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Interest in hard-turning is steadily increasing due to its obvious benefits in terms of desirable surface integrity and improved operational efficiency. Surface microstructural variations can occur during machining due to cutting speed, tool geometry, and process conditions. Th ese variations create nanostructured white layers (WL), categorized as mechanically induced white layers (M-WL) or thermally induced white layers (T-WL). This study explored the role of retained austenite (RA) content (<2%, 12%, and 25%) on WL generation in AISI 52100 bearing steel, offering insights for optimizing hard-turning. The findings showed that, regardless of RA content, samples exhibited M-WL with no dark layer beneath the white layer when utilizing a cutting speed (VC) of 60m/min using a fresh insert. Increasing tool flank wear to 0.2mm led to the formation of T-WL and surface tensile residual stresses in specimens with higher RA content (12% and 25%). This effect was also observed at 260m/min with a fresh cutting insert. Machining at 260m/min with a worn tool (VB) of 0.2mm resulted in T-WL and surface tensile residual stresses, independent of RA content. Additionally, a 0.2mm tool wear caused a significant shift in the maximum subsurface compressive residual stre sses to greater depths, irrespective of RA content., Conference name: 7th CIRP Conference on Surface Integrity, CSI 2024; Conference date: 15 May 2024 through 17 May 2024; Conference code: 200295; All Open Access, Gold Open AccessThe study is part of the Turn2Flex (Vinnova 2021-01274) project and the HybridSurf (Vinnova 2018-04263) project financed by the Swedish government agency for Enterprise and Innovation. We especially thank AB SKF, Ovako AB, and Sumitomo Electric Hartmetall GmbH for supporting with machining and material support.