Laser shock peening wavelength conditions for enhancing corrosion behaviour of titanium alloy in chloride environment

Abstract

The present study has been carried out to analyse the effect of the laser shock peening (LSP) with the absence of a coating on titanium alloy (Grade 5—Ti6Al4V) and to establish the best set of LSP parameters for enhanced surface characteristics. Ti6Al4V which has excellent mechanical properties is penned using Nd:YAG pulsed laser with 2D XY translation with water as confinement medium. Power density (3, 6, 9 GW/cm2), wavelength (532, 1064 nm) and overlap (60%, 70%) are the three process parameters considered to perform laser shock peening without coating (LSPwC). Surface roughness is increased with raise in wavelength and as well as other parameters too. Even though hardness is increased in both wavelengths, enhanced hardness is caused with 1064 nm wavelength. An adequate amount of compressive stress is induced with 3 GW/cm2 at 50 μm depth. The rate of corrosion is dropped in samples LSPwC with 532 nm compared with 1064 nm wavelength due to its low surface roughness and surface oxide layer which holds the fluctuation of current density with respect to potential. SEM observation showed pits on the surface of samples peened with a 1064 nm wavelength. And this surface pitting is correlated with the fall of charge transfer resistance in such samples.