浇注温度和细化剂对K4169高温合金微观组织的影响

研究了降低浇注温度或加入细化剂后 ,K4 16 9合金晶粒细化的微观组织、夹杂及缩松等的变化。发现同样加或不加细化剂条件下 ,浇注温度越低 ,一次枝晶主轴长度和二次枝晶臂距越小。而同一浇注温度下 ,化学法细晶试样一次枝晶主轴长度较普通试样的短 ,而二者的二次枝晶臂距无明显差别。晶粒细化后 ,晶粒形态由普通铸造组织中的树枝晶向细晶组织中的粒状晶转变 ,且合金中主要元素的偏析减轻 ,这均有利于提高细晶铸件机械性能。MC型碳化物和Laves相的尺寸、数量和形貌在晶粒细化前后变化不大。铸件中加入微量细化剂不形成夹杂 ,不改变合金相组成。此外 ,加细化剂不仅可使晶粒细化 ,同时铸件中的缩松大大减少

Effects of pouring temperature and refiners on microstructures of superalloy K4169

In the present study, the effects of pouring temperature and refiners on dendrite structures, interdendritic segregation, precipitates, inclusion and microporosity of cast superalloy K4169 were investigated. It is found that the higher the pouring temperature, the greater the length of the average primary dendrite axes (l axes ) and the secondary dendrite arm spacing (SDAS). At the same pouring temperature, l axes was shortened with the addition of refiner. However, SDAS kept almost unchanged. Additionally, the morphology of grains was transformed from dendrite in conventionally cast castings to granulation in fine grained castings and the segregation ratios of main elements were alleviated with the decrease of grain size, which are beneficial for the improvement in mechanical properties. The size, amount and morphologies of MC type carbides and Laves phase had no remarkable change after grain refinement.Moreover, it is also found that trace addition of refiner to the melt did not bring in inclusion and change the phase constitution of the alloy. The amount of microporosity in samples with the addition of refiner can be greatly decreased.