Turning-induced surface integrity for a fillet radius in a 316L austenitic stainless steel

Abstract

Turning is a machining process extensively applied to produce revolution parts. Durability of these parts are known to depend on the turning process signature that is often referred as surface integrity. The surface integrity generated in a fillet radius has been barely studied in the literature so far, despite the well-known geometrical stress concentration factor of such singularities. Therefore this paper deals with the investigation of machining-induced surface integrity when turning a fillet radius in a 316L austenitic stainless steel. Different characterization methods are used for that purpose - SEM, EBSD, nanoindentation and X-Ray diffraction. It points out that the turning-induced consequences are not homogeneous along the machined profile. Residual stresses are strongly affected and microstructure is highly modified over a depth of 80 μm that leads to a mechanical properties gradient. It is evidenced that the average uncut chip thickness is the main governing parameter regarding surface integrity. It is also reported that deformation twins appear in the affected zone. It highlights that turning-induced microstructure evolution at a given depth is rather a consequence of severe plastic deformation at high strain rate than dynamic recrystallization. • For the first time, turning-induced surface integrity in 316L is studied along a fillet radius. • Turning-induced affected depth depends on angular position in the fillet radius. • Affected depth is twice larger for longitudinal turning than for face turning. • Microstructure evolution is correlated with average uncut chip thickness parameter and cutting edge radius. • Severe plastic deformation at room temperature or/and high strain rate governs microstructural evolution (deformation twins).