**2.2 Characterization**

The surface roughness of burnished surfaces was measured using Altisurf500 profilometer (**Figure 2**(1)). For each sample, an area of 3 × 2 mm2 was scanned with a cutoff length of 0.8 mm. Altimap software was used to extract the following surface texture parameters. Atomic force microscopy (Bruker Dimension) was used to analyze the 3D topography of some selected surfaces.

Innovatest microdurometer, showed in **Figure 2**(2), was used to measure the surface microhardness of pre-machined and burnished samples. All tests were carried out using a load of 100 kgf applied for 10 s. The average diameters of five indentations were calculated to get reliable data.
