熱處理對IN 718鎳基超合金多孔金屬 微結構和機械性質之影響;Effect of heat treatment on microstructure and mechanical properties of IN 718 nickel based superalloy metal foam

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Title:	熱處理對IN 718鎳基超合金多孔金屬微結構和機械性質之影響;Effect of heat treatment on microstructure and mechanical properties of IN 718 nickel based superalloy metal foam
Authors:	李士揚;LI, SHIH-YANG
Contributors:	機械工程學系
Keywords:	鎳基超合金;IN 718;多孔合金;壓縮;Nickel based superalloy;IN 718;metal foams;compressive
Date:	2023-07-28
Issue Date:	2024-09-19 17:41:13 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究以光學顯微鏡(OM)、掃描式電子顯微鏡(SEM)、機械性質(硬度、壓縮)等試驗，探討燒結態、以及經兩種固溶(1020℃、940℃)、時效(兩段式720°C8h→620°C8h)處理之IN 718鎳基超合金多孔合金微結構和機械性質之影響。結果顯示，當合金燒結態時，可以觀察到微量的NbC碳化物存在於晶界上，此時合金微結構為γ基地和NbC碳化物析出相，其硬度、壓縮平台應力、及能量吸收值分別為219Hv、370MPa與63J/g。當進行1020℃(高溫)固溶處理後，其微結構為γ基地和NbC碳化物析出相所組成，其硬度、壓縮平台應力、及能量吸收值分別為189Hv、200MPa與29J/g。再經時效處理後，隨著強化相γ′相(Ni3(Al,Ti))及γ"相(Ni3(Nb))的析出，其硬度、壓縮平台應力、及能量吸收值分別提升至518Hv、520MPa與64J/g。其值均較燒結態大幅提高。當合金進行940℃(低溫)固溶處理後，觀察到大量針狀δ相(Ni3(Nb))析出於γ基地，此時合金微結構為γ基地與δ相(Ni3(Nb))所組成；其硬度、壓縮平台應力、及能量吸收值分別為232Hv、450MPa與66J/g。相較1020℃(高溫)固溶處理(189Hv)，硬度升高約6%，這是因為δ相(Ni3(Nb))於固溶處理的析出所導致，但也降低了基地過飽和程度，導致時效處理後，使γ"強化相析出量減少，時效處理後其硬度、平台應力、與能量吸收分別為434Hv、460MPa與70J/g，均低於1020℃(高溫)固溶時效合金，其值也均較燒結態大幅提高。 ;This study investigates the influence of sintering conditions and two different solid solution treatments (1020℃, 940℃) followed by aging treatment (two-stage: 720°C8h→620°C8h) on the microstructure and mechanical properties of porous IN 718 nickel-based superalloy. The examinations include optical microscopy (OM), scanning electron microscopy (SEM), and mechanical tests (hardness, compression). The results demonstrate that in the sintered state, trace amounts of NbC carbides can be observed at grain boundaries. The microstructure consists of a γ matrix and precipitates of NbC carbides. The corresponding hardness, compression plateau stress, and energy absorption value are 219Hv, 370MPa, and 63J/g, respectively. Following the high-temperature (1020℃) solid solution treatment, the microstructure is composed of a γ matrix and precipitates of NbC carbides. The hardness, compression plateau stress, and energy absorption value are reduced to 189Hv, 200MPa, and 29J/g, respectively. Subsequent aging treatment results in the precipitation of strengthening phases, γ′ (Ni3(Al,Ti)) and γ" (Ni3(Nb)), leading to significant improvements in hardness, compression plateau stress, and energy absorption value, which reach 518Hv, 520MPa, and 64J/g, respectively. These values are substantially higher compared to the sintered state. After the low-temperature (940℃) solid solution treatment, a significant amount of needle-like δ phase (Ni3(Nb)) is observed within the γ matrix. The microstructure consists of a γ matrix and δ phase (Ni3(Nb)). The corresponding hardness, compression plateau stress, and energy absorption value are 232Hv, 450MPa, and 66J/g, respectively. The hardness increases by approximately 6% compared to the 1020℃ (high-temperature) solid solution treatment due to the precipitation of the δ phase (Ni3(Nb)), which reduces the degree of matrix supersaturation. However, this also leads to a decreased amount of γ" strengthening phase during aging treatment. Consequently, the hardness, plateau stress, and energy absorption after aging treatment are 434Hv, 460MPa, and 70J/g, respectively, which are lower than those of the 1020℃ (high-temperature) solid solution and aging alloy but still significantly higher than the sintered state.
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