# Ultrasonic Surface Rolling Process: Properties, Characterization, and Applications
## 5 Applications and Recent Advances of USRP
The significant enhancement in surface mechanical properties and the presence of ultra-refined grains in the deformation layer is attributed to the effect of electropulsing. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{3}{*}{**Materials**} & \multirow{3}{*}{**Process**} & \multicolumn{2}{c}{**Roller material,**} & \multirow{3}{*}{**Frequency and**} & \multirow{3}{*}{**Observation**} \\  & & **Hardness and** & & & \\  & & **Diameter, Static Force** & & & \\  & & **or Pressure** & & & \\ \hline AISI 304 & \multirow{3}{*}{UNSM} & Unspecified; & 20 kHz; & Microhardness is increased by 50\% \\
[114] & & Unspecified; & 30 \(\upmu\)m & Surface roughness is reduced by 30\% \\  & & 2.38 mm; 40 N & RCS increased from \(-\)70 MPa to \(-\)1703 MPa \\  & & WC; & SPD layer of 32 \(\upmu\)m were observed \\
300M Steel & \multirow{3}{*}{UNSM} & Unspecified & 20 kHz; & Hardness enhancement is attributed to the refinement of lath martensite \\
[126] & & Unspecified; & 24 \(\upmu\)m & Wear rate is reduced by 39.7\% \\  & & 50 N & & Grain refinement by 25.8\% \\ AISI M4 high-speed & \multirow{3}{*}{UNSM} & Unspecified; & 30 kHz; & Microhardness increased by 24.1\% \\
[127] & & 2.38 mm; & 30 \(\upmu\)m & Surface roughness decreased by 88.3\% \\  & & 10N, 30 N, 50 N & & Wear rate reduced by 5.85 times \\ AA7075 Aluminum & \multirow{3}{*}{UNSM} & WC; & & Surface roughness reduced by 15.75\% \\ Alloy [99] & & Unspecified; & 20 kHz; & RCS increased by 78 times \\  & & 2.38 mm; 30 N & 30 \(\upmu\)m & Microhardness increased by 26\%. \\  & & WC; & & Wear Rate Reduced by: 2.75 times \\ AZ91D Magnesium & \multirow{3}{*}{UNSM} & Unspecified; & 25 kHz; & Microhardness increased by 28.3\% \\ Alloy [102] & & 2.38 mm; & 25 kHz; & CoF reduced by 23\%. \\  & & 10 N, 20 N, 30 N & 30 \(\upmu\)m & The wear rate is reduced by 30\%. \\  & & WC; & & Grain size is reduced to 39 nm. \\ Inconel 718 & \multirow{3}{*}{UNSM} & Unspecified; & 25 kHz; & Microhardness improved by 44\% \\
[89] & & Unspecified; & 25 kHz; & Fatigue life increased 5.25 times \\  & & 2.5 mm; & 40 \(\upmu\)m & Grain refined to 21.95 nm \\  & & 10 N, 50 N & & RCS of \(-\)1100 MPa observed on the surface \\ Cu-alloy [105] & \multirow{3}{*}{UNSM} & WC; & & Surface roughness Reduces by: 62.5\% \\
[105] & & Unspecified; & 20 kHz; & Nano hardness increased by 2.29 times. \\  & & 2.38 mm; 20 N & 30 \(\upmu\)m & Coefficient of friction reduced by 49.4\% \\ Ti64 & Laser- & WC; & & Microhardness improved by 75.2\% compared \\
[113] & & assisted & Unspecified; & 20 kHz; & to the as-received specimen \\  & & UNSM & 2.38 mm; 50 N & 24 \(\upmu\)m & Nanocomposite microstructure observed with nanoscale precipitates \\ AISI 304 SS & \multirow{3}{*}{EP-USRP} & Unspecified; & 30 kHz; & Residual stress improved by 4.8 times \\
[123] & & 14 mm & 8 \(\upmu\)m & Surface roughness reduced by 20\% \\  & & & & Improved surface hardness by 119.5\% for \\
304 Austentic SS & \multirow{3}{*}{EP-USRP} & Unspecified; & & EP-USRP, and 102.6\% for USRP \\
[115] & & 80 HRC; & 30 kHz; & Surface roughness reduced by 83.3\% for \\
[115] & & 14 mm; 700 N & 8 \(\upmu\)m & With the increase in current density, surface roughness slightly reduces for EP-USRP \\  & & & Improved surface hardness up to 28.3\% for \\  & & & EP-USRP, and 41\% for USRP \\ Ti6 Al4V & \multirow{3}{*}{EP-USRP} & Unspecified; & 30 kHz; & Increase in residual stress by 12.8 times in \\
[125] & & 14 mm; 1500 N & 8 \(\upmu\)m & USRP and 15.6 times in EP-USRP \\  & & & Surface roughness reduced by 84.6\% in \\ CrMnFeCoNi High & \multirow{3}{*}{EP-USRP} & Cemented carbide; & & Tensile strength is improved by 3\% by \\ entropy alloy [128] & & unspecified; & 30 kHz; & EP-USRP and 8.7\% by USRP. \\  & & 14 mm; & 6 \(\upmu\)m & Observed 21.9\% elongation in EP-USRP and 14.9\% in USRP. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Recent advancement of USRP. To enhance the benefits obtained from USRP, scholars used combination techniques.