Fe24Mn4Al5Cr合金高温氧化诱发贫Mn层的耐蚀性

Corrosion Resistance of Oxidation-Induced Mn Depletion Layer on Austenitic Fe24Mn4Al5Cr Alloy

摘要:

研究了Fe24Mn4Al5Cr合金在800和950 ℃空气中的循环氧化动力学及氧化层形貌、成分和组织结构。由于Mn元素的选择性氧化，在氧化层与基体之间形成高耐蚀性的贫Mn铁素体层。对贫Mn铁素体层的耐腐蚀性能进行了分析。结果表明，950 ℃氧化10 h后，氧化层与基体间形成形状弯曲、厚度约6 μm、较基体贫Mn (5 at%)、富Fe (85 at%)的铁素体层。降低氧化温度至800 ℃、延长氧化时间至160 h，氧化层与基体之间形成连续平整、厚度约9 μm的贫Mn (6 at%~19 at%)、富Fe (83 at%~72 at%)和富Cr (8 at%)的铁素体层。在1 mol/L Na2SO4溶液中于800 ℃氧化160 h后的铁素体贫Mn层的阳极极化曲线呈自钝化，自腐蚀电位Ecorr由原始合金的–710 mV提高至57 mV，维钝电流密度ip从3.3 μA/cm2下降至0.7 μA/cm2，耐蚀性能提高

Abstract:

The oxidation kinetics of austenitic Fe24Mn4Al5Cr alloy oxidized at 800 °C for 160 h and 950 °C for 10 h in air, and the surface morphology, composition and the microstructure of the oxide scales were investigated in order to improve the corrosion resistance. An oxidation-induced Mn depletion layer between the alloy matrix and the oxide scales formed at the two oxidation temperatures by the selective oxidation of Mn. The results show that after oxidation at 800 °C for 160 h, the continueous and smooth ferrite layer about 9 μm thick near the scale-metal interface has an enrichment of Fe content of 83 at%~72 at% and Cr content of 8 at%, and a depletion Mn of 6 at%~19 at%. However, at 950 °C for 10 h, the ferrite layer about 6 μm thick is in curved shape with the enrichment in Fe of 85at% and the depletion in Mn of 5at%. The anodic polarization curves of the Mn depletion layer at 800 °C for 160 h in 1 mol·L-1 Na2SO4 solution has a self-passivation, with the higher corrosion potential of 57 mV(SCE) and the lower passive current density of 0.7 μA/cm2, compared with –710 mV(SCE) and 3.3 μA/cm2 for Fe24Mn4Al5Cr austenitic alloy. Therefore, the corrosion resistance of the oxidation-induced Mn depletion layer on Fe24Mn4Al5Cr alloy increases