Evaluation of induction thermography for the detection of cracks due to mechanical and thermal stress in WC-10Co-4Cr coatings

WC-Co-Cr coatings have exceptional mechanical properties including high hardness, wear resistance and corrosion resistance. However, under continuous wear or mechanical/thermal overloads, such as line loads in calender rollers or improper heating/cooling cycles, these coatings can develop defects like cracks and dents. Such damage compromises product quality, particularly in calendering processes where precise roller concentricity (single-figure micrometre range) is critical. This study investigates induction thermography as a non-destructive alternative for defect detection in WC-10Co-4Cr coatings. Coated C60 steel specimens with different surface roughness (conditions: ground and as-sprayed) were subjected to controlled mechanical (strains: 0.12–0.4%) and thermal stresses (thermal shock), inducing cracks in the range of approx. 1–4.5 µm in width. Using the Fourier transform method and principal component analysis, induction thermography successfully identified cracks with a width of ≈ 1 µm under both conditions, demonstrating its sensitivity to defect detection across different surface conditions. The results highlight the potential of this method to improve process reliability and product quality in high-precision applications by enabling non-invasive, real-time inspection.