Determining and predicting the flank wear width and residual stress of coated tools by Raman imaging

Tool wear monitoring remains critical for modern machining, yet current methods face significant limitations in spatial resolution and sensitivity. This study presents a novel approach using Raman imaging to simultaneously determine flank wear width and residual stress of TiAlN-coated cutting tools with sub-micrometer resolution. We moreover develop a grey-box modeling framework that integrates white-box knowledge from density-functional theory calculations of transverse acoustic (TA) phonon modes with black-box empirical data from experimental Raman mappings. Raman imaging with 0 . 45 μ m spatial resolution on worn flanks of TiAlN-coated carbide tools reveals three distinct zones: highly amorphous substrate material at the cutting edge, intact TiAlN coating, and adhered Fe 2 O 3 from oxidized workpiece material. A recovery of the TA mode intensity indicates a percolation of crystalline domains at the first zone interface. The compressive residual stress ranges from ( − 1 . 7 ± 0 . 2 ) GPa in the intact coating to peaks of approximately − 5 GPa at the second interface. This sharp drop in residual stress and a broadening of the TA phonon linewidth by about 15% indicate subsurface modifications before visible wear appears. For a tool operation time of t = 80 % , the flank wear width measured to VB Raman = ( 75 . 0 ± 1 . 2 ) μ m shows excellent agreement with optical measurements. The grey-box model successfully predicts wear progression of the TiAlN coating and the spatial distribution of the residual stress at the tool flank using a power law for the temporal evolution of the flank wear width. It demonstrates superior predictive capability for the wear assessment of coated tools in advanced machining applications. • Raman imaging simultaneously determines flank wear width and residual stress of TiAlN-coated cutting tools with sub-micrometer resolution. • Raman imaging reveals three distinct zones at the tool flank: highly amorphous substrate material at the cutting edge, the intact TiAlN coating, and adhered Fe 2 O 3 from oxidized workpiece material. • Subsurface degradation detected 5–10 μ m (before appearance of visible wear) through 15% TA phonon broadening and stress peaks at −5 GPa. • Flank wear width VB (75.0 ± 1.2 μ m at t = 80%) shows excellent agreement with optical measurements. • Grey-box model combining DFT calculations with empirical power law (VB = α ⋅ t β ) successfully predicts wear progression and stress distribution.