New Methodologies in Nanoindentation Creep
Accurately predicting creep behavior using nanomechanical testing
Traditional creep testing is time- and resource-intensive. Nanoindentation creep testing is more efficient, but has historically been limited in its accuracy due to the influx of fresh material as the contact area grows during indentation. Recent developments have worked to combat this limitation.
Watch this on-demand webinar to see:
- How new displacement control feedback algorithms improve time-dependent measurements on the TI 990 TriboIndenter.
- Recent work combining throughput, high-temperature indentation strain rate jump tests (SRJT) with only a few bulk dead-load creep tests to determine creep lifetime.
- Experimental datasets from Grade 91, FeCrAl, and oxide dispersion strengthened (ODS) steels that have been engineered for service under extreme conditions.
Abstracts
Advanced control methods for time dependence on the Bruker TI 990
Modern structural materials assessment demands high-throughput techniques with limited material. This is particularly challenging for time and temperature-dependent deformation of materials as traditional creep methods require a significant investment in time, personnel, equipment, and a relatively large volume of material.
Nanoindentation creep tests have long been used as a validation mechanism but have some drawbacks, including the influx of fresh material as the contact area grows during the indentation process. This is particularly an issue when the properties of interest may only exist near the surface. Here, new displacement control feedback algorithms are demonstrated that allow for the measurement of stress-relaxation in a drift-free manner.
Find out more about the technology featured in this webinar or our other solutions for nanomechanical testing:
High throughput assessment of creep behavior of advanced nuclear reactor alloys by nanoindentation
Current polycrystalline deformation models lack the spatially-resolved experimental quantification of dislocation cross-slip vs. dislocation climb-based mechanisms needed to address realistic operating temperatures for heterogeneous microstructures for service in nuclear reactors. This recent work demonstrates that a combination of high-throughput, high-temperature indentation Strain Rate Jump Tests (SRJT) and a few bulk dead-load creep tests is sufficient to determine creep lifetime in Grade 91 ferritic-martensitic alloy.
This combination of techniques has the potential for order-of-magnitude improvements in the time necessary to determine creep time to rupture and subsequent alloy design and qualification. Using a combined model/experiment approach, this testing provides the data needed to calculate creep lifetime predictions based on the well-established Larson-Miller Parameter (LMP). This stands in stark contrast to the dozens of bulk samples currently needed for a state-of-the-art creep data set.
We show that elevated temperature strain rate jump testing can provide insight into the critical parameters (strain rate or stress exponent, activation volume, activation energy for diffusion) that describe the site-specific, or aggregate dominant creep mechanisms for a given set of creep conditions. We will describe the transitions in mechanisms between room and elevated temperatures in terms of a microstructurally-informed model, and experimental data sets from Grade 91, FeCrAl, and Oxide Dispersion Strengthened (ODS) steels that have been engineered for service under extreme conditions.
Authors:
- Nathan A. Mara, University of Minnesota-Twin Cities
- Minh-Tam Hoang, University of Minnesota-Twin Cities
- Moujhuri Sau, University of Minnesota-Twin Cities
- Kevin Schmalbach, Bruker Nano Surfaces
- Eric Hintsala, Bruker Nano Surfaces
- Douglas Stauffer, Bruker Nano Surfaces
- Jobin K. Joy, Los Alamos National Laboratory
- Laurent Capolungo, Los Alamos National Laboratory
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Speakers
Douglas Stauffer, Ph.D.
Senior Manager of NI Applications Development
Prof. Nathan Mara, University of Minnesota