反覆銲接與熱處理對Inconel 718鎳基超合金機械性質之研究

Inconel-718鎳基超合金擁有良好的高溫強度、耐高溫腐蝕等優異性質，並可提供優良的鑄造性、加工性及銲接性。使用Inconel 718製作航太結構體及零組件，當工件完成時，原材會經過反覆熱處理，而銲道會經過鏟修、反覆銲接與熱處理之製程。本研究在於建立不同熱處理條件及反覆銲接與熱處理之製程，對於718合金原材及銲接處之顯微結構與機械性質之影響，並探討其破壞原因是否與原材受到反覆熱處理或是反覆銲接之製程有關。實驗結果顯示，對於母材而言，980℃固溶與720/620℃雙時效處理，可得到最高之常溫拉伸強度，但是衝擊韌性相當差，且反覆熱處理之製程會使強度大幅變化；1065℃固溶與760/650℃雙時效熱處理則有較好之強度、伸長率與韌性之組合。並且發現因為鏟修銲道而多進行一次固溶處理對於原材之機械性質並不會有顯著影響。對於銲件而言不論使用980℃或是1065℃之固溶溫度，都無法完全將Laves相消除，因而造成銲件之衝擊韌性較差，使得經過銲後熱處理後之材料，破斷處均發生在銲道。但是經過銲後熱處理後以980℃固溶與720/620℃雙時效熱處理後之試片常溫強度大幅提高，但是高溫強度則是以1065℃固溶與760/650℃雙時效熱處理效果最好。同時可以發現，反覆銲接之製程對於銲件之機械性質沒有顯著影響，此並非造成銲件解體或破壞之主要原因。若在實際之高溫環境（704℃）下使用，銲後進行1065℃固溶→720℃、620℃雙時效處理或銲後進行1065℃固溶→760℃、650℃雙時效處理所得之機械性質較佳，銲後進行1065℃固溶→720℃、620℃雙時效處理有較高之強度而銲後進行1065℃固溶→760℃、650℃雙時效處理有較好的伸長率，因此可依實際使用之需求來選擇適當之銲後熱處理條件。

關鍵字

氬銲；鎳基超合金；熱處理；顯微結構

並列摘要

The Inconel 718, a nickel-based superalloy with its high strength and high corrosion resistance at elevated temperature, becomes a popular superalloy for high temperature application in the past decades. It has good castability, workability, and weldability. Therefore, Inconel 718 has been widely used to produce aero-parts and as structural material. In practical manufacturing, the base metal and welded parts must conduct cyclic heat treatments and repeat welding, respectively. The effects of a series of different and cyclic heat treatments after the welding processes on the microstructure and mechanical properties of 718 alloy have been throughly investigated in this study. Experimental results show that the base metal conducting the solid solution treatment at 980℃ and double ageing-treatment at 720/620℃ would have the highest tensile strength at room temperature. However, this heat-treatment would significantly change the strength and deteriorate the impact toughness of the weldment. Additionally, the solid solution treatment at 1065℃ and double ageing treatment at 760/650℃ would enhance the strength, elongation, and toughness of the weldment. Because solid solution treatment at 980℃ and 1065℃ can not dissolve all the Laves phase in the weld pool, the weldments have low impact toughness. After post weld heat treatment, the weldments would fracture in the area of weld pool. Weldments would have the highest tensile strength at room temperature after solid solution treatment at 980℃ and double ageing treatment at 720/620℃. Additionally, after the solid solution treatment at 1065℃ and double ageing treatment at 760/650℃, the weldments would have the highest high-temperature tensile strength. According to the similar results of mechanical test, the repeated welding is not the primary reason causing the fracture. The weldments conducting post weld heat treatments of H8 (solid solution treatment at 1065℃ and double ageing treatment at 720/620℃) and H9 (solid solution treatment at 1065℃ and double ageing treatment at 760/650℃) have better mechanical properties at 704℃. Procedure of both post weld heat treatments are recommended since the weldments conducted heat treatment of H8 and H9 have better strength and elongation, respectively. The opportunity of heat treatments depends on the actual situation.

並列關鍵字

TIG ； GTAW ； superalloy ； Inconel 718 ； heat treatment ； microstructure

參考文獻

M.G. Burke and M.K. Miller*, “Precipitation In Alloy 718: A Combined AEM and APFIM Investigation”, Superalloys 718, 625 and Various Derivatives Edited by E.A. Loria, TMS, 1991, p.337.

E.F. Wachtel and H.J. Rack, "Phase Stability and Aging Response of TiC Reinforced Alloy 718", Superalloy 718-Metallurgy and Applications Edited by E.A. Loria, TMS, 1989, p.599.

W.F. Smith, “Structure and Properties od Engineering Alloys”, 1981, McGraw-Hill, p.519.

R. Cozar and A. Pineau, "Morphology of γ' and γ" Precipitates and Thermal Stability of Inconel 718 Type Alloys", Metall. Trans., Vol 4A, 1, 1973, p.77.

S. Azadian, L.Y. Wei, R. Warren, "Delta Phase Precipitation in Inconel-718", Materials Characterization, 53, 2004, p.7.

國際替代計量

反覆銲接與熱處理對Inconel 718鎳基超合金機械性質之研究

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