FGH97合金连续冷却过程中的γ′相析出行为

Investigation on the precipitation behavior of γ′ in superalloy FGH97 during continuous cooling from supersolvus temperature

摘要:

为了研究固溶冷却速度对粉末高温合金FGH97的γ′相析出行为,利用Gleeble-3800热模拟试验机以及模拟热处理炉获得了15~240°C/min的冷却速度,主要分析了不同冷却速度对二次γ′相尺寸、形貌以及力学性能的影响。研究发现,二次γ′相在冷却过程中发生析出、长大,甚至是粗化,并且其形貌、尺寸以及析出温度、析出范围主要取决于冷却速度,而时效处理几乎没有影响。在15°C/min的较低冷速下,二次γ′相发生粗化并分裂,形成0.38μm左右的方形颗粒,这些二次相周围还会析出三次γ′相；而当冷却速度达到60°C/min时,二次γ′相尺寸降至0.22μm左右,三次γ′相析出则被完全抑制。在析出相含量、尺寸以及γ/γ′错配度的共同作用下,合金强度随着冷却速度的增加呈现出先降低后升高的趋势。

Abstract:

This paper presents results from a research initiative aimed at the γ′ precipitation behavior in superalloy FGH97 during continuous cooling from supersolvus temperature by Gleeble-3800 and heat treatment simulator furnace at cooling rates of 15~240 °C/min. The influence of cooling rates on γ′ size, paticle morphology and tensile strength is investigated. During cooling from supersolvus temperature γ′ nucleation and growth, even coarsening, simultaneously occur. However, ageing treatment seems to exert little influence on γ′ evolution. At the cooling rate of 15 °C/min a large number of secondary γ′ split and form square paticles with ~0.38 μm. Meanwhile, there are lots of small tertiary spherical γ′ around secondary γ′. As the cooling rate decreasing to 60 °C/min the size of secondary γ′ decreases to ~ 0.22 μm and the precipitation of tertiary γ′ is completely inhibited. The tensile strength tends to increase after an initial decrease with a decline of cooling rates, due to the combined influence of γ′ volume fraction, particle size and γ/γ′ mismatch.