Corrosion Behavior of Fe(Ni)CrAlX Alloys in an HCl-H_2O-H_2 Gas Mixture at 800℃

摘要

The high-temperature-corrosion behavior of a series of Fe(Ni)CrAlX-typc alloys (where X = Zr and Hf, e.g.) has been studied in a gas mixture of 50% HCl-10% H_2O-H_2 at 800℃. The experimental results obtained indicated that Ni-base alloys had superior corrosion resistance to Fe-base alloys in this gas mixture. While the exposed Ni-base alloys showed weight gains due to the formation of oxides (e.g., Al_2O_3, Cr_2O_3) as well as CrCl_2, the Fe-base alloys exhibited substantial weight losses resulting from the formation and subsequent evaporation of FeCl_2. This study also demonstrated that Fe(Ni)Cr8AlX-type alloys, which contained high aluminum, had better chloridation resistance than Fe(Ni)25CrAlX-type alloys, which had high chromium. The improved performance of Fe(Ni)Cr8AlX-type alloys was due to the presence of a high level of aluminum which promoted the formation of protective Al_2O_3. Although the presence of chromium in the alloys promoted the formation of Cr_2O_3, the high level of chromium adversely affected the chloridation resistance of Fe(Ni)25CrAlX-type alloys, due to the development of chloride (CrCl_2) at the interface of the oxide scale and alloy substrate.