固溶强化型镍基合金的时效析出行为

为了给700 ℃超超临界机组选材提供技术参考,研究了2种固溶强化型镍基合金（617和625）经时效处理（时效）后的析出行为。结果表明：2种镍基合金760 ℃时效后,均析出M₂₃C₆、M₆C碳化物和γ′相;M₂₃C₆、M₆C碳化物分布于晶界和晶内,γ′相分布于晶内;γ″相在625合金晶界、层错处析出并向晶内生长。617合金时效3 000 h,晶界析出相不连续分布;时效5 000 h后晶界析出相聚集且连续分布,晶内析出相的尺寸基本稳定。625合金时效3 000 h的晶内析出相尺寸无明显变化,晶界M₂₃C₆颗粒聚集长大;时效5 000 h后M₂₃C₆转变为M₆C碳化物。617合金和625合金时效后的冲击吸收能量均明显下降,时效后的625合金脆化程度较时效后的617合金严重。

Aging Precipitation Behavior of Solid-Solution Strengthened Nickel-Base Alloys

Aging precipitation behavior of the two solid-solution strengthened Ni-based alloys(617 and 625) has been investigated. The results revealed that the M₂₃C₆ and M₆C carbide particles precipitated both at the grain boundaries and inside grains, and the γ phase particles were situated at intragranular sites in the process of aging at 760 ℃ for two alloys. In addition, γ″ phase precipitated at grain boundaries and stacking faults in the aged alloy 625. The carbide particles discontinuously dispersed at grain boundaries after aging for up to 3 000 h for alloy 617; however, the 5 000 h aging induced the coalescence of the carbide particles. After aging up to 5 000 h, the size of precipitates inside grains remained basically stable for alloy 617. The carbides precipitates dispersed continuously at inter-granular site were observed in the alloy 625 aged for 3 000 h and an increase of aging time resulted in the growth of carbide particles. The size of intragranular particles kept almost unchanged after aging for up to 3 000 h for alloy 625; however, the presence of a number of M₆C particles was visible for alloy 625 after 5 000 h. The impact absorbed energy obviously declined for two alloys after aging. Aging embrittlement of the alloy 625 is greater than that of the alloy 617.