Effect of Applied of Pre-Stresses on Corrosion Behavior of 304 Stainless Steel in 1N H2SO4

Abstract

This research is devoted to study the effect of applying different pre-tensile stresses (255,305,355,405,455,505 555 and 605) MPa on the microstructure, hardness and corrosion behavior of 304 stainless steel in 1N H 2 SO 4 . The stress-strain curve was drawn for standard (304) stainless steel in laboratory environment. The curve was divided into three zones. At zone one the values of elastic pre-stresses vary between (σ 0 -σ pro. ) MPa. The results showed; that the corrosion rate was very little increased compared with that of as received (304) stainless steel. The microstructure presented undeformed austenitic grains and the hardness value was (157.433) Hv. At zone two the value of plastic pre-stress varies between (σ pro .-σ U.T.S ) MPa. The corrosion rate increases after applying pre-stress between (σ 255 -σ 455 ) MPa. The microstructure showed that the austenitic grains begin to deform in the direction of applied prestresses. The maximum hardness at this region was (229.2) Hv, but at higher pre-stress (σ 455 -σ 605 ) MPa, the corrosion rate decreases. The microstructure inspection shows the deformed austenitic grain and ά-martensitic phase needle are appeared inside austenitic grains and the hardness reached the maximum value (332.433) Hv. At zone three the values of pre-stresses are between (σ 605 -σf) MPa. The results showed that the corrosion rate increases. The investigation of microstructure showed that there are distortion in austenitic grains and ά-martensite phase observed inside austenitic grains. The hardness reached the maximum value at (354.3) Hv. The necking of gauge length of specimens occurs in specimens and this leads to deterioration in original properties