High-Resolution Depth Profiling of Residual Stresses in PVD Coatings on Additively Manufactured Polymers via FIB-DIC and Eigenstrain Theory

TL;DR

This study uses advanced techniques to analyze residual stresses in PVD coatings on 3D-printed polymers, revealing critical stress patterns that affect reliability.

Contribution

The first high-resolution nanoscale profiling of residual stresses in PVD coatings on additively manufactured polymers using FIB-DIC and eigenstrain theory.

Findings

Compressive stresses are observed near the coating surface, while a tensile stress peak occurs at the coating-substrate interface.

A thin, brittle oxide interlayer on the polymer substrate is linked to stress concentration.

Low-stiffness polymer substrates cause significantly higher strain relief compared to rigid substrates.

Abstract

The synergy between additively manufactured (AM) polymers and functional PVD coatings is crucial for advanced applications, yet the reliability of these hybrid systems is dictated by the residual stresses induced during deposition. This work presents the first in-depth, nanoscale profiling of residual stresses in Ti6Al4V and SS316 coatings on 3D-printed Acrylonitrile Styrene Acrylate (ASA) and Silicon (Si) substrates. A cutting-edge methodology combining Focused Ion Beam (FIB) milling with Digital Image Correlation (DIC), rigorously interpreted through the non-integral eigenstrain theory, is employed. Our findings reveal a consistent pattern of compressive stresses near the coating surface but expose a significant tensile stress peak at the coating-substrate interface, a feature not observed on reference silicon substrates. High-resolution electron microscopy and elemental analysis suggest that this stress concentration is associated with the presence of a thin, brittle oxide interlayer formed on the substrate surface. Furthermore, this study quantifies the dominant effect of the low-stiffness polymer substrate, which leads to a strain relief magnitude an order of magnitude higher than in rigid substrates. This work provides critical quantitative data on the failure-driving mechanisms in these emerging material systems and establishes a robust, optimized metrological protocol for their characterization.

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