The microstructure and phase precipitate behavior and their effects on the room temperature hardness and impact toughness of Inconel 740H aged at 750 ℃ for 10000 h were investigated by SEM, TEM and mechanical analys...The microstructure and phase precipitate behavior and their effects on the room temperature hardness and impact toughness of Inconel 740H aged at 750 ℃ for 10000 h were investigated by SEM, TEM and mechanical analysis. The as-received alloy shows a low hardness value of HB 168 and a highest toughness value of 96 J. After an aging treatment at 800 ℃ for 16 h and cooled in air （standard heat-treated condition）, fine γ′ phase particles precipitate within the grains and small carbide particles are located at the grain boundaries. The hardness increases to HB 304 and the impact toughness decreases to 15 J after standard heat treatment. A maximum hardness value of HB 331 is achieved for the alloy aged at 750 ℃ for 300 h. With increasing the aging time from 300 to 10000 h, a decrease of the hardness and toughness is observed along with an enhanced quantity of M23C6 particles and the coarsening of γ′ phase.展开更多
A novel nickel-based superalloy INCONEL 740 was under development for application in ultra-supercritical superheater tubers above 750℃. The precipitation behaviors of η phase and γ' particles of the alloy were ...A novel nickel-based superalloy INCONEL 740 was under development for application in ultra-supercritical superheater tubers above 750℃. The precipitation behaviors of η phase and γ' particles of the alloy were investigated through experimental study and phase computation. Experimental results showed that η phase formed a Widmanst?tten pattern structure following long-term exposure at elevated temperatures and that the coarsening of γ' particle follows a cube rate law:r-3 ∝ t. Thermodynamic calculation results showed that Al and Ti had an important effect on the precipitation behavior of γ' andη phases. Two suggested novel modified alloys, wherein the Al and Ti contents were modified, were designed and melted for the experimental study. The preliminary results indicated that the modified alloys exhibited higher structural stability following long-term exposure at 750℃ till 5000h.展开更多
The preliminary chemical composition optimization and heat treatment parameters of Inconel 740H were investigated systematically. Six heats of experimental alloys （designated as heat 401 to heat 406） with varied che...The preliminary chemical composition optimization and heat treatment parameters of Inconel 740H were investigated systematically. Six heats of experimental alloys （designated as heat 401 to heat 406） with varied chemi- cal compositions were subjected to standard heat treatment at four different solution temperatures. Due to its superi- or combination of strength, ductility, and toughness together with its minor mechanical property changes at different solution temperatures, heat 405 was chosen as an optimized one to conduct further heat treatment investigations. The evolution of grain size with solution temperature for heat 405 was studied and the optimal solution temperature was determined. After solution treatment at the optimal temperature, four different cooling rates were applied to investi- gate the effect of cooling rate on the size distribution modal and mean radius of the γ′ precipitates. No bi-modal size distribution of γ′ precipitates was found for all cooling rates and water cooling was recommended for Inconel 740H. In addition, the effect of pre-aging at 800 ℃ for 16 h on the microstrueture of Inconel 740H aged for a long time was studied. It is found that pre-aging at 800 ℃ would result in bi-modal size distribution of γ′ precipitates after long time aging at 750 ℃ compared with mono modal size distribution in samples without pre-aging, which might be caused by the difference in initial size distribution modal before Ostwald ripening of γ′ precipitates in samples with and without pre-aging at 800 ℃.展开更多
基金Project(TN-15-TYK05) supported by the Research and Development Fund of Thermal Power Research Institute(TPRI),ChinaProject(2012AA050501)supported by the National High-tech Research and Development Program of China
文摘The microstructure and phase precipitate behavior and their effects on the room temperature hardness and impact toughness of Inconel 740H aged at 750 ℃ for 10000 h were investigated by SEM, TEM and mechanical analysis. The as-received alloy shows a low hardness value of HB 168 and a highest toughness value of 96 J. After an aging treatment at 800 ℃ for 16 h and cooled in air （standard heat-treated condition）, fine γ′ phase particles precipitate within the grains and small carbide particles are located at the grain boundaries. The hardness increases to HB 304 and the impact toughness decreases to 15 J after standard heat treatment. A maximum hardness value of HB 331 is achieved for the alloy aged at 750 ℃ for 300 h. With increasing the aging time from 300 to 10000 h, a decrease of the hardness and toughness is observed along with an enhanced quantity of M23C6 particles and the coarsening of γ′ phase.
文摘A novel nickel-based superalloy INCONEL 740 was under development for application in ultra-supercritical superheater tubers above 750℃. The precipitation behaviors of η phase and γ' particles of the alloy were investigated through experimental study and phase computation. Experimental results showed that η phase formed a Widmanst?tten pattern structure following long-term exposure at elevated temperatures and that the coarsening of γ' particle follows a cube rate law:r-3 ∝ t. Thermodynamic calculation results showed that Al and Ti had an important effect on the precipitation behavior of γ' andη phases. Two suggested novel modified alloys, wherein the Al and Ti contents were modified, were designed and melted for the experimental study. The preliminary results indicated that the modified alloys exhibited higher structural stability following long-term exposure at 750℃ till 5000h.
基金Sponsored by High-Tech Research and Development Project of China(2102AA03A501)
文摘The preliminary chemical composition optimization and heat treatment parameters of Inconel 740H were investigated systematically. Six heats of experimental alloys （designated as heat 401 to heat 406） with varied chemi- cal compositions were subjected to standard heat treatment at four different solution temperatures. Due to its superi- or combination of strength, ductility, and toughness together with its minor mechanical property changes at different solution temperatures, heat 405 was chosen as an optimized one to conduct further heat treatment investigations. The evolution of grain size with solution temperature for heat 405 was studied and the optimal solution temperature was determined. After solution treatment at the optimal temperature, four different cooling rates were applied to investi- gate the effect of cooling rate on the size distribution modal and mean radius of the γ′ precipitates. No bi-modal size distribution of γ′ precipitates was found for all cooling rates and water cooling was recommended for Inconel 740H. In addition, the effect of pre-aging at 800 ℃ for 16 h on the microstrueture of Inconel 740H aged for a long time was studied. It is found that pre-aging at 800 ℃ would result in bi-modal size distribution of γ′ precipitates after long time aging at 750 ℃ compared with mono modal size distribution in samples without pre-aging, which might be caused by the difference in initial size distribution modal before Ostwald ripening of γ′ precipitates in samples with and without pre-aging at 800 ℃.
