**2. Experimental**

## **2.1 Ball burnishing treatment**

In this study, 316L stainless steel was used as workpiece material. The chemical composition of the alloy was determined as: the wt% is 0.02% C, the wt% is 16.64% Cr, the wt% is 10.35% Ni, the wt% is 2.03% Mo, and the rest is Fe. In the first step, a pre-machining operation was applied on a TOS TRENSIN machine to prepare the surface to be treated. Ball burnishing was then proceeded on the prepared surface with fixing the parameters regrouped in **Table 1**. The mentioned parameters were fixed after optimization of the process using the response surface "RSM" method based on BOX-Behnken design. The methodology of the optimization, as well as the


**Table 1.** *Burnishing parameters.*

**Figure 2.** *Altisurf500 profilometer (1); Innovatest microdurometer (2).*

analysis, were precisely described in our previous work [23]. After fixing the cited parameters, a number of passes (i) was varied by up to i = 5.
