Corporate Effects of Temperature and Strain Range on the Low Cycle Fatigue Life of a Single-Crystal Superalloy DD10

Meng

et al. 2018

The influence of crystal orientations on the low-cycle fatigue (LCF) behavior of a 3Re-bearing Ni-based single-crystal superalloy at 980°C has been investigated. It is found that the orientation dependence of the fatigue life not only depends on the elastic modulus, but also the number of active slip planes and the plasticity of materials determine the LCF life, especially for the [011] and [111] specimens. The [011] and [111] specimens with better plasticity withstand relatively concentrated inelastic deformation caused by fewer active slip planes, compared to the [001] specimens resisting widespread deformation caused by a higher number of active slip planes. Additionally, fatigue fracture is also influenced by cyclic plastic deformation mechanisms of the alloy with crystal orientations, and the [001] specimens are plastically deformed by wave slip mechanism and fracture along the non-crystallographic plane, while the [011] and [111] specimens are plastically deformed by planar slip mechanism and fracture along the crystallographic planes. Moreover, casting pores, eutectics, inclusions and surface oxide layers not only initiate the crack, but also reduce the stress concentration around crack tips. Our results throw light upon the effect of inelastic strain on the LCF life and analyze the cyclic plastic deformation for the alloy with different orientations.

Section: Discussionmentioning

confidence: 99%

Effects of Crystal Orientations on the Low-Cycle Fatigue of a Single-Crystal Nickel-Based Superalloy at 980 °C

Meng

et al. 2018

“…In order to improve fuel efficiency, single-crystal superalloys have been widely used [1,2] in aero engines and turbine engines. Due to the complexity of casting process and large doses of precious metal usage, single-crystal superalloys are much expensive.…”

Section: Introductionmentioning

confidence: 99%

Effects of Substrate Crystallographic Orientations on Microstructure in Laser Surface-Melted Single-Crystal Superalloy: Theoretical Analysis

Wang

Liang

Zhou

et al. 2016

A geometric analysis technique for crystal growth and microstructure development in single-crystal welds had been previously developed. And the effect of welding conditions on the tendency of stray grains formation during solidification was researched. In the present work, these analytical methods were further extended. Combined with an original vectorization method, a 3D Rosenthal solution was used to determine thermal conditions of the welds. Afterward, the dendrite growth orientation, the dendrite growth velocity and the thermal gradient along dendrite direction were calculated and lively plotted. Finally, the tendency of stray grains formation in the solidification front was forecasted and its distribution was presented with a 3D plot. The results indicate that substrate orientation has some impacts on the crystal growth pattern, dendrite growth velocity, distribution of thermal gradient and stray grain. Based on the research methods proposed in this work, any substrate crystallographic orientation can be studied, and predicted stray grains distribution can be visualized.

“…The different initiation and propagation paths of thermal fatigue cracks for the three-state specimens are schematically illustrated in Fig.11. During thermal fatigue test, thermal stress can be formed at the carbide/matrix interface due to the different thermal expansion coefficients[6,7,18,19]. In addition, these carbides are hard and brittle.…”

mentioning

confidence: 99%

The Intrinsic Relationship Between Microstructure Evolution and Thermal Fatigue Behavior of a Single-Crystal Cobalt-Base Superalloy

Gui

Zhang

Yang

et al. 2017

The intrinsic relationship between the microstructure evolution and thermal fatigue behavior of a single-crystal cobalt-base superalloy has been investigated. The thermal fatigue tests are performed cyclically between room temperature and 1050°C using V-notch plate specimens. Three states of thermal fatigue specimens are selected: the as-cast, solutionized as well as aged states. The solution treatment is carried out at 1260°C for 24 h, which results in the dissolution of most of interdendritic continuous primary carbides. The subsequent aging treatment is carried out at 1100°C for 100 h after solution treatment, resulting in the precipitation of a profusion of chain-and point-like M 23 C 6 carbides in the matrix. The results indicate that the heat treatment can improve the thermal fatigue properties of the alloy and the effect of the solution treatment is more prominent than that of the aging treatment. The coarse and continuously distributed primary carbides in the as-cast state are changed into small and discontinuous distribution by heat treatment, which is the dominant factor in the improvement of thermal fatigue property. Additionally, the effect of oxidation behavior during thermal fatigue test on the thermal fatigue behavior is also studied.