Experimental TTT diagram of HAYNES 282 alloy

Abstract

HAYNES® 282® alloy was developed by Haynes International as an age-hardenable, yet fabricable, wrought Ni-base superalloy. To date, the alloy has been specified for a number of applications, most notably in the hot sections of both aero- and industrial gas turbines. A Time-Temperature-Transformation (TTT) diagram is a useful guide to assess an alloy’s behavior during thermo-mechanical processing and heat treating. Starting with the (commercially relevant) 1149 °C (2100 °F) mill-annealed condition, a time (0.1–100 h)—temperature (649–1121 °C (1200–2050 °F)) exposure matrix was executed. Precipitates, which had formed as a result of these exposures, were analyzed by light microscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and, in selected cases, by x-ray diffraction (XRD). Chiefly, γ′ and two types of carbides, Cr-rich M23C6 and Mo-rich M6C, were found. Approximate C-curves for these phases were constructed, and some implications for the alloy’s processing and properties characteristics are discussed.