## 4 Conclusions  
In conclusion, this study has demonstrated the significant impact of ball burnishing parameters on the surface quality of Ti grade 2 under both dry and MQL conditions. The research highlights the superior performance of MQL conditions, which consistently produce better surface finishes than dry processing. This is attributed to the enhanced lubrication and cooling effects provided by MQL, which facilitate more effective plastic deformation of the surface layers.  
The optimal surface quality was achieved with a burnishing force of 200 N, a feed rate of 0.5 mm/min, and four passes under MQL conditions, resulting in the lowest surface roughness (Ra = 0.306 \(\upmu\)m). The results of the ANOVA on the statistical analysis showed that the processing environment had the greatest influence on the total variance with 50.93%. The number of passes and burnishing force were also statistically significant, showing the effect of these parameters on the required surface properties.  
The regression model developed in this study provides a robust predictive tool for surface roughness, with an R-squared value of 87.66%. It offers valuable guidance for optimizing ball burnishing processes in industrial applications. These findings contribute to a deeper understanding of the process parameters' effects on Ti grade 2, supporting the development of more efficient and environmentally conscious manufacturing processes.  
Future research could consider additional parameters such as ball diameter and burnishing speed, as well as their effects on other surface integrity characteristics, to further enhance the applicability of ball burnishing in various industrial sectors.  
The results of this study contribute significantly to the understanding of ball burnishing processes for Ti grade 2 and provide valuable insights for industrial applications. MQL-assisted ball burnishing was found to be an environmentally friendly and effective method of improving the surface quality of Ti grade 2. This property makes it particularly suitable for aerospace and biomedical applications where surface quality is critical. Future research should investigate additional parameters such as ball diameter and burnishing speed and their effect on other surface integrity characteristics.  
Conceptualization, S.C.C. and K.L.; methodology, S.C.C. and K.L.; validation, S.C.C. and K.L.; formal analysis, S.C.C. and K.L.; investigation, S.C.C. and K.L.; data curation, S.C.C. and K.L.; writing--original draft preparation, S.C.C. and K.L.; writing--review and editing, S.C.C.  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Parameters** & **Degrees of Freedom** & **Sum of Squares** & **Mean Squares** & **F-Value** & \(p\)**-Value** \\ \hline Environment & 1 & 0.105494 & 0.105494 & 41.29 & 0.000 \\ \hline Force (N) & 2 & 0.020652 & 0.010326 & 4.04 & 0.052 \\ \hline Feed rate & & & & \\ (mm/min) & 2 & 0.005955 & 0.002978 & 1.17 & 0.351 \\ \hline Passes & 2 & 0.049448 & 0.024724 & 9.68 & 0.005 \\ \hline Error & 10 & 0.025551 & 0.002555 &.. &.. \\ \hline Total & 17 & 0.207100 &.. &.. &.. \\ \hline \hline \end{tabular}
\end{table}
Table 3: Details of ANOVA results of surface roughness for the S/N ratio.  
and K.L.; visualization, S.C.C. and K.L. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data are contained within the article.  
The authors declare no conflicts of interest.