固溶热处理对新型镍基粉末FGH98Ⅰ高温合金组织与性能的影响

Effect of Solution Heat Treatment on the Microstructure and Properties of a Novel Nickel-Based P/M Superalloy FGH98 I

摘要:

对新型镍基粉末高温合金 (FGH98Ⅰ)在不同温度下进行固溶热处理, 采用热力学相计算、光学显微镜、场发射扫描电镜及化学相分析等研究了亚固溶和过固溶合金的析出相和显微组织，并综合分析了组织与性能的关系。结果表明: FGH98Ⅰ合金经1130 ℃亚固溶和1190 ℃过固溶处理后的析出相均为γ＇、MC、M23C6和M3B2等，未发现TCP(拓扑密堆)相。FGH98Ⅰ合金亚固溶热处理后晶粒稍有长大，存在尺寸不同的初次、二次和三次γ′相；过固溶热处理合金的晶粒明显长大，存在单模分布的二次γ′相；前者由于晶粒较小使强度更高，后者因减小二次γ′相尺寸和消除初次γ′相，PPB(原始颗粒边界)和残余枝晶，提高了合金的高温塑性和持久性能，说明不同晶粒尺寸和γ′相特征是FGH98Ⅰ盘件获得双性能的关键因素

Abstract:

The microstructure and precipitates of a novel nickel-based powder metallurgy (P/M) superalloy FGH98 I in subsolvus and supersolvus heat treatment condition was studied by means of thermodynamic calculation, OM, FESEM and chemical phase analysis. The relationship between microstructure and mechanical properties was also analyzed. The results show that the precipitates of the alloy FGH98 I heat treated at 1130 oC and 1190 oC are γ′, MC, M23C6 and M3B2, without the observation of TCP phases. The grains of subsolvus heat treated FGH98 I grow slightly, and there are primary, secondary and tertiary γ′ phases with different sizes. The grains of supersolvus heat treated FGH98 I grow significantly, and the alloy has monomodal γ′ precipitate distribution. The former has higher strength because of finer grains, while the latter has improved high temperature ductility and stress rupture properties due to the reduced size of secondary γ′ phases and the elimination of primary γ′ phases, PPB (prior particle boundary) and residual dendrite structure. It reveals that the different grain sizes and γ′ characteristics are the key factors for dual-property FGH98 I disk