固溶冷却速度和前处理对新型镍基粉末高温合金组织与显微硬度的影响

Effect of Solution Cooling Rate and Pre-heat Treatment on the Microstructure and Microhardness of a Novel Type Nickel-Based P/M Superalloy

摘要:

对新型镍基粉末高温合金FGH98Ⅰ分别进行亚固溶前处理+过固溶和过固溶热处理，利用光学显微镜，场发射扫描电镜和显微硬度仪研究冷却速度对合金组织与显微硬度的影响。结果表明：过固溶处理前的亚固溶前处理使锻态合金中大晶界γ′相发生部分溶解，晶粒稍有长大，对过固溶热处理冷却γ′相析出的影响不显著；随着冷速增加，合金中二次和三次γ′相的尺寸减小，二次γ′相的形状从蝶形向球形转变，γ′相的颗粒密度增大，面积分数减小，在冷却速度≤1.4 ℃/s时，γ′相分两阶段形核；冷速越快，合金的硬度越高，时效后硬度增高越多。另外，还建立了冷速与γ′相平均尺寸和合金硬度之间的函数关系式。该结果为FGH98Ⅰ合金实际双性能盘固溶热处理工艺的选择提供了理论参考

Abstract:

The effect of solution cooling rate on the microstructure and microhardness of a novel type nickel-based P/M superalloy FGH98Ⅰin subslovus plus superslovus and superslovus heat treatment condition was studied by means of optical microscope (OM), field emission scanning electron microscope (FESEM) and microhardness tester. The results show that subslovus pre-heat treatment makes the large grain boundary γ ' phase of as-forged alloy partial dissolution, and the grains grow a little, while the influence on the cooling γ ' precipitates of superslovus heat treatment is not obvious. The average sizes of secondary and tertiary γ ' precipitates decrease with the cooling rate increasing. Meanwhile, the shape of secondary γ ' precipitates changes from the butterfly-like to the spherical, the γ ' phase particle density increases and the area fraction decreases. It is also found that γ ' phases nucleate and precipitate in two stages if the cooling rate is not faster than 1.4 °C/s. The higher the cooling rate, the higher the microhardness, and the microhardness increases more after aging. In addition, the average sizes of γ′ precipitates and the microhardness as a function of cooling rate are established. The above results can be used as a theoretical reference for the selection of actual superslovus processing of FGH98Ⅰdual-property disk