High Temperature Creep Properties of Advanced Structural Materials: Creep Behavior of Steels and Multi-Principal Element Alloys
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee
Program Organizers: Gianmarco Sahragard-Monfared, University of California, Davis; Mingwei Zhang, Lawrence Berkeley National Lab; Jeffery Gibeling, University of California, Davis
Monday 2:00 PM
March 20, 2023
Room: Sapphire P
Location: Hilton
Session Chair: Gianmarco Sahragard-Monfared, University of California, Davis; Mingwei Zhang, Lawrence Berkeley National Laboratory; Jeffery Gibeling, University of California, Davis
2:00 PM Introductory Comments
2:05 PM
Role of Cr Content on Creep-rupture Performance in Alumina-forming Austenitic Alloys: Yukinori Yamamoto1; Qing-Qiang Ren1; Michael Brady1; 1Oak Ridge National Laboratory
A series of alumina-forming austenitic (AFA) alloys was developed as a new class of heat-resistant ferrous alloys which incorporated protective alumina-scale formation for improved oxidation/corrosion resistance in extreme environments. This study focused on the creep-rupture performance of AFA alloys with a variation of Cr content, i,e., Fe-(13.3-17.3)Cr-25Ni-4Al-1.5Nb-0.1C (wt.%), at 850°C and 30MPa to optimize the alloy composition balanced with oxidation resistance. The creep-rupture life of the alloy with 13.3 wt.% Cr was comparable to that of Ni-base alloy 625 at the test condition. However, the rupture-life monotonically decreased with increasing the Cr content. The performance degradation was correlated with the volume fraction changes in strengthening and deteriorating secondary phase precipitates, such as a reduction of B2-NiAl + Laves-Fe2Nb phase content and an increase of Sigma-FeCr phase. The oxidation resistance at 900°C in a water-vapor containing environment will also be discussed for optimization of the alloy composition with balanced properties.
2:25 PM
Creep Ratcheting of a HP+NbW (MA) Steam Methane Reformer Tube Alloy: Mackenzie Caughey1; Milo Kral1; 1University of Canterbury
Centrifugally cast austenitic steels such as ASTM HP+NbW (MA) are commonly used as steam-methane reformer tubes, operating at relatively low stress (15-40 MPa) and high temperature (> 0.5 TM). Traditional creep life assessment techniques based on inverse design approaches (e.g. Larson-Miller) have failed to accurately predict the life under cyclic thermal loading. Monotonic creep tests and cyclic creep ("creep ratcheting") experiments have been completed to provide strain rate data. Interrupted tests and post-mortem microstructural analysis will provide void fraction, size and spatial distribution data at varying stages. A modified Gurson-Tvergaard-Needleman-type model will utilize the strain rate and microstructural data to compare remaining life under cyclic conditions with monotonic conditions.
2:45 PM Invited
Creep Behaviors of High-entropy Alloys: Lia Amalia1; Di Xie1; Shuying Chen1; Weidong Li1; Dongyue Li2; Yong Zhang2; Chelsey Hargather3; Yanfei Gao1; Peter Liaw1; 1University of Tennessee; 2University of Science and Technology Beijing; 3New Mexico Institute of Mining and Technology
To ensure reliability and safety, creep resistance is an important property for high-temperature applications. Although the room-temperature behavior of high-entropy alloys has been studied extensively, the creep behavior has only been cursorily studied. Using data from the studies that have been performed, we are able to paint a picture of the creep behavior of high-entropy alloys. Creep can be characterized by conducting tests to reveal its uniaxial tension or compression behavior, stress-relaxation behavior, strain-rate-jump behavior, and nanoindentation creep behavior. From these tests, key deformation quantities could be obtained, such as the stress exponent (n), activation volume (V), and activation energy (Q). Furthermore, several non-neglectable factors affect the creep behavior of HEAs, including high entropy, lattice distortion, sluggish diffusion, stacking fault energy, alloying elements, and grain size, many of which are readily studied with computational techniques. The creep behavior of medium- and high-entropy alloys will be compared to commercial alloys.
3:15 PM
Mechanisms of Creep in Additively Manufactured NiCoCr and ODS-NiCoCr Multi-principal Element Alloys: Gianmarco Sahragard-Monfared1; Mingwei Zhang2; Timothy Smith3; Easo George4; Jeffery Gibeling1; 1University of California, Davis; 2Lawrence Berkeley National Laboratory; 3NASA Glenn Research Center; 4The University of Tennessee, Knoxville
Multi-principal element alloys (MPEA) have been proven to exhibit excellent room temperature and cryogenic strength and ductility. However, MPEAs with an FCC crystal processed by arc melting generally exhibit low strengths at elevated temperatures. Alternative manufacturing processes provide an opportunity to introduce dispersoids into the matrix to improve high temperature properties. In this study the influence of oxide dispersion strengthening (ODS) on the steady state and constant structure creep behavior of an MPEA produced by additive manufacturing (AM) is investigated. Constant stress and stress reduction creep tests were performed on AM-NiCoCr and an oxide dispersion strengthened variant containing one weight percent yttria (ODS-NiCoCr). The stress reduction tests enable the kinetics of deformation to be studied at constant structure, resulting in activation areas that reveal the rate controlling mechanisms of these MPEAs.