The Microstructural Evolution of Haynes 282 Alloy During Long-Term Exposure Tests

Abstract

Haynes 282 alloy is a γ′ precipitation strengthened nickel based superalloy designed by Haynes International Incorporation in 2005. This alloy is currently being evaluated for use as high temperature components at 700°C Advanced-Ultra Supercritical (A-USC)power plants, thus it is particularly important to have good creep property and microstructure stability.

In this study, calculations by software Thermal-Clac and long-term high temperature (up to 10,000 hours and 800°C) exposure tests were carried out on the Haynes 282 alloy. The microstructural evolution in the samples of alloy Haynes 282 during long-term exposure tests at 700°C, 760°C, 800°C was characterized by scanning electron microscopy, Energy Dispersive Spectrometer and transmission electron microscopy. The aim of this study is to develop and gather the necessary data in order to determine the utility of this alloy for various applications in A-USC power plants. The calculation results show that the equilibrium phases of the alloy 282 in the possible operating temperature range of 700~800 °C include γ, γ′, μ, M₆C and M₂₃C₆, and trace phases MC and M₃B₂. The microstructural observations show that there is no deleterious phases in samples at 700°C even exposured for 10,000 hours. However, when the temperature rises to 760 °C or 800 °C, blocky Titanium-rich carbides and bar-like or acicular Molybdenum-rich μ phase were observed in samples exposured for more than 3,000 hours.