不同熱處理溫度條件對單方向凝固CM-681LC鎳基超合金之微結構及高溫潛變之影響

Effects of Different Heat Treatment Temperatures on Microstructure and High-Temperature Creep of Directionally Solidified CM-681LC Ni-Based Superalloy

張芷旖(Jhih-Yi Jhang)

指導教授 ： 簡賸瑞

共同指導教授 ： 郭振明(Chen-Ming Kuo)

義守大學/理工學院/材料科學與工程學系/碩士(2017年)

摘要

本研究採用CM-681LC鎳基超合金為材料基礎。一開始先將試棒進行單方向凝固製程，條件為：180mm/hr、溫度1550℃，使試棒鑄造成為單方向晶的試棒。而後使用不同的熱處理製程進行實驗，本研究有兩種熱處理條件，其一是規範所給的條件，為HT1；另一為使用示差掃描量熱儀(Differential Scanning Calorimetry，DSC)所取的條件，為HT2。HT1：固溶溫度1185℃/4hr/ArC，搭配第一次時效1038℃/2hr和第二次時效870℃/20hr/ArC；HT2：固溶溫度1270℃/4hr/ArC，搭配第一次時效1038℃/2hr和第二次時效870℃/20hr/ArC，只有固溶熱處溫度不同，第一次時效熱處理以及第二次時效熱處理是相同的。探討兩者之間微結構的不同與高溫潛變的不同。本實驗透過掃描式電子顯微鏡(Scanning Electron Microscopy， SEM)、能量散射光譜儀(Energy Dispersive Spectrometer，EDS)和穿透式電子顯微鏡(Translation Electron Microscopy，TEM)等方式進行微觀組織的觀察。機械性質潛變測試之測試條件為1050℃/200MPa，屬於超高溫低應力之潛變測試。研究結果顯示，HT2因為其γˊ相因為熱處理程序較佳，使得γˊ相體積分率比HT1大與γ channel寬度也比HT1窄，因此潛變測試過程中差排不易移動，使CM-681 LC的機械性質增加。

關鍵字

CM-681 LC鎳基超合金 ； 單方向凝固 ； 熱處理 ； 高溫潛變 ； 差排

並列摘要

In this study, CM-681LC nickel-based superalloy was selected as the base material with two solution heat treatment temperatures, HT1: 1185℃ for 4hr with Argon cooling to the ambient temperature, which is according to the Cannon-Muskegon Co. Technical Bulletin; HT2: 1270℃ for 4hr with Argon cooling, which is based upon Differential Scanning Calorimetry results. The aging heat treatment has two steps; the first aging is at 1038℃ for 2hr with Argon cooling followed by the second aging temperature at 870℃ for 20hr with Argon cooling. Directionally solidified round bar specimens were produced by typical Bridgeman type casting furnace. Microscopic observations were carried out by Scanning Electron Microscopy with Energy Dispersive Spectrometer and Transmitted Microscopy. Creep tests at 1050℃ and 200MPa were conducted by ATS level arm creep tester. Creep rupture life of HT1 and HT2 is 43 and 64 hours, respectively. Since HT2 produces uniformly distributed cuboidal γ' precipitates with 0.29 µm average size and 84.5% volume fraction, the γ channel width is 9.15 nm, which is narrower than that of HT1 10.26 nm. Uniformly distributed γ′ precipitates and narrower γ channel width could result in higher Orowan bowing shear stress, which might have efficiently stuck the dislocation motions across the precipitates; consequently, creep rupture life of HT2 is 21 hours overrun at the ultra-high temperature regime.

並列關鍵字

CM-681LC superalloy ； directionally solidification ； heat treatment ； creep ； dislocation

參考文獻

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