Fine Precipitates in Nickel Base Superalloys

Abstract

Presence of fine, secondary/tertiary precipitates in superalloys improves especially the creep-fatigue properties of these alloys. It is conveniently accepted that the fine precipitates form non-isothermally, for example, during cooling from an aging temperature or isothermally during a secondary, lower temperature aging. In the current study, several single-aging treatments were conducted to assess the formation of the fine precipitates in the polycrystalline, nickel-base superalloy IN738LC. The agings were carried out stress-free at 950 o C, 1050 o C, 1120 o C, and 1140 o C for various times. Stressed agings at 950 o C and 1050 o C were also conducted. A time-dependent isothermal formation of the fine precipitates was observed. The formation time decreased as the aging temperature increased. It is suggested that dissolution of some coarse precipitates, evolution of the precipitate-matrix interface toward a fully faceted one, and increased matrix channel width saturate the channels and control the formation of the fine precipitates.

Oxidation Behavior at 1000 °C of Low-Mn High-Cr Cantor’s HEA-Based Alloys Strengthened or Not by MC Carbides

“…Superalloys, the metallic alloys with outstanding high-temperature properties in the fields of mechanical behavior and corrosion resistance [1][2][3][4], are most often based on nickel [5][6][7] and cobalt [8][9][10], which are more and more considered to be critical [11][12][13]. The recent appearance of high-entropy compositions allows for the expectation of the moderate replacement of Ni and Co with cheaper and more abundant elements without dramatic losses of properties and even, contrarily, with a possible increase in these properties.…”