scholarly journals Effect of Nb on Microstructure and Mechanical Property of Novel Powder Metallurgy Superalloys during Long-Term Thermal Exposure

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 656
Author(s):  
Dingmao Zhou ◽  
Xianjue Ye ◽  
Jianwei Teng ◽  
Chao Li ◽  
Yunping Li
Keyword(s):  
Mechanical Properties ◽  
Exposure Time ◽  
Shape Change ◽  
Lattice Misfit ◽  
Thermal Exposure ◽  
Average Diameter ◽  
Nb Addition ◽  
Microstructure And Mechanical Property ◽  
Size Increment

Microstructure and mechanical properties of novel Ni-20Co-12Cr superalloys, with and without Nb addition, were systematically studied during long-term thermal exposure. With increased exposure time, the average diameter of the γ′ precipitates increased in both alloys in succession; this is more obviously observed in alloy containing 1 wt% Nb (1Nb). It is suggested that Nb increased the γ′ coarsening rate by accelerating the diffusion of Al and Nb in γ matrix. In addition, the γ′ phase fraction is increased by about 4% in 1Nb compared to the alloy without Nb (0Nb). The morphology of the γ′ phase changed from near-spherical to cuboidal shape during exposure in both alloys. Due to the increased γ/γ′ lattice misfit by Nb addition, 1Nb alloy showed an earlier tendency of shape change. Vickers hardness results revealed that the overall hardness decreased with the exposure time because the size increment of the γ′ precipitate weakened the precipitates strengthening and Orowan strengthening.

Mechanical Properties of Epoxy Adhesive Under Thermal Aging and Their Chemical Degradation Behavior

2021 ◽  
Vol 21 (8) ◽  
pp. 4444-4449
Author(s):  
Bongjin Chung ◽  
Shin Sungchul ◽  
Jaeho Shim ◽  
Seongwoo Ryu
Keyword(s):  
Mechanical Properties ◽  
Thermal Aging ◽  
Photoelectron Spectroscopy ◽  
Thermal Exposure ◽  
Chain Scission ◽  
Epoxy Adhesive ◽  
Chemical Degradation ◽  
Adhesive Properties ◽  
Noticeable Reduction

Epoxy adhesive was analyzed under long term thermal aging and mechanical properties and chemical degradation were observed by X-ray photoelectron spectroscopy (XPS). Long term thermal exposure of epoxy causes a noticeable reduction in adhesive properties. We developed a predictive model of temperature and time dependent aging. The temperature dependent aging behavior of epoxy adhesive shows good agreement with conventional Arrhenius equations. Using XPS analysis, we also discovered a correlation between chemical degradation and the adhesive properties. Decay of C–C bonding ratio induced chain-scission of epoxy adhesive; increase of total numbers of C–O and C═O induced oxidation of epoxy adhesive during thermal exposure.

Influence of Thermal Exposure on the Microstructure, Surface Stability and Strength of a New Fe-Ni-Base Superalloy for A-USC Applications

2015 ◽  
Vol 816 ◽  
pp. 523-528 ◽  
Author(s):  
Zhi Hong Zhong ◽  
Yue Feng Gu ◽  
Yong Yuan ◽  
Zhan Shi ◽  
Yu Cheng Wu
Keyword(s):  
Yield Strength ◽  
Exposure Time ◽  
Low Cost ◽  
Thermal Exposure ◽  
Microstructural Stability ◽  
Surface Stability ◽  
Σ Phase ◽  
Good Oxidation Resistance ◽  
Base Superalloy

A low-cost, high-creep strength wrought Fe‒Ni-base superalloy for 700 °C advanced ultra-supercritical coal-fired power plant applications has been developed. The microstructural stability of this alloy during long-term exposures at 700 °C‒750 °C for up to 10000 h was investigated by SEM and TEM. The correlation between the microstructure evolution and the mechanical properties was studied. The experimental results showed that the major precipitates in the alloy were spherical γ′, MC and discrete M23C6 after the long-term exposure at 700 °C and 750 °C and no harmful phases, such as σ phase and η phase, were observed. The amount of M23C6 increased with exposure time at 700 °C while it decreased at 750 °C. During thermal exposure γ′ coarsened with increasing the exposure time and exposure temperature. Alloy showed good oxidation resistance due to the formation of external layer of Cr2O3. The yield strength of the alloy increased at first and then decreased with increasing exposure time at 700 °C, but it decreased gradually with increasing exposure time at 750 °C. The relationship between yield strength and the dominant deformation mechanisms of the alloy was discussed.

The Microstructure Evolution of a Nickel-Base Single Crystal Superalloy after Long-Term Aging

2015 ◽  
Vol 1088 ◽  
pp. 217-220 ◽  
Author(s):  
Yu Xian Jia
Keyword(s):  
Single Crystal ◽  
Exposure Time ◽  
Microstructure Evolution ◽  
Ageing Time ◽  
Thermal Exposure ◽  
Single Crystal Superalloy ◽  
Phase Precipitation ◽  
Tcp Phase ◽  
Nickel Base

Microstructure evolution of a nickel-base single crystal superalloy during thermal exposure at 982°C was investigated. The SEM studies revealed that the size of γ' phase increased and some of which linked together with the elongation of the exposure time. There is acicular phase precipitation after the long-term ageing treatment. The TCP phase is not increased by the increment of ageing time after reaching a certain amount. There are skeleton shape carbides precipitate after 100h and 300h. The amount of precipitated carbides decreases by the elongation of ageing time.

Microstructure and Mechanical Properties of a New Ni-Cr-Fe-W-Al Alloy for Advanced Ultra-Supercritical Power Plants

2015 ◽  
Vol 816 ◽  
pp. 586-593 ◽  
Author(s):  
Xian Chao Hao ◽  
Long Zhang ◽  
Xiu Juan Zhao ◽  
Tian Liang ◽  
Ying Che Ma ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Thermodynamic Calculation ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Prolonged Exposure ◽  
Thermal Exposure ◽  
Average Diameter ◽  
Al Alloy ◽  
Microstructural Stability

Optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermodynamic calculation were used to study the phase stability and precipitation in a Ni-Cr-Fe-W-Al alloy. Mechanical properties were also studied. The major precipitates after standard heat treatment or prolonged aging at 725 oC and 800 oC were M23C6 and γ′. M23C6 precipitated intergranularly. P-phase was not detected after thermal exposure, which was different from the results of thermodynamic calculation. The average diameter of γ′ increased with the increasing exposure temperature and time, and could be depicted by the LSW theory. Specimens in solution-annealed condition exhibited excellent ductility. During the prolonged exposure at 725 oC, tensile strength and ductility at room and elevated temperatures kept well, which means this alloy possessed good microstructural stability after a long time exposure.

Effects of Thickness on Thermal and Mechanical Properties of Air-Plasma Sprayed Thermal Barrier Coatings

2010 ◽  
Vol 658 ◽  
pp. 372-375 ◽  
Author(s):  
Sang Yeop Lee ◽  
Jae Young Kwon ◽  
Tae Woong Kang ◽  
Yeon Gil Jung ◽  
Ung Yu Paik
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Exposure Time ◽  
Gas Turbines ◽  
Microstructural Analysis ◽  
Thermal Exposure ◽  
Thermal Barrier ◽  
Air Plasma

Thermal barrier coating systems (TBCs) prepared by an air-plasma spray (APS) have been used to protect metallic components of gas turbines because of its economic advantage. To enhance the energy efficiency of gas turbine systems, the operating temperature is increased to over 1300 °C, which requires a new material with low thermal conductivity and an increase of TBC thickness. In this study we have focused the microstructure related to the thickness of TBC and their thermal properties, with specific attention to defect species as well as to its morphology with the thermal exposure time. Resintering of TBC happens during thermal exposure in a high temperature, resulting in the less strain tolerance and the higher thermal conductivity. In order to investigate the thermal properties of TBC related to the microstructural evolution, TBCs with different thicknesses of 200 µm, 400 µm, 600 µm, and 2000 µm were deposited on a flat graphite by the APS. The thermal exposure tests were conducted in different dwell time till 800h at 1100 °C. The thermal diffusivity is significantly increased after thermal exposures, depending on the thermal exposure time. Microstructural analysis clearly shows that the variation of thermal diffusivity is ascribed to the coalescence of small cracks and the resintering effect. The hardness values of TBCs are also increased as well. The relationship between mechanical properties and TBC thickness is discussed, including the effect of thickness on thermal properties.

EVOLUTIONS OF MICROSTRUCTURES AND MECHANICAL PROPERTIES OF TWO CAST Ni--BASED SUPERALLOYS DURING LONG--TERM THERMAL EXPOSURE

2010 ◽  
Vol 2010 (2) ◽  
pp. 213-220 ◽  
Author(s):  
Xuezhi QIN ◽  
Jianting GUO ◽  
Chao YUAN ◽  
Jieshan HOU ◽  
Lanzhang ZHOU ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Exposure ◽  
Microstructures And Mechanical Properties

Influence of Fe Content on Microstructure and Mechanical Properties of GH984 Alloy

2015 ◽  
Vol 816 ◽  
pp. 540-545
Author(s):  
Chang Shuai Wang ◽  
Ting Ting Wang ◽  
Mei Lin Tan ◽  
Yong An Guo ◽  
Jian Ting Guo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Structural Stability ◽  
Rupture Life ◽  
Thermal Exposure ◽  
Major Constituent ◽  
Microstructure And Mechanical Properties ◽  
Fe Content ◽  
Tcp Phase ◽  
The Cost

GH984 is an economic alloy due to the elimination of Co and its containing more than 20% Fe. As a major constituent of GH984 alloy, the Fe reduces the cost, but promotes the precipitation of TCP phase. In order to get an optimum alloy with desired balance among structural stability, mechanical properties and cost, the influence of Fe content on microstructure and mechanical properties of GH984 alloy was investigated in this paper. The results showed that the Fe content had no obvious influence on the major precipitates which were spherical γ′, blocky MC and discrete M23C6 at grain boundary after standard heat treatment, except the γ/γ ́ misfit. However, during long-term thermal exposure at 750°C, the decrease of the Fe content retarded the precipitation of η phase and enhanced the structural stability. The Fe content had no obvious influence on the tensile strength and ductility. At condition of 700°C/400MPa, the rupture life had not evident change, but the elongation decreased, the fractural model exhibited mix-fracture model and the characteristics of intergranular fracture became obvious with increasing the Fe content. It can be concluded that the decrease of Fe content can improve the structural stability and ductility.

scholarly journals Effect of Ni on Microstructure and Mechanical Property of a Co-Ti-V-Based Superalloy

Scanning ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Pengjie Zhou ◽  
Xinkang Gao ◽  
Dehang Song ◽  
Yinbing Liu ◽  
Jun Cheng
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Ultimate Strength ◽  
Lattice Misfit ◽  
Scanning Calorimetry ◽  
Slight Tendency ◽  
Ni Content ◽  
Temperature Lattice ◽  
Microstructure And Mechanical Property ◽  
Partition Behavior

The effect of Ni on microstructure, elemental partition behavior, γ ′ phase solvus temperature, lattice misfit between γ and γ ′ phases, and mechanical properties of the Co-8Ti-11V-xNi alloys was investigated. The result shows that the lattice misfit in the alloys decreases from 0.74% to 0.61% as the Ni content increases from 0 to 10%, and the average sizes of the cuboidal γ ′ phase were measured to be 312.10 nm, 112.86 nm, and 141.84 nm for the Co-8Ti-11V, Co-8Ti-11V-5Ni, and Co-8Ti-11V-10Ni, respectively. Ti, V, and Ni exhibit a slight tendency to partition into the γ ′ phase, while Co shows a slight tendency to partition into the γ phase. The solvus temperatures of the γ ′ phase were measured to be 1167°C, 1114°C, and 1108°C for the Co-8Ti-11V, Co-8Ti-11V-5Ni, and Co-8Ti-11V-10Ni alloys, respectively, by using differential scanning calorimetry (DSC). Moreover, the yield strength and ultimate strength of the Co-8Ti-11V, Co-8Ti-11V-5Ni, and Co-8Ti-11V-10Ni alloys were investigated, and the yield strength and ultimate strength of the 10Ni alloy were highest, at 219 MPa and 240 MPa. After compression at 1000°C, the dislocations cannot effectively shear the γ ′ phase in the 0Ni and 10Ni alloys, resulting in a relatively high compressive strength of the 0Ni and 10Ni alloys. However, the γ ′ phase of the 5Ni alloy is no longer visible, and its strength is the lowest.

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