A novel multicomponent high-Cr CoNi-based superalloy with superior comprehensive performance was prepared,and the evaluation of its high-temperature microstructural stability,oxidation resistance,and mechanical proper...A novel multicomponent high-Cr CoNi-based superalloy with superior comprehensive performance was prepared,and the evaluation of its high-temperature microstructural stability,oxidation resistance,and mechanical properties was conducted mainly using its cast polycrystalline alloy.The results disclosed that the morphology of theγ′phase remained stable,and the coarsening rate was slow during the long-term aging at 900–1000℃.The activation energy forγ′precipitate coarsening of alloy 9CoNi-Cr was(402±51)kJ/mol,which is higher compared with those of CMSX-4 and some other Ni-based and Co-based superalloys.Importantly,there was no indica-tion of the formation of topologically close-packed phases during this process.All these factors demonstrated the superior microstructural stability of the alloy.The mass gain of alloy 9CoNi-Cr was 0.6 mg/cm^(2) after oxidation at 1000℃ for 100 h,and the oxidation resistance was comparable to advanced Ni-based superalloys CMSX-4,which can be attributed to the formation of a continuous Al_(2)O_(3) protective layer.Moreover,the compressive yield strength of this cast polycrystalline alloy at high temperatures is clearly higher than that of the conventional Ni-based cast superalloy and the compressive minimum creep rate at 950℃ is comparable to that of the conventional Ni-based cast superalloy,demonstrating the alloy’s good mechanical properties at high temperature.This is partially because high Cr is bene-ficial in improving theγandγ′phase strengths of alloy 9CoNi-Cr.展开更多
The alloying effects of Ni,W and Cron the microstructural stability of CoNi-base alloys were investigated using a multicomponent diffusion multiple after being aged at 1000℃ for 1000 h.The diffusion multiple was care...The alloying effects of Ni,W and Cron the microstructural stability of CoNi-base alloys were investigated using a multicomponent diffusion multiple after being aged at 1000℃ for 1000 h.The diffusion multiple was carefully designed based on thermodynamic calculations.The relationships between alloy compositions and microstructural characteristics were established over a large compositional range using this single sample,and the alloying effects of Ni,W and Cron the elemental partitioning behaviors betweenγ and γ' two phases were thermodynamically analyzed using high-throughput calculation.The results together show that an increase of Ni content increases the γ' volume faction in the long-term aged microstructures.However,the higher Ni content leads to the precipitation of the χ phase by promoting the partitioning of W from the γ' phase to the γ phase.The decrease of W content dramatically reduces theγ' volume faction,but the addition of Cr can properly counteract this effect by promoting the partitioning of Al and Ti from the γ phase to the γ' phase.This study will be helpful for accelerating the development of novel γ'-strengthened multicomponent CoNi-base alloys,as well as providing experimental data to improve the thermodynamic database.展开更多
Oxidation behavior of γ’-strengthened CoNi-base superalloys was investigated with isothermal oxidation tests conducted in air at 800 and 900℃,respectively,for 100 h.It is observed that both 30Ni-10Al-4W-4Ti-2Ta(4W2...Oxidation behavior of γ’-strengthened CoNi-base superalloys was investigated with isothermal oxidation tests conducted in air at 800 and 900℃,respectively,for 100 h.It is observed that both 30Ni-10Al-4W-4Ti-2Ta(4W2Ta)and 30Ni-10Al-5W-4Ti-1Ta(5W1Ta)alloys exhibit a three-layered oxide scale structure after oxidation.Addition of Ta increases oxidation mass gain of Co Ni-based high-temperature alloys,but the effects on the type and distribution of oxidation products are not significant.However,the oxidation temperature has a great influence on oxide surface morphology and oxidation mechanisms for those two alloys.After oxidation at 800℃,the outermost oxide film contains Co_(3)O_(4),CoO,and NiO,and when the oxidation temperature is 900℃,the outermost oxide film contains only CoO.展开更多
The effects of B addition on microstructure and mechanical properties of aγ′-strengthened CoNi-base superalloy are investigated.The addition of B leads to a substantial increase in the volume fraction of both the eu...The effects of B addition on microstructure and mechanical properties of aγ′-strengthened CoNi-base superalloy are investigated.The addition of B leads to a substantial increase in the volume fraction of both the eutectic structure and borides.The CoNi-base alloy shows a high solubility limit for the element B.Borides become noticeable in the area surrounding the eutectic structure after the B level exceeds 0.46 at.%.It is found that the compression property and stress rupture life of the 4W2Ta alloys exhibit an initial rise followed by a subsequent drop as the B content gradually increases from 0.08 to 0.78 at.%.The 4W2Ta0.46B alloy demonstrates the most excellent high-temperature strength and stress rupture life,revealing that a moderate amount of B in the alloy noticeably enhances its mechanical properties by enhancing the grain boundary cohesion.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52331005,52201100,52171095,and 92060113)the China Postdoctoral Science Foundation(No.2022M710346)+2 种基金Science and Technology on Advanced High Temperature Structural Materials Laboratory,China(No.6142903210207)the Fundamental Research Funds for the Central Universities,China(No.FRF-GF-20-30B)the National Key Research and Development Program of China(No.2017YFB0702902).
文摘A novel multicomponent high-Cr CoNi-based superalloy with superior comprehensive performance was prepared,and the evaluation of its high-temperature microstructural stability,oxidation resistance,and mechanical properties was conducted mainly using its cast polycrystalline alloy.The results disclosed that the morphology of theγ′phase remained stable,and the coarsening rate was slow during the long-term aging at 900–1000℃.The activation energy forγ′precipitate coarsening of alloy 9CoNi-Cr was(402±51)kJ/mol,which is higher compared with those of CMSX-4 and some other Ni-based and Co-based superalloys.Importantly,there was no indica-tion of the formation of topologically close-packed phases during this process.All these factors demonstrated the superior microstructural stability of the alloy.The mass gain of alloy 9CoNi-Cr was 0.6 mg/cm^(2) after oxidation at 1000℃ for 100 h,and the oxidation resistance was comparable to advanced Ni-based superalloys CMSX-4,which can be attributed to the formation of a continuous Al_(2)O_(3) protective layer.Moreover,the compressive yield strength of this cast polycrystalline alloy at high temperatures is clearly higher than that of the conventional Ni-based cast superalloy and the compressive minimum creep rate at 950℃ is comparable to that of the conventional Ni-based cast superalloy,demonstrating the alloy’s good mechanical properties at high temperature.This is partially because high Cr is bene-ficial in improving theγandγ′phase strengths of alloy 9CoNi-Cr.
基金supported by the National Key Research and Development Program of China(No.2017YFB0702902)the National Natural Science Foundation of China(No.51771019)the Guangdong Province Key Area R&D Program(No.2019B010943001)。
文摘The alloying effects of Ni,W and Cron the microstructural stability of CoNi-base alloys were investigated using a multicomponent diffusion multiple after being aged at 1000℃ for 1000 h.The diffusion multiple was carefully designed based on thermodynamic calculations.The relationships between alloy compositions and microstructural characteristics were established over a large compositional range using this single sample,and the alloying effects of Ni,W and Cron the elemental partitioning behaviors betweenγ and γ' two phases were thermodynamically analyzed using high-throughput calculation.The results together show that an increase of Ni content increases the γ' volume faction in the long-term aged microstructures.However,the higher Ni content leads to the precipitation of the χ phase by promoting the partitioning of W from the γ' phase to the γ phase.The decrease of W content dramatically reduces theγ' volume faction,but the addition of Cr can properly counteract this effect by promoting the partitioning of Al and Ti from the γ phase to the γ' phase.This study will be helpful for accelerating the development of novel γ'-strengthened multicomponent CoNi-base alloys,as well as providing experimental data to improve the thermodynamic database.
基金financially supported by the National Natural Science Foundation of China (51831007)the National Major Science and Technology Projects of China (J2019-VII-0002-0142)
文摘Oxidation behavior of γ’-strengthened CoNi-base superalloys was investigated with isothermal oxidation tests conducted in air at 800 and 900℃,respectively,for 100 h.It is observed that both 30Ni-10Al-4W-4Ti-2Ta(4W2Ta)and 30Ni-10Al-5W-4Ti-1Ta(5W1Ta)alloys exhibit a three-layered oxide scale structure after oxidation.Addition of Ta increases oxidation mass gain of Co Ni-based high-temperature alloys,but the effects on the type and distribution of oxidation products are not significant.However,the oxidation temperature has a great influence on oxide surface morphology and oxidation mechanisms for those two alloys.After oxidation at 800℃,the outermost oxide film contains Co_(3)O_(4),CoO,and NiO,and when the oxidation temperature is 900℃,the outermost oxide film contains only CoO.
基金supported by the National Natural Science Foundation of China(No.51831007).
文摘The effects of B addition on microstructure and mechanical properties of aγ′-strengthened CoNi-base superalloy are investigated.The addition of B leads to a substantial increase in the volume fraction of both the eutectic structure and borides.The CoNi-base alloy shows a high solubility limit for the element B.Borides become noticeable in the area surrounding the eutectic structure after the B level exceeds 0.46 at.%.It is found that the compression property and stress rupture life of the 4W2Ta alloys exhibit an initial rise followed by a subsequent drop as the B content gradually increases from 0.08 to 0.78 at.%.The 4W2Ta0.46B alloy demonstrates the most excellent high-temperature strength and stress rupture life,revealing that a moderate amount of B in the alloy noticeably enhances its mechanical properties by enhancing the grain boundary cohesion.
