Abstract
Residual stresses of physical vapor deposition (PVD) hard coatings can be measured using X-ray diffraction (XRD) methods under either conventional d-sin2 ψ mode or glancing incident (GIXRD) mode, in which substantial uncertainties exist depending on the applied diffraction parameters. This paper reports systematic research on the effect of the two analytical modes, as well as the anisotropic elastic modulus, on the measured residual stress values. A magnetron sputtered TiN grown on hardened tool steel was employed as the sample coating, to measure its residual stress using various diffraction peaks from {111} to {422} acquired at a range of incident glancing angles from 2° to 35°. The results were interpreted in terms of the effective X-ray penetration depth, which has been found to be determined predominantly by the incident glancing angle. In the d-sin2 ψ mode, the results present an approximate residual stress over a depth of effective X-ray penetration, and it is recommended to use a diffraction peak of high-index lattice plane from {311} to {422}. The GIXRD mode helps determine a depth profile of residual stress, since the measured residual stress depends strongly on the X-ray penetration. In addition, the anisotropy of elastic modulus shows limited influence on the calculated residual stress value.
Highlights
Most hard coatings grown by plasma enhanced physical vapor deposition (PVD) show various levels of residual stresses which strongly influence the adhesion and tribological performance
In the conventional sin2 ψ measurement, a crystal plane, usually having a high diffraction angle (2θ > 125◦ ), is selected as the strain gauge that a series of ψ angles can be obtained by acquiring its diffraction peaks at different incident angles, Ω, of the X-ray beam [4,5]
It is expected that the results presented could help improve understanding about the accuracy in X-ray diffraction (XRD) residual stress measurements, the selection of appropriate diffraction parameters
Summary
Most hard coatings grown by plasma enhanced physical vapor deposition (PVD) show various levels of residual stresses which strongly influence the adhesion and tribological performance. For the former, the uncertainties may result and ψ angles and the structural heterogeneity of the films and coatings to be measured From both the dependence of X-ray penetration on the applied diffraction geometry, i.e., the Ω and different crystalline planes, from the low‐index planes {111} and {200}, to the high‐index planes {311}. Series of on Ωangles have been employed to acquire peaks arising of crystalfrom to allow study to beAfocused the uncertainties of residual stress diffraction measurements the selection of XRD parameters. For this purpose, a magnetron sputtered titanium nitride coating. To interpret the obtained results, the relationship between the X‐ray penetration depth and the intensity of the diffracted X‐ray beam has been
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