapor deposition (PVD) AlTiN thin films - a comparative study of x-Ray diffraction-, Raman spectroscopic and ring core method

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Abstract Cutting inserts experience substantial mechanical and thermal loads during machining. Hard thin-film coatings are widely applied to enhance performance and durability, but their residual stresses critically affect adhesion, stability, and tool life. Common stress determination methods include X-ray diffraction (sin²ψ; V m; XRD = 1.3–2.6 mm×3.7 μm), focused ion beam-digital image correlation (FIB-DIC) ring core method ( V m; FIB/DIC = 10 μm×3.7 μm), and Raman spectroscopy ( V m; Raman = 1 μm×40 nm), each deviating in measured volume ( V m = spot size × depth). Our comparative study examines different instrumentation, analysis tools, and applied methods for evaluating residual stresses in physical vapor deposition (PVD)-coated carbide inserts. Results disclose varying susceptibilities depending on thin film characteristics such as thickness, film-substrate interface, texture, chemical and residual stress gradients, highlighting differences in information depth and sensitivity. The study provides a good overview of laboratory methods for determining residual stresses in PVD coating. The sin²ψ-method provides reproducible residual stress states that are independent of varying instruments or analytical methods, including calibrants, radiation, different optics, detectors and even evaluated reflections and are more strongly affected by texture and residual stress gradient. FIB-DIC and sin²ψ method consider the entire cross-section and agree well. FIB-DIC offers higher spatial resolution and is more sensitive to nonuniform chemical influences. In Raman spectroscopy, the bond strength is affected by chemical gradients, among other factors, necessitating an elaborate calibration. Its low penetration depth of a few nanometers and the small spot size cause deviations in the studied heterogeneous thin films.

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