Thermal Stability of a New Ni–Fe–Cr Base Alloy with Different Ti/Al Ratios. Issue 2 (February 2015)

• Record Type: Journal Article
• Authors: Wang, Changshuai; Wang, Tingting; Tan, Meilin; Guo, Yongan; Guo, Jianting; Zhou, Lanzhang
• Is Part Of: Journal of materials science & technology. Volume 31:Issue 2(2015:Feb.)
• Page Start: 135
• Page End: 142
• Publication Date: 2015-02
• Subjects: 700 °C A-USC -- Ni–Fe–Cr base alloy -- Thermal stability -- η phase -- Ti/Al ratio; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2014.07.008
• Languages: English
• ISSNs: 1005-0302

Abstract

Abstract : Influence of Ti/Al ratios on the thermal stability of a new low cost Ni–Fe–Cr base wrought alloy, designed for application at 700 °C in advanced ultra-supercritical coal-fired power plants (700 °C A-USC), was investigated both experimentally and thermodynamically. After standard heat treatment, the alloys with different Ti/Al ratios had the same microstructural characteristics. However, compared with the alloys with high Ti/Al ratio, the low Ti/Al ratio can increase the γ′-solvus temperature, decrease γ′ coarsening rate and reduce the temperature range of η phase precipitation. For the alloys with low Ti/Al ratio, the yield strength has no obvious decrease during long-term thermal exposure at 700 and 750 °C, but after thermal exposure at 750 °C for 5000 h, the yield strength of the alloys with high Ti/Al ratio obviously decreases due to the η phase precipitation. The influence of η phase on mechanical properties is related with its size. When the η phase is small, it has no obvious influence on mechanical properties, but η phase becomes the crack initiation site with the further growth of η phase. It can be concluded that the decrease in Ti/Al ratio can improve the thermal stability to meet the requirement of 700 °C A-USC coal-fired power plants.