Effects of Different Grit Blasting Environments on the Prepared Steel Surface

Abstract

This study examines the effect of grit blasting on the surface and subsurface characteristics of low-carbon steel substrates under dry and wet environments. Three types of wet environments have been simulated: tap water, saline water, and ethyl alcohol. The variation in average surface roughness with grit size, standoff distance (SOD), and blasting time has been analyzed under all conditions. A mathematical model has been developed to estimate the increment in the contact area of each rough surface created by grit blasting. The optimal sets of process parameters for each environment have been suggested based on the maximum increment. The optimal conditions have been found to shift toward higher SODs and time periods under wet conditions. Vickers microhardness testing has been undertaken to study the hardness of the subsurface zone of the grit-blasted samples. Work hardening of the subsurface regions is higher under dry conditions compared to the same in wet conditions. The depth of the affected layer is higher in case of higher surface hardening. X-Ray Diffraction analysis has been carried out to identify the phases formed on the as-blasted substrate surfaces. Nascent surface metallurgy remains unchanged under dry and wet conditions, except in saline water environments where significant contamination has been observed. Subsurface microstructures of the blasted substrates have been studied using Field Emission Scanning Electron Microscopy and Energy Dispersive Spectroscopy. Subsurface damage is substantial under dry conditions. The deformation effect and formation of subsurface cracks are found to be localized in the vicinity of the grit-blasted surfaces. Among all the blasting environments, the alcohol medium offered reasonably high roughness with minimum hardening effect on the substrate. © 2023, ASM International.