镍基铸造高温合金K35的热腐蚀行为

HOT CORROSION OF NICKEL-BASE CAST SUPERALLOY K35 AT 800℃

研究了涂有75%Na2SO4+25%NaCl盐膜的镍基铸造高温合金K35在800℃～900℃的热腐蚀行为.结果表明,该合金在实验条件下发生高温热腐蚀.在800℃,腐蚀动力学曲线大体遵循抛物线规律.腐蚀产物分为3个区域:即外层是以Cr2O3为主相对致密的具有保护性的氧化层,中间层是富Ti层,内层是以Al、Ti为主的氧化物.腐蚀形貌观察说明,热腐蚀的发展主要伴随着致密氧化层的增厚以及Cr2O3保护性氧化膜的挥发,且涂盐导致Cr2O3挥发温度降低.在800℃及850℃表面有少量硫化物形成,随腐蚀温度增高有内硫化物产生.腐蚀动力学和腐蚀形貌特点支持热腐蚀的硫化-碱融机理模型.

Hot corrosion behavior of nickel-base cast superalloy K35 in the presence of a thin film of 75 %Na2SO4＋25 % NaCl in air at 800℃- 900℃ was studied. The results showed that the superalloy was subjected to “high temperature” hot corrosion attack under the experimental condition. The kinetics curve of hot corrosion followed basically the parabolic law. Corroded products can be divided into three layers, which external scales of Cr2O3 formed mainly, intermediate layer was Ti-rich, internal layer was mainly oxides of A1. For the corrosion process, especially in the steady state, the development of hot corrosion was characterized by the rapid growth of the compact oxide layer and was accompanied by some volatility of Cr2O3, which volatile temperature is decreased by coating the film of salt on the specimens. There are a little sulfides on the surface of the specimens at 800℃ and 850℃. With increasing temperature internal sulfides were formed. The corrosion kinetics and morphology examinations tend to support the sulphidization-basic dissolution model previously proposed for hot corrosion mechanism.