High-Temperature, Time-Dependent Deformation and Densification of Unique Multi-Sheet Stacked Ni-Cr-Al Superalloy Foam

초록

This study investigates the fabrication and high-temperature time-dependent deformation of a multi-sheet stacked Ni-Cr-Al superalloy foam. The foam was produced by powder spraying to deposit alloying elements onto a pure Ni preform, followed by transient liquid phase sintering for homogenization and hot rolling for lamination and structural integrity. The fabricated foam exhibited a relative density of 4.55% and a porosity of 95.45%, with an average pore size of 2988.1 mu m in the rolling direction. Microstructural analysis confirmed a gamma(Ni, Cr) matrix and cuboidal gamma '(Ni3Al) precipitates (60.7% volume fraction). Time-dependent deformation tests at 923 K and 1073 K under constant compressive load revealed a significant difference in creep strain. At 923 K, 0.29 MPa (=0.387 sigma Y) stress resulted in a strain of 0.123, whereas at 1073 K, 0.14 MPa (=0.389 sigma Y) stress induced 0.246 strain, approximately twice the creep deformation. Despite higher creep strain at 1073 K, the stress exponent was lower (2.31 vs. 3.76 at 923 K). This is attributed to intersecting struts at sheet interfaces constraining free deformation through friction and interaction effects. Additionally, densification at strains over 30% increased relative density, which altered the initial stress effect and led to continuously decreasing creep deformation rates. Based on these results, the influence of strain hardening, densification, and structural interactions at sheet interfaces on the time-dependent deformation behavior of the block Ni-Cr-Al foam is discussed.

키워드