Failure Map generation by NDT on Metal Sprayed Multi-surfaces

Abstract

This thesis focuses on the development and evaluation of a methodology for defect detection in thermally sprayed metallic coatings using non-destructive eddy-current testing (ECT). The main objective was to create a reliable approach for transforming raw measurement data into clear and interpretable three-dimensional failure maps, improving the practical usability of NDT results . The study includes an overview of thermal spray technologies and typical failure modes such as cracks, delamination, and porosity. Based on the electrical conductivity of the materials, the eddy-current method was selected due to its sensitivity to surface and near-surface defects. An experimental setup was developed using a Foerster Defectometer M 1.837 with computer-based data acquisition. A structured measurement methodology was established, including calibration, selection of scanning patterns, and optimization of parameters. A linear parallel scanning strategy was applied to ensure consistent data collection and accurate spatial reconstruction. The data were processed using spreadsheet tools, where invalid values were removed and a failure index was introduced for defect evaluation. Three-dimensional failure maps were generated for multiple specimens, allowing visualization and comparison of defect distribution. The results showed defect densities ranging from approximately 5.6% to 13.6%, confirming the capability of the method to distinguish coating quality. The study also identified limitations related to probe lift-off, surface roughness, and operator influence. Despite these challenges, the developed methodology provides a practical tool for defect assessment. Future improvements may include automation, advanced data analysis techniques, and methodological enhancements, supporting potential industrial applications in quality control and maintenance.