High‐Temperature Creep Properties of an Additively Manufactured Y2O3 Oxide Dispersion‐Strengthened Ni–Cr–Al–Ti γ/γ' Superalloy. Issue 12 (9th August 2022)

• Record Type: Journal Article
• Authors: Kenel, Christoph; De Luca, Anthony; Leinenbach, Christian; Dunand, David C.
• Is Part Of: Advanced engineering materials. Volume 24:Issue 12(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-09
• Subjects: additive manufacturing -- creep -- laser powder bed fusion -- nickel superalloy -- oxide dispersion strengthening; Materials -- Periodicals; 620.11
• DOI: 10.1002/adem.202200753
• Languages: English
• ISSNs: 1438-1656

Abstract

Abstract : The effects of the modification of a high‐γ' Ni–8.5Cr–5.5Al–1Ti (wt%) model superalloy with 0.5 wt% Y2 O3, manufactured by laser powder bed fusion, on the microstructure and compressive creep resistance, are investigated. Compared with the base alloy, the oxide dispersion‐strengthened (ODS) alloy exhibits 8–10 times slower creep rates at 800 °C, over a wide range of compressive stresses (35–250 MPa). Two creep regimes are observed: diffusional creep, hypothesized to be due to grain boundary sliding, and dislocation creep, with stress exponents n of 2 and 5, respectively. Compared with the horizontal direction, the vertical build direction is characterized by lower creep rates, due to the vertically elongated grain structure. Nonetheless, the ODS alloy's weakest (horizontal) direction shows better creep resistance than the non‐ODS alloy in its strongest (vertical) direction, despite a higher number of as‐built defects (slag, cracks) in the ODS alloy. The strengthening potential of ODS modification of additively manufactured nickel‐based superalloys is thus demonstrated. The development of successful commercial ODS nickel superalloys for additive manufacturing processing requires further additions of grain boundary strengthening elements as the dispersoids do not significantly increase the grain boundary strength, as their cracking is prevalent in the ODS alloy. Abstract : Additive manufacturing allows to create parts made of materials hard to produce by conventional methods, such as oxide dispersion‐strengthened (ODS) nickel‐based alloys. Herein, the added Y2 O3 dispersoids provide a noticeable increase in mechanical properties at high temperatures, of a γ'‐strengthened model nickel alloy, with the ability to be potentially applied to commercial alloys.