Laser shock peening (LSP) was applied to WC–Co cemented carbides with Co contents from 6 to 13 wt% to elucidate the phase-specific strengthening mechanism and its impact on tool wear resistance. Under optimized conditions (100 mJ, 400 μm spot, 30 passes), surface hardness improved by 40–50 HV for WC–10 wt%Co, with the strengthened layer extending beyond 100 μm. The hardness increment correlated positively with Co content, suggesting the ductile binder as the primary site of strengthening. Microstructural analysis and nanoindentation provided phase-resolved evidence that Co-phase work hardening is a significant contributing mechanism in the LSP response. Turning tests on LSP-treated tools demonstrated a 50% reduction in flank wear and a 40% reduction in crater wear at a cutting speed of 110 m/min. This improvement is attributed partly to the enhanced resistance of the work-hardened Co binder to plastic deformation-driven grain pull-out, with possible contribution from LSP-induced compressive residual stress. However, the effectiveness diminished at 150 m/min, where thermal wear mechanisms prevail. Comparisons between as-treated and polished tools suggested that the wear resistance improvement arises predominantly from subsurface strengthening rather than the surface-melted layer. These findings demonstrate the potential of LSP as a substrate-level enhancement strategy for cemented carbide cutting tools.
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