Abstract
The high-temperature oxidation behavior of selective laser melting (SLM) manufactured IN 625 was studied over 96 h of exposure at 900 °C and 1050 °C in air. An extensive analysis was performed to characterize the oxide scale formed and its evolution during the 96 h, including mass gain analysis, EDS, XRD, and morphological analysis of the oxide scale. The mass gain rate of the bare material increases rapidly during the first 8 h of temperature holding and diminishes at higher holding periods for both oxidation temperatures. High-temperature exposure for short periods (24 h) follows a parabolic law and promotes the precipitation of δ phase, Ni-rich intermetallics, and carbides. Within the first 24 h of exposure at 900 °C, a Cr2O3 and a (Ni, Fe)Cr2O4 spinel scale were formed, while at a higher temperature, a more complex oxide was registered, consisting of (Ni, Fe)Cr2O4, Cr2O3, and rutile-type oxides. Prolonged exposure of IN 625 at 900 °C induces the preservation of the Cr2O3 scale and the dissolution of carbides. Other phases and intermetallics, such as γ, δ phases, and MoNi4 are still present. The exposure for 96 h at 1050 °C led to the dissolution of all intermetallics, while the same complex oxide scale was formed.
Highlights
Nickel-based superalloys are metallic materials capable of withstanding high loading burdens during operation at high temperatures and in corrosive environments
The high-temperature oxidation behavior of selective laser melting (SLM)-manufactured IN 625 was studied over 96 h of exposure in air at 900 °C and 1050 °C, respectively
The high-temperature oxidation behavior of SLM-manufactured IN 625 was studied over 96 h of exposure in air at 900 ◦ C and 1050 ◦ C, respectively
Summary
Nickel-based superalloys are metallic materials capable of withstanding high loading burdens during operation at high temperatures and in corrosive environments. Based on experimental studies, it was ascertained that superalloys designed for maximum strength do not provide the maximum oxidation resistance, and vice versa [1,2]. IN 625 is a Ni-Cr superalloy developed in the 1950s as a substitute for stainless steel used in power plant components [3]. Even though it was developed 70 years ago, it is still known for its outstanding properties in oxidative and corrosive environments, with the high Cr content providing corrosion resistance while Mo and Nb ensure the strengthening of the face-centered cubic (FCC) structure γ phase [4,5]. The base material is protected by chromium oxide (Cr2 O3 ) or aluminum oxide (Al2 O3 ) scale formation [6,7,8,9,10,11,12], with Al being the most effective alloying element used to enhance oxidation resistance, and Cr being an element that reduces the oxidation rate of superalloys without W [6]
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