High-Temperature Oxidation Kinetics and Scales Formed on P122 Steel Welds in Air

摘要

P122 steel, with a composition of Fe-10.57%Cr-1.79%W-0.96Cu-0.59Mn was arc-welded and oxidized between 600℃ and 800℃ in air for up to 6 months. The oxidation rates increased in the order of the base metal, weld metal, and heat-affected zone (HAZ), depending on the microstructure. The scale morphologies of the base metal, weld metal, and HAZ were similar because it was determined mainly by the alloy chemistry. The scale consisted primarily of a thin Fe_2O_3 layer at 600℃ and 700℃ and an outer Fe_2O_3 layer and an inner (Fe_2O_3, FeCr_2O_4)-mixed layer at 800℃. The microstructural changes resulting from heating between 600℃ and 800℃ coarsened the carbide precipitates, secondary Laves phases, and subgrain boundaries in the matrix, resulting in softening of the base metal, weld metal, and HAZ.