Combined fabricating method for gradient nanostructure in surface layer of metal workpiece

A combined fabricating method for a gradient nanostructure in a surface of a metal workpiece, the method comprising:

• performing a laser shock peening (LSP) treatment on the surface of the metal workpiece to induce a plastic deformation layer on the surface of the metal workpiece;
• after performing the LSP treatment, then performing a surface mechanical attrition treatment (SMAT) on the surface of the metal workpiece to nanocrystallize the surface of the metal workpiece;
• and
• after performing the SMAT, finally obtaining the gradient nanostructure in the surface of the metal workpiece with a desirable layer thickness and an optimized micro-structure distribution,
• wherein the method further comprises:
• (1) prior to performing the LSP treatment, burnishing, polishing, and performing a first cleaning of the surface of the metal workpiece;
• (2) prior to performing the LSP treatment, determining a pulse width, a pulse energy, a frequency, a spot diameter, and a number of coverage layers of LSP related with a material of the metal workpiece, and attaching an absorption layer to the surface of the metal workpiece, wherein the performing of the LSP treatment comprises performing a massive overlapped LSP treatment on areas of the surface of the metal workpiece;
• (3) removing the absorption layer on the surface of the metal workpiece after the areas of the surface of the metal workpiece are treated by massive overlapped LSP, and performing a second cleaning of the surface of the metal workpiece;
• and
• (4) determining a vibration frequency, a ball diameter, and a treatment time of SMAT related with the material of the metal workpiece, wherein the SMAT on the surface of the metal workpiece is performed based on the vibration frequency, the ball diameter, and the treatment time of SMAT related with the material of the metal workpiece.