XRD investigation of the Cu and Mn effects on the oxide scale of hot rolled AISI 304L stainless steel after annealing and shot-blasting

Abstract

Abstract The oxide scales of hot-rolled, annealed hot-rolled, and shot blasted annealed hot-rolled AISI 304L stainless steel with 0.2-0.4 wt.-%Cu and 1.0-1.7 wt.-%Mn were investigated by XRD. Mn but not Cu showed its effects on the oxide compounds. In the hot-rolled state, the oxide compounds consisted of Fe2O3 and Cr1.5Mn1.5O4 in all tested steels. Mn-rich (Fe,Mn)2SiO4 was found in the oxide of the tested steel with 1.2 wt.-%Mn while Mn3O4 was found in the oxide of the tested steel with 1.7 wt.-%Mn. The addition of Mn promoted the formations of Cr1.5Mn1.5O4, Mn-rich (Fe,Mn)2SiO4 and Mn3O4. The oxide compounds developed from Fe2O3 to (Fe0.6Cr0.4)2O3 or Cr1.3Fe0.7O3, Cr1.5Mn1.5O4 to CrMn2O4 and Mn-rich (Fe,Mn)2SiO4 to (Fe,Mn)2SiO4 after the annealing process. The shot blasting process of annealed hot-rolled 304L stainless steel descaled the outer oxides as (Fe0.6Cr0.4)2O3 and (Fe,Mn)2SiO4 and revealed the inner oxides Cr1.3Fe0.7O3, CrMn2O4 and Cr2O3. The results clearly showed that the fraction of CrMn2O4 increased according to the Mn content.