Effect of Laser Shock Peening on HSLA Steel Subjected to Harsh Corrosive Environment

Abstract

HSLA steels are often used in the construction of underwater tunnels, offshore platforms, and other structural components due to their better formability, weldability, and reasonably well corrosion resistance. However, in extreme and harsh conditions corrosion resistance of HSLA steel may degrade drastically which forces the concerned industries/researchers to take some precautionary measures by means of improving the surface attributes. Since heavy component replacement is a significant problem in the automotive and marine fields, surface property enhancement of components is a superior alternative. Many surface treatment methods may be employed to safeguard the components before being made into an application that includes traditional shot peening (SP), ball burnishing, nitriding, and carburizing. In shot peening, it is aimed to produce some compressive residual stress (CRS) at the surface to improve the corrosion resistance. But, SP introduces a poor surface finish and in association, less compressive residual stress. Laser shock peening (LSP), is one of the most promising methods of surface modification that have the least unfavorable effect on the surface. Although different approaches were taken to improve the properties of HSLA steel, considerable research studies were not carried out to examine the surface treatment by LSP of HSLA steel. This research examines the impact of laser shock peening on the electrochemical performance of ASTM A 588 Grade D HSLA steel in a 3.5 Wt.% NaCl solution. The development of the microstructure, micro-texture, surface roughness, residual stress, microhardness, dislocation density, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) are thoroughly investigated. The LSP-induced gradient compressive residual stress along with strong {011} <111> texture component development and marginally refined microstructure improved the corrosion resistance. The EDS and Raman spectroscopy results also demonstrated the persistence of a compact and continuous passive oxide film/layer, primarily made of Fe2O3, on the surface of the laser-peened specimens