热等静压对第三代单晶高温合金微观组织和高温持久性能的影响

Effect of Hot Isostatic Pressing on the Microstructure and High Temperature Durability of Third-Generation Single-Crystal Superalloys

摘要:

以第三代单晶高温合金为研究对象，对比标准热处理和热等静压处理前后合金显微疏松和微观组织的变化，研究热等静压后不同温度固溶处理对微观组织演化规律及消除热等静压后γ′相粗化的影响，并在850 ℃/586 MPa和1120 ℃/140 MPa条件下进行持久性能测试。结果表明：与标准固溶热处理相比，经过热等静压处理后的合金共晶相全部溶解于基体中，合金中的缩孔完全闭合，枝晶干和枝晶间处的γ′相粗化长大；经过1280 ℃高温固溶处理后，枝晶干处粗大γ′相发生部分回溶，但是枝晶间存在大块状的γ′相；当固溶温度为1310 ℃时，枝晶干和枝晶间处的粗大γ′相完全回溶，并二次析出细小γ′相。对比持久性能发现：在850 ℃/586 MPa条件下，持久微裂纹主要源于MC碳化物，经热等静压处理后合金的持久寿命均略低于标准热处理样品；在1120 ℃/140 MPa变形过程中，枝晶干处的TCP相是主要裂纹源，热等静压后的样品持久性与标准热处理样品的相当。

Abstract:

In this paper， the effects of conventional heat treatment and hot isostatic pressing （HIP） on the micro-porosity and microstructure of third-generation singlecrystal superalloys were investigated. The microstructure evolution of the superalloy heat-treated at different temperatures after HIP was studied. The durability tests were carried out at 850 ℃/586 MPa and 1120 ℃/140 MPa respectively. The results show that compared with conventional heat treatment， the eutectics phase are completely dissolved into the matrix and pores in the alloy completely closed after HIP， with in the dendrite core and interdendritic region coarsening and growing. When further solution treated at 1280 ℃， the coarse in the dendrite core is partially re-dissolved， yet with large in the interdendritic region. While solution treated at 1310℃， the coarse γ′ in the dendrite core and interdendritic region is completely re-dissolved， and the fine re-precipitated. It can be found out from the durability tests that the permanent micro-cracks at 850 ℃/586 MPa are mainly caused by MC carbides， and that the creep rupture life of HIP treated alloys is slightly shorter than that of the conventionally heat-treated. However， during the deformation at 1120 ℃/140 MPa， the TCP phase in the dendrite core is the main source of cracks， and the properties of the samples after HIP were comparable to those of the conventionally heat-treated samples.