The corrosion behavior of environmental barrier coatings(EBCs)directly affects the service life and stability of ceramic matrix composite(CMC)structural parts in the aero-engines.The silicon carbide(SiC)whisker toughe...The corrosion behavior of environmental barrier coatings(EBCs)directly affects the service life and stability of ceramic matrix composite(CMC)structural parts in the aero-engines.The silicon carbide(SiC)whisker toughening phase and c-AlPO_(4) bonding phase are firstly used to improve the service life of novel tri-layer Yb_(2)Si_(2)O_(7)/mullite/SiC EBCs in the burner rig test.The formation of penetrating cracks in Yb_(2)Si_(2)O_(7)/mullite/SiC coating caused the failure of coating at 1673 K.The SiC whiskers in mullite middle coating significantly inhibited the formation of penetrating cracks in Yb_(2)Si_(2)O_(7)/mullite/SiC coating,and efficiently prevented the oxidation of carbon fiber reinforced silicon carbide(C_(f)/SiC)samples for 360-min thermal cycles(24 times)with a weight loss of 6.19×10^(−3) g·cm^(−2).Although c-AlPO_(4) particles further improved the service life of SiC_(w)-mullite(SM)coating,the overflow of PO_(x) gas aggravated the formation and expansion of cracks in the Yb_(2)Si_(2)O_(7) outer coating,and caused the service life of overall Yb_(2)Si_(2)O_(7)/c-AlPO_(4)-SiC_(w)-mullite(ASM)/SiC coating to be slightly lower than that of Yb_(2)Si_(2)O_(7)/SM/SiC coating.This study guides the design of modified tri-layer EBCs with long service life in high-temperature and high-speed gas environment.展开更多
The influence of gas high-temperature hot corrosion(HTHC) pre-exposure on low-cycle fatigue(LCF)behavior was characterized for the directionally solidified(DS) Ni-based superalloy DZ125. Fatigue tests were carried out...The influence of gas high-temperature hot corrosion(HTHC) pre-exposure on low-cycle fatigue(LCF)behavior was characterized for the directionally solidified(DS) Ni-based superalloy DZ125. Fatigue tests were carried out at 850 ℃ in the pre-exposed and unexposed specimens for 2, 15 and 25 h. Experimental results show that the porous corrosion scale and γ′-depleted layer formed in gas hot corrosion condition alter the crack initiation mechanisms of the superalloy. Fatigue cracks of the pre-exposed specimens originate from multiple surface locations where spalling of the corrosion products occur,while nucleation of unexposed specimen begins in the defects close to the surface. There is a significant reduction in LCF behavior for pre-exposed specimens in comparison with unexposed specimens.展开更多
基金funded by the National Key R&D Program of China(Grant Nos.2021YFB3703800 and 2021YFB3703802)National Natural Science Foundation of China(Grant No.52102122)+1 种基金National Key Laboratory of Science and Technology on High-strength Structural Materials,Central South University(Grant No.SYSJJ2021LWS01)China Postdoctoral Science Foundation(Grant No.2022M711540).
文摘The corrosion behavior of environmental barrier coatings(EBCs)directly affects the service life and stability of ceramic matrix composite(CMC)structural parts in the aero-engines.The silicon carbide(SiC)whisker toughening phase and c-AlPO_(4) bonding phase are firstly used to improve the service life of novel tri-layer Yb_(2)Si_(2)O_(7)/mullite/SiC EBCs in the burner rig test.The formation of penetrating cracks in Yb_(2)Si_(2)O_(7)/mullite/SiC coating caused the failure of coating at 1673 K.The SiC whiskers in mullite middle coating significantly inhibited the formation of penetrating cracks in Yb_(2)Si_(2)O_(7)/mullite/SiC coating,and efficiently prevented the oxidation of carbon fiber reinforced silicon carbide(C_(f)/SiC)samples for 360-min thermal cycles(24 times)with a weight loss of 6.19×10^(−3) g·cm^(−2).Although c-AlPO_(4) particles further improved the service life of SiC_(w)-mullite(SM)coating,the overflow of PO_(x) gas aggravated the formation and expansion of cracks in the Yb_(2)Si_(2)O_(7) outer coating,and caused the service life of overall Yb_(2)Si_(2)O_(7)/c-AlPO_(4)-SiC_(w)-mullite(ASM)/SiC coating to be slightly lower than that of Yb_(2)Si_(2)O_(7)/SM/SiC coating.This study guides the design of modified tri-layer EBCs with long service life in high-temperature and high-speed gas environment.
基金financially supported by the National Natural Science Foundation of China (No. 51571010)the National Basic Research Program of China (No. 2015CB057400)
文摘The influence of gas high-temperature hot corrosion(HTHC) pre-exposure on low-cycle fatigue(LCF)behavior was characterized for the directionally solidified(DS) Ni-based superalloy DZ125. Fatigue tests were carried out at 850 ℃ in the pre-exposed and unexposed specimens for 2, 15 and 25 h. Experimental results show that the porous corrosion scale and γ′-depleted layer formed in gas hot corrosion condition alter the crack initiation mechanisms of the superalloy. Fatigue cracks of the pre-exposed specimens originate from multiple surface locations where spalling of the corrosion products occur,while nucleation of unexposed specimen begins in the defects close to the surface. There is a significant reduction in LCF behavior for pre-exposed specimens in comparison with unexposed specimens.
