Comparative study of the reactive elements effects on oxidation behavior of a Ni-based superalloy. (September 2021)

• Record Type: Journal Article
• Authors: Rehman, Khalil; Sheng, Naicheng; Sang, Zhiru; Xun, Shuling; Wang, Zhenjiang; Xie, Jun; Hou, Guichen; Zhou, Yizhou; Sun, Xiaofeng
• Is Part Of: Vacuum. Volume 191(2021)
• Publication Date: 2021-09
• Subjects: Superalloys -- High temperature oxidation -- Reactive elements -- Microstructure -- Scale adhesion; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2021.110382
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: Hf, Y, and Ce (0.1 wt % each) were added in Ni-based superalloy, prepared by vacuum induction melting (VIM), and their effects on oxidation behavior were investigated after 300 h, over the temperature range 900–1100 °C. The surface of the oxide layer predominantly consisted of Al2 O3 and NiO at 900 ° C. At 1000 ° C, most of the surface is covered by Al2 O3 along with a small amount of NiAl2 O4 . However, at 1100 ° C, the oxide layer's surface mainly formed of NiAl2 O4 with plate-like α-Al2 O3 . It has been found that Hf produced excellent oxidation resistance and improved the scale adhesion to the alloy surface. On the other hand, Ce has a limited effect at high temperatures, and the scale adhesion is decreased with increasing oxidation time. From the analysis of oxidation kinetics and microstructure, it has been proposed that the dynamic segregation of reactive elements does not physically leads to the blocking of ions outward diffusion through Al2 O3 . The improvement in oxidation resistance of alumina forming alloys produced by reactive elements is explained based on ionic radii, chemical reactivity with alloying elements, and alteration in the alumina grain boundary's electronic properties. Highlights: Ni-based superalloys added with Hf, Y, and Ce are prepared by vacuum induction melting. Reactive elements significantly improved the oxidation resistance of superalloys. The oxide scale consists of three layers having sequence Al2 O3 /mix oxides/Al2 O3, NiAl2 O4 . Hf is comparably more effective in improving the oxidation resistance of superalloy. Ce has a limited blocking effect and has a greater growth rate.