热等静压处理对K439B高温合金显微组织的影响

对K439B合金进行了1165 ℃/150 MPa,4 h热等静压处理,采用光学显微镜和扫描电镜对比研究了铸态和热等静压态K439B合金的显微组织。结果表明:铸态K439B合金存在0.25%的显微疏松,热等静压后显微疏松基本消除(0.013%)。与铸态相比,经过热等静压处理后合金中的γ/γ′共晶组织体积分数和尺寸减小,各元素分布更加均匀,凝固偏析系数均更接近1。铸态K439B合金枝晶干处γ′相尺寸和体积分数分别是116.9 nm和17.8%,枝晶间部位γ′相尺寸和体积分数分别为244.4 nm和24.9%。热等静压后合金枝晶干部位的γ′相尺寸及体积分数分别为148.0 nm和17.5%,枝晶间部位γ′相尺寸和体积分数分别为159.1 nm和22.8%。热等静压处理使合金枝晶干、枝晶间部位的γ′相尺寸、体积分数和形貌接近,同时γ′相分布变得均匀。

Effect of hot isostatic pressing on microstructure of K439B superalloy

K439B superalloy was hot isostatic pressed (HIP) under 1165 ℃/150 MPa for 4 h, then the microstructure of as-cast and hot isostatic pressed K439B alloy was investigated comparatively by using OM and SEM. The results show that the as-cast K439B alloy has microporosity of 0.25%, which is reduced down to only 0.013% after HIP. Compared with the as-cast microstructure, after HIP both the content and the size of γ/γ′ eutectic decrease, and all the elements are distributed more evenly, with their solidification segregation coefficients being closer to 1. The size and volume fraction of γ′ precipitates in the dendritic arms of as-cast K439B alloy are 116.9 nm and 17.8% respectively, and that in interdendritic region are 244.4 nm and 24.9%. After HIP, the size and volume fraction of γ′ precipitates in the dendritic arms are 148.0 nm and 17.5% respectively, and that in the interdendritic region are 159.1 nm and 22.8%. The hot isostatic pressing makes that the size, volume fraction and morphology of γ′ precipitates in the dendritic arms in the alloy and that in the interdendritic region become more similar to each other, and the γ′ precipitates distribute more uniformly.