Studies on ultra-short pulsed laser shock peening of stainless-steel in different confinement media

TL;DR

This study investigates how ultra-short ps laser pulses in different liquids affect the surface hardening of stainless steel through laser shock peening, revealing the influence of confinement media on hardness enhancement.

Contribution

It demonstrates the effects of liquid confinement media on laser shock peening of stainless steel using ps pulses, highlighting the role of acoustic impedance in surface hardness increase.

Findings

Hardness increase depends on the confinement medium's acoustic impedance.

Ps laser pulses cause less plasma breakdown than shorter pulses.

Surface hardness enhancement is significant and medium-dependent.

Abstract

Laser Shock Peening (LSP) of stainless-steel 316 and 316L was studied using Ti: Sapphire laser pulses of about 2 ps duration, maximum energy of about 1mJ and pulse repetition rate of 5kHz in different liquid confinement media of Ethanol, Deionized water and separate aqueous solutions of NaCl and Glycerol. It is found that the laser fluence and/or energy attenuating mechanisms like self-focusing, filamentation, plasma breakdown in the confinement media are less significant with ps laser pulses than those with sub-ps or fs pulse durations. It is shown that the resulting surface hardness of the peened steel as a function of laser fluence depends significantly on the confinement media and the relative increase in the hardness increases monotonically with the acoustic impedance of the liquid of the confinement medium used during LSP.