Gu Y.-L.,Aerospace Research Institute of Materials And Processing Technology |
Gu Y.-L.,Failure Analysis Center |
He Y.-H.,Aerospace Research Institute of Materials And Processing Technology |
He Y.-H.,Failure Analysis Center |
And 5 more authors.
Advanced Materials Research | Year: 2013
Low cycle fatigue failure tests of the powder metallurgical nickel based superalloy FGH96 at 550°C and 720 °C were carried out under total strain-controlled mode (R=-1). The fatigue failure behaviors were investigated by analyzing cyclic stress response and observing microstructure after fatigue through scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results show that FGH96 superalloy exhibits cyclic stability at 550 °C, and cyclic softening afterwards at 720 °C with Δε/2=0.4%, and of cyclic softening at 720 °C with Δε/2=0.7%. After high temperature low cycle fatigue, the γ′ precipitates are cuboidal for all samples. No coarsening of γ′ precipitates was detected at 550 °C and at 720 °C with Δε/2=0.4%, but small γ′ precipitates get together to be larger precipitates at 720 °C with Δε/2=0.7%. EBSD shows that the continuous small angle grain boundaries are produced during the fatigue. The small angle grain boundaries have a significant increase at 720 °C, especially that case at Δε/2=0.7%.© (2013) Trans Tech Publications, Switzerland.
Tu W.,Nanchang University |
Tu W.,Aerospace Research Institute of Materials And Processing Technology |
Tu W.,Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation |
Tu W.,Failure Analysis Center |
And 10 more authors.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2015
An actuator cylinder arm made of 40Cr steel was broken during the arm system tested. The feature and cause of the arm were analyzed by visual inspection, fracture view, metallographic examination and hardness testing. The results show that the fracture mode of the actuator cylinde arm is brittle overload fracture. Undesirable quenching and tempering cause a large number of ferrite existing in materials, which make brittleness of arm increasing, meanwhile decarburized layer existing inside wall, and the lack of the wall thickness reducing the carrying capacity of the arm are the internal reasons to overload fracture. Uneven force and impact load during the running of the arm are the external factors. The reasons that harmful structure of the arm are discussed by thermal simulation, and counter measures are proposed. ©, 2015, Chinese Mechanical Engineering Society of Heat Treatment. All right reserved.
Wei Z.-W.,Aerospace Research Institute of Materials And Processing Technology |
Wei Z.-W.,Failure Analysis Center |
Wei Z.-W.,Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation |
Zhao W.-X.,Aerospace Research Institute of Materials And Processing Technology |
And 17 more authors.
Procedia Engineering | Year: 2015
In this study, the K6509 cobalt-base superalloy were heat treated at different temperatures and the microstructure was detected by scanning electrical microscopy and electrical probe micro-analyzer. In as-cast K6509, the MC carbides are present as a discrete, blocky dispersion with a well-distributed Chinese script morphology and the eutectics (γ+M23C6) and (γ+M7C3) can be seen. With the temperature increasing, the MC arise degeneration. Below 1150oC, the script-like MC is dominant; reaching 1200oC, the particle and block of MC are dominant; reaching 1250oC, few script-like MC is present. In as-cast alloy, the M23C6 and M7C3 carbides are lamellar eutectic with matrix. When temperature is up to 1150oC, the eutectic (γ+M23C6) disappears; however, much eutectic (γ+M7C3) can be found. When the temperature reaches 1200oC, a large amount of eutectic M7C3 is dissolved, and some pores form in the matrix, and some zones rich in Cr form around the pores. When the temperature is above 1250oC, many pores form in the matrix, the cause of pores is need to be studied further. © 2015 The Authors.