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

Xiaolei Han,Changji Li,Chunhuan Chen,Hongwang Zhang,Xiaodan Zhang

doi:10.3390/nano11071769

Abstract

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

Highlights

Gradient nanostructure (GNS), i.e., a nanostructure with continuously varied characteristic size within certain length scale, exhibits deformation behaviors and mechanical properties that are different from but usually superior to those of nanostructures with relatively uniform size distribution [1,2]
Deformation-induced nanostructuring lies in the refinement of the coarse-grains down to nanometer-scale via applying severe plastic deformation, and the existing techniques have been developed with the aim to produce deformation as heavy as possible
We demonstrated that an ultrahigh frequency surface processing with linecontact roller ultrasonic rolling treatment (USRT) is able to fabricate GNS with reasonable thickness and good surface quality

Summary

Introduction

GNS, i.e., a nanostructure with continuously varied characteristic size within certain length scale, exhibits deformation behaviors and mechanical properties that are different from but usually superior to those of nanostructures with relatively uniform size distribution [1,2]. Various techniques have been developed to fabricate. GNS, among which surface gradient plastic deformation has drawn great attention due to its wide applicability, high efficiency, low cost, and more importantly its lack of introducing artificial defects and contaminations. Deformation-induced nanostructuring lies in the refinement of the coarse-grains down to nanometer-scale via applying severe plastic deformation, and the existing techniques have been developed with the aim to produce deformation as heavy as possible. High stress generated due to small contact area enables the activating high density of crystal defects to refine the coarse grains down to Nanomaterials 2021, 11, 1769. It is disadvantageous to the surface quality, which is very important for higher service reliability and longer service life

Methods

Results

Discussion

Conclusion