碱金属硫酸盐沉积引起的铁基合金在中温下的热腐蚀

研究工业纯铁、Fe-Cr和Fe-Al合金有表面Na_2SO_4或Na_2SO_4-K_2SO_4沉积物时在含SO_3的富氧气氛中于中等温度区间的热腐蚀行为。研究结果表明,铁基合金在实验条件下发生的热腐蚀是由液态Na_2SO_4—Fe_2(SO_4)_3或Na_2SO_4-K_2SO_4-Fe_2(SO_4)_3共晶所致,其腐蚀行为与温度、气体组成、合金元素含量、沉积物组成有关。腐蚀形貌的观察表明,铁基合金热腐蚀的发展伴随着疏松的Fe_2O_3层的增厚和紧靠合金表面相对致密的氧化层的快速成长。在合金/氧化物

ALKALI SULFATE DEPOSITS INDUCED HOT CORROSION OF IRON BASED ALLOYS AT INTERMEDIATE TEMPERATURES

Hot corrosion behavior of commercial iron, Fe-Cr and Fe-Al alloys in the presence of either a Na_2SO_4 or Na_2SO_4-K_2SO_4 deposit on their surfaces in oxygen-rich atmospheres containing SO_3at intermediate temperatures was studied. The results showed that the hot corrosion of iron based alloys occurring in the experimental conditions was caused by liquid sulfate eutectics of Na_2SO_4-Fe_2(SO_4)_3 or Na_2SO_4-K_2SO_4-Fe_2(SO_4)_3. The corrosion behavior of the materials was dependent upon temperature, gas composition, alloying element content and deposit component. The examinations of corrosion morphology indicated that the proceeding of hot corrosion was accompanied by the increase in thickness of a porous Fe_2O_3oxide layer and the rapid growth of a comparetively compact oxide layer right on the metal surface. In addition, sulfides were observed at the metal / oxide interface as well as in the compact oxide layer. On the basis of experimental results, an electrochemical mechanism is proposed to illustrate hot corrosion processes of iron based alloys at intermediate temperatures. The effects of temperature, gas composition, alloying element content and deposit component on corrosion behavior are also discussed.