Effects of Cooling Hole Addition on Creep Lifetime of Nickel-based Single Crystal Superalloy DD6 nickel-based single crystal superalloy DD6, creep lifetime, dislocations, stress concentration
SHENG Chuande1, XIONG Xinhong1,2,, ZHU Chao1, DAI Pengdan1, ZHANG Qiaoxin3
1 School of Logistics Engineering, Wuhan University of Technology, Wuhan 430063 2 Engineering Research Center of Port Logistics Technology and Equipment, Ministry of Education, Wuhan University of Technology, Wuhan 430063 3 School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070
Abstract: Under a constant applied normal stress of 200 MPa and a temperature of 1 000 ℃, the creep experiments of two nickel-based single crystal superalloy DD6 samples, with a cooling hole (fabricated by circular scanning and trepanning drilling of Femtosecond Laser) and without cooling hole, were conducted. The experiments showed that the creep lifetime of the DD6 sample with a cooling hole was much shorter than that of the sample without cooling hole. With SEM and TEM observing the microstructure before and after creep, it was found that the deformation in the sample without cooling hole was the evenly spread out slip of the dislocations in the plastic matrix phase (γ phase). While the creep deformation in the sample with a cooling hole was mainly localized around the hole, which led to a large number of dislocation multiplication creating a large microscopic stress concentration at the γ/γ′ interface enough to cut through the precipitates, the brittle and stronger γ′ phase, and thus the crack propagation was then much accelerated due to the loss of resistance, and the creep life was shortened significantly.
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2019, Vol. 33 
