# Surface Topography of Hardened Stainless Steel in Dry Finish Turning Using CBN and Cemented Carbide Inserts

## TL;DR

This study examines how different cutting tools and parameters affect the surface quality of hardened stainless steel during machining.

## Contribution

The study provides new insights into the surface topography of hardened stainless steel machined with CBN and CC inserts under dry conditions.

## Key findings

- Feed rate is the dominant factor influencing surface roughness parameters Sa and Sq for both CBN and CC inserts.
- CBN inserts produce a more regular surface topography, while CC inserts result in a wavy surface due to plastic deformation.
- Low Sa values (0.4–0.6 µm) can be achieved, potentially eliminating the need for grinding operations.

## Abstract

The proper selection of surface topography (ST) parameters is crucial for ensuring the effective performance of machine components, including their wear and corrosion resistance. In the literature, research on the ST of hardened stainless steels (SSs) after finish turning using cubic boron nitride (CBN) inserts, as well as comparisons with cemented carbide (CC) inserts depending on cutting parameters, is still limited. In this study, the ST of X20Cr13 martensitic hardened SS under dry finish turning with various cutting speeds and feed rates was investigated. Experiments were conducted using a CNC lathe with CBN and CC inserts. A Sensofar S Neox 3D optical profilometer was employed to characterize the ST features, including height surface roughness (SR) parameters, SR profiles, and 2D and 3D surface images. The Parameter Space Investigation method was used to design the experimental plan. For both CBN and CC inserts, the feed rate was the dominant factor influencing the overall SR, described by the Sa and Sq parameters. The extreme parameters Sp, Sv, and Sz were determined by the relationship between feed rate and cutting speed. With appropriately selected turning parameters, it is possible to obtain low Sa values (0.4–0.6 µm), which can eliminate the need for grinding operations. CBN inserts ensured a more regular shape of the ST, while CC inserts contributed to a wavy surface characteristic, associated with more intense plastic deformation. However, low Sa values may be accompanied by isolated peaks, indicating that this parameter does not always fully reflect the presence of extreme micro-irregularities. On the machined surfaces, adhesive bonds of chips and cutting tool material were observed. In addition, micro-scratches were registered for CBN inserts, and a side flow phenomenon for CC inserts. The results confirm that dry turning of hardened SSs can be effectively performed using both CC and CBN inserts.