Abstract
High temperature creep resistance is a critical characteristic of Ni-based single crystal (SX) superalloys. In this work, the creep behavior of a Ni-based SX superalloy was in situ characterized at 980 °C by ultraviolet (UV) imaging combined two-dimensional digital image correlation (DIC) in vacuum environment. The surface pattern was fabricated to maintain stable over 65 h at 980 °C. The pattern images captured by UV imaging were analyzed using mean gray value and the full-field strain map of creep deformation was obtained. A laser displacement senor (LDS) was employed for measuring the creep strain on the specimen for comparison. The creep deformation result shows a good agreement between DIC and LDS, the microstructure of the different creep areas on the specimens also demonstrate that the results of DIC are reliable. The in situ creep characterization by UV-DIC shows a great potential for investigating creep behaviors at high temperatures.
Highlights
Ni-based single crystal (SX) superalloys with their excellent high temperature creep resistance have been extensively used for advance aero-engines’ turbine blade [1,2,3]
The ultra violet (UV)-digital image correlation (DIC) system records the deformed image of the specimen surface in every 10 min
It is obvious that all these images provided high contrast and sharpness, which confirmed the capability of the UV imaging system in suppressing the adverse influence of thermal radiation at elevated temperature
Summary
Ni-based single crystal (SX) superalloys with their excellent high temperature creep resistance have been extensively used for advance aero-engines’ turbine blade [1,2,3]. Lyons et al [12] used DIC to determine the thermally and mechanically induced strain of the Inconel 718 alloy at temperatures up to 650 ◦ C In their work, they observed that the thermal radiation of a sample over 750 ◦ C was brighter than the illuminated white light source which results in a failure of DIC analysis. This is mainly because long-term monitoring of creep behavior by DIC faces several challenges: First, intensified thermal radiation of the heated samples at higher temperatures will result in serious “decorrelation effect” above 600 ◦ C that restricted the deformation measurement. In previous work [22], a direct current heating system (DCHS) with a high vacuum environment below 10−4 Pa was designed and established for high temperature observation for DIC measurement, and the DIC results showed a full-field strain map of SX specimens during tensile testing. Structure of the UV optical system [18]
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