热等静压工艺对K4125镍基高温合金显微组织的影响

采用3组不同参数的热等静压(HIP)工艺对K4125镍基高温合金进行显微组织演变研究。结果表明,3种热等静压工艺制备的合金中Hf、Mo等在MC碳化物中的分布区域略有不同,Ta、Mo、Co、Cr、Ti及Al等为正偏析元素,W、Ni为负偏析元素,与其他元素相比较,Ni、Co、Cr偏析程度较小,提高热等静压温度及压力,各元素的偏析程度均有所降低,γ/γ′共晶组织含量逐渐减少,同时枝晶干γ′相的尺寸显著降低,但面积分数无明显变化。此外,3种热等静压合金均出现大块状MC碳化物碎化、二次MC碳化物析出及晶界细小碳化物形成等现象,提高热等静压温度及压力后,这种现象加剧,且碳化物中Ta、Ti含量降低,TaC、TiC的分解倾向增加。

Effect of hot isostatic pressing on microstructure of nickel-based superalloy K4125

Microstructure evolution of nickel-based superalloy K4125 was studied by hot isostatic pressing (HIP) with three different sets of parameters. The results show that the distribution areas of Hf, Mo and other elements in MC carbide are slightly different in the alloys prepared by three HIP. Ta, Mo, Co, Cr, Ti and Al are positive segregation elements, while W and Ni are negative segregation elements. Compared with other elements, the segregation degree of Ni, Co and Cr is smaller, and with the increase of HIP temperature and pressure, the segregation degree of all elements decreases, and the content of γ/γ′ eutectic decreases gradually. Meanwhile, the size of γ′ phase decreases significantly while its area fraction has no obvious change. In addition, the fragmentation of massive MC carbides, the precipitation of secondary MC carbides and the appearance of fine carbides at grain boundaries are observed in all the three HIP alloys. This phenomenon is intensified when the temperature and pressure are increased, and the contents of Ta and Ti in carbides decrease, while the decomposition tendency of TaC and TiC increases.