Fabrication of Low Roughness Gradient Nanostructured Inner Surface on an AISI 304 Stainless Steel Pipe via Ultra-Sonic Rolling Treatment (USRT)

Gradient nanostructure (GNS) has drawn great attention, owing to the unique deformation and properties that are superior with uniform scale. GNS is commonly fabricated via surface plastic small tips (of balls or shots) so as produce high refine coarse grains, but unfortunately it suffers from deterioration of quality which hard guarantee reliable service. Although there mirror-finishing techniques can greatly enhance quality, induced slight unable reasonable thickness. Here, we propose a method fabricate layer substantially enhanced ultra-sonic rolling treatment (USRT), namely, roller vibrated at frequency 20,000 Hz. It found 4-pass USRT able 20–30 µm thick on AISI 304 stainless steel pipe inner surface, wherein by one order magnitude starting Ra = 3.92 0.19 µm. Processing high-frequency vibration necessary for both good effective accumulation heavy surface. The flattening mechanism well microstructural evolution millimeter- nanometer-scale discussed.