Influence of direction of notch on thermal fatigue property of a directionally solidified nickel base superalloy

Abstract

Thermal fatigue property of a directionally solidified nickel base superalloy at the condition of different notched orientation and upper temperatures was investigated. The results show that cycle numbers of crack initiation decrease, propagation rate of crack increases and resistance of thermal fatigue reduces with the rise of upper temperature. Thermal fatigue property of the specimen with the notched direction vertical to orientation of dendrite growth (DZ319T) is superior to that of the specimen with the notched direction parallel to orientation of dendrite growth (DZ319L). DZ319L alloy initiates thermal fatigue crack by carbide and propagates along the direction of carbide distribution, which resultes in big propagation rate and poor thermal fatigue property. Crack initiation of DZ319T alloy is mainly by oxidized cavity. The join of oxidized cavity makes crack propagate. There are two cracks in DZ319T alloy, which greatly drops the stress concentration near the notch and decreases the propagation rate of crack. DZ319T alloy has excellent thermal fatigue property.

Thermal fatigue behaviour of Al–Si coated Inconel 713 LC

“…The growth direction of primary dendrites is considered as ⟨110⟩. If the already formed notch is considered as a predetermined crack, ⟨110⟩ orientation is subjected to the maximum shearing stress, and therefore, initiation and propagation of crack along this orientation would be promoted, as reported by Xia et al 14 In a cast polycrystalline structure, interdendritic regions are vulnerable places to thermal fatigue and, hence, are preferred as the crack sources and propagation area.…”

Low cycle fatigue behavior and fracture mechanism of a directionally solidified CM247 LC superalloy

“…The directionally-solidified CM247 LC is one of the most commonly used superalloys for high-temperature applications, which are vastly used in the blades of gas turbines 1,7,8 . The appropriate mechanical properties at high temperatures are a consequence of the γ' precipitates in the matrix of γ phase 9,10 . The γ and γ' phases are generally solid-solution strengthened.…”

Room temperature tensile behaviour of K640S Co-based superalloy

“…K640S alloy is a typical cobalt-based superalloy mainly with carbide precipitation strengthening [1][2][3]. With excellent hot corrosion resistance and thermal fatigue resistance, K640S alloy has been widely used in manufacturing aeroengines and gas turbine guide vanes [4][5][6]. The structure of K640S alloy mainly consists of γ matrix and M 7 C 3 and M 23 C 6 -type carbide [7][8][9].…”