熱處理改良對單方向凝固鎳基高熵超合金之研究

Study on the Heat Treatment Improvement of Directionally Solidified High Entropy Ni-based Superalloy

顏柏充(Po-Chung Yen)

指導教授 ： 簡賸瑞

義守大學/理工學院/材料科學與工程學系/碩士(2016年)

摘要

本研究以鎳(Ni)作為基底，添加約十種不同元素並經由軟體計算後依照不
同比例添加，設計出三種不同比例的鎳基高熵超合金：HESA-A 只添加了
2wt.%的鉭而沒有鈮；而HESA-C 只添加了2wt.%的鈮而沒有鉭；HESA-B 則是鉭跟鈮各添加了1wt.%。透過不同熱處理溫度以及元素添加的變化，來探討其微觀組織及機械性質上的影響。研究發現，經過固溶熱處理1210℃後，強化相γ'已幾乎被溶回γ 基地中;而從不同溫度之時效熱處理的變化顯示，在900C 單時效及900C/750C 雙時效硬度值都超過了400HV，其中以900C/750C 雙時效的硬度值為最高，且其γ'體積分率亦為最高。而從合金設計元素添加的變化中發現，HESA-A 碳化物中的鉭含量高達48.81wt.%，HESA-B 碳化物中的鉭含量是27.82wt.%、鈮含量有20.81wt.%，HESA-C 碳化物中的鈮含量高達47.78 wt.%。從元素分佈分析探討γ´及γ 之間元素的含量變化得知，HESA-A因為添加了2wt.%的鉭，所以偏向γ´相的含量比HESA-B還要來的高，而HESA-C 因為添加了2wt.%的鈮，所以偏向γ´相的含量亦比HESA-B 還要來的高。另外，HESA-C 的鎢元素偏向在γ 基地相因為添加了鈮2wt.%但沒有添加鉭，而HESA-A 及HESA-B 的鎢元素卻仍然留在γ´相。

關鍵字

鎳基超合金 ； 高熵合金 ； 單方向凝固 ； 熱處理

並列摘要

In this study, nickel (Ni) as a base, by adding about ten elements and through software calculation, three kinds of nickel-based high-entropy superalloys were designed, namely, HESA-A only adds 2wt.% tantalum and no niobium, while HESA-C only adds 2wt.% of niobium and no tantalum, whereas HESA-B is added to each of tantalum and niobium with 1wt.%. Through different heat treatment temperatures and changes in the added element, microstructures are inspected and mechanical properties are investigated. The study found that after 1210C solution heat treatment, strengthening phase γ' has almost dissolved back to γbase phase, in addition hardness values exceed 400HV for both aging heat treatments at 900C single aging and 900C/750C double aging, where the hardness value of 900C/750C double aging is the highest one, nevertheless the γ' volume fraction of it is also the highest one. From the differences of added elements due to the alloy design of three nickel-based high-entropy superalloys, tantalum content of HESA-A carbides is 48.81wt.%, tantalum and niobium contents of HESA-B carbides are respectively 27.82wt.% and 20.81wt.%, niobium content of HESA-C carbides is 47.78 wt.%. From the partition analysis of element concentration between γ' and γ, because of adding 1wt.% more tantalum and no niobium, HESA-A shows higher content of tantalum in γ' phase than that of HESA-B, and HESA-C also shows higher content of niobium in γ' phase than that of HESA-B because of adding 1wt.% more niobium but no tantalum. Furthermore, tungsten in HESA-C moves to the γ base phase because of adding 2wt.% niobium but no tantalum, whereas tungsten remains in the γ' phase in both cases of HESA-A and HESA-B.

並列關鍵字

Directional solidification ； heat treatment ； superalloy ； high entropy alloy

參考文獻

[9] 葉均蔚，”高熵合金的發展”， 華岡工程，第27期，2011年，第1-18頁

[3] Bo Bai, Hongbo Guo, Hui Peng, Liquan Peng and Shengkai Gong, “Cyclic oxidation and interdiffusion behavior of a NiAlDy/RuNiAl coating on a Ni-based single crystal superalloy”, Corrosion Sci., vol. 53, 2011, pp. 2721–2727.

[4] An-Chou Yeh, Kang-Wei Lu, Chen-Ming Kuo, Hui-Yun Bor and Chao-Nan Wei, “Effect of serrated grain boundaries on the creep property of Inconel 718 superalloy”, Mater .Sci. Eng. A, vol. 530, 2011, pp. 525–529.

[5] D. K. Das, “Microstructure and high temperature oxidation behavior of Ptmodified aluminide bond coats on Ni-base superalloys”, Prog. Mat. Sci., vol. 58, 2013, pp. 151-182.

[6] M. Z. Alam, D. V. V. Satyanarayana, D. Chatterjee, R. Sarkar and D.K. Das, “Effect of prior cyclic oxidation on the creep behavior of directionally solidified(DS) CM-247LC alloy”, Mater. Sci. Eng. A, vol. 536, 2012, pp. 14– 23.