固溶时效处理工艺对一种四代镍基单晶高温合金组织、性能的影响

Effect of Solution and Aging heat treatment on Microstructures and Stress Rupture properties of a 4-th generation Ni-based Single Crystal Superalloy

摘要:

研究了固溶时效处理对一研制的Re、Ru含量分别为4.0%(质量分数)的第四代镍基单晶高温合金DD476的组织及持久性能的影响。铸态试样存在明显的成分偏析,由于Al、Ti元素较少,枝晶间的γ/γ’共晶组织含量偏低。固溶处理过程中,共晶组织在1310℃下基本消除,但直到1340℃才完全消除枝晶干和枝晶间的差异且此时除了Re其他元素偏析有明显的改善。四代单晶的优势在于提高了合金在高温下的力学性能尤其是持久性能,固溶时效后单晶合金在950℃/300MPa下持久寿命约为二代单晶的两倍,而在1150℃/100MPa下持久寿命与二代单晶MC2相比更是提高了10倍以上。整个固溶时效处理过程中没有出现TCP相,合金中Ru元素的添加可能是抑制TCP相析出的主要原因。

Abstract:

Effect of solution and aging heat treatment on microstructures and stress rupture properties of a fourth generation Ni-based single crystal superalloy with content of 4.0% (in weight percent) Re and Ru has been investigated.The results show that the as-cast alloy exists significant composition segregation.Due to less Al and Ti elements, interdendritic γ/γ’ eutectic content is low.During the solution heat treatment,the eutectic is almost dissolution after 1310℃.However,the differences between dendrite core and interdendritic is completely eliminated until 1340℃ and the segregation of other elements except Re is significantly improved.The advantage of the fourth generation Ni-based single crystal is to improve the mechanical propertie at high temperature,especially stress rupture properties.After solution and aging heat treatment,the stress rupture lives of DD476 is about twice that of the second generation single crystal superalloy at 950℃/300MPa and is more than 10 times comparaed with the second generation single crystal superalloy MC2 at 1150℃/100MPa.There is no TCP(topologically close-packed) precipitation during the whole heat treatment because of the addition of Ru element in DD476.