Performance of shot peened surfaces subject to crystallization fouling

Shot peening is frequently used in industry to primarily improve surface properties in term of material fatigue and corrosion. It is nevertheless questionable whether such shot peened surfaces would simultaneously withstand fouling conditions. The present study endeavours to put this question into perspective. Two different shot peened surfaces with intensities of 4N and 6N were investigated in which the stainless steel surfaces AISI 304 BA was used as baseline substrate. The surface characterizations showed that shot peening increased the surface roughness up to 7-fold compared with the untreated stainless steel surface. The degree of wettability in terms of water contact angle was also reduced up to 28.3% in comparison to the untreated surface. The shot peened surfaces were then subjected to the deposition of CaSO₄ during convective heat transfer. Compared to the untreated stainless steel surface, the induction period reduced by more than 30% along with increased initial fouling rate by more than 2-fold. The overall heat transfer coefficient also decreased up to 65%. In addition, visual observations confirmed that the deposit layer on the shot peened surfaces was thicker, more adhesive, rough and less porous than the one that was formed on untreated stainless steel surface.