The High-Temperature Corrosion Behavior of Fe-28Al Base Alloys Containing the Third Elements in H2/H2S/H2O mixed gases

• Main Authors: Tung Lin Chiang, 姜東林
• Other Authors: Wu Kai
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/19801579003657934222

碩士 === 國立海洋大學 === 材料工程研究所 === 87 === The high-temperature corrosion of Fe-Al base ternary alloys with additions of Cr, Mo, Nb, or Y (containing various amounts of 0.5, 2, 5, or 10 at.%) has been studied over the temperature range of 700~900℃ in the H2/H2S/H2O mixed gases. The results indicated that the corrosion kinetics of all alloys studied followed a parabolic law with two-stage kinetics at 900℃ in all cases. The duration of an incubation period increased with increasing amounts of the third alloying elements. X-ray diffraction results showed that α-Al2O3 is the major scale formed on the surface of the alloys. Other scales formed are strongly dependent on the third alloying elements. By forming adequate amounts of Nb3S4 on the surface, the outward diffusion of Fe and Al cations can be reduced, resulting in slow corrosion rates for Fe-28Al-xNb alloys. In addition, the formation of Y2O3 enhanced the adherence between the scales and the substrate, resulting in a significant reduction in the corrosion rates for Fe-28Al-xY alloys. Moreover, the corrosion rates of Fe-28Al were also significantly reduced by adding 5 at.% of Mo or Cr. However, both Fe-28Al-10Cr and Fe-28Al-10Mo alloys revealed a poor corrosion resistance as compared to those of Fe-28Al-5Cr and Fe-28Al-5Mo. The main reason for the deterioration effect of the Fe-28Al-10Cr and Fe-28Al-10Mo is due mainly to the fast formation of FeCr2S4 and FeMo2S4 ternary sulfides, which provided an easy path for Fe outward diffusion, leading to high corrosion rates. Based on the kinetics results, Fe-28Al-10Y is the best corrosion-resistant alloy in the present study.