980℃长期时效对DD15单晶高温合金组织稳定性的影响

Effect of Long Term Aging at 980℃on Microstructure Stability of DD15 Single Crystal Superalloy

采用选晶法在真空高梯度定向凝固炉中制备第四代单晶高温合金DD15试棒,热处理后在980℃分别时效400、800、1200、1600、2000 h,研究不同时效时间的合金组织。结果表明:合金的热处理组织由立方化较好γ′相和基体γ相组成。随着980℃时效时间增加,γ′相合并长大仍保持立方形状,基体通道的宽度增加;时效1600 h时,未有TCP相析出;时效2000 h时,析出极少量TCP相,合金具有良好的组织稳定性;合金中较多的Re、W、Ta、Mo、Nb等高熔点元素能够抑制γ′相长大,Ru元素能够抑制TCP相的析出,合金具有良好的组织稳定性。

The fourth generation single crystal superalloy DD15 rods were prepared by screw selecting method in a directionally solidified furnace.The long term aging of the alloy after full heat treatment was performed at 980℃for 400 h,800 h,1200 h,1600 h and 2000 h,respectively.The microstructure evolution of the alloy after long term aging for different times was investigated.The results show that the alloy consists of the regular cubicγ′phase andγphase after full heat treatment.The size ofγ′phase increases,but still in cubic shape,and the space ofγmatrix channel increases with the increase of long term aging time.No TCP phase can be observed after long term aging for 1600 h.A little needle shaped TCP phase were observed after long term aging for 2000 h.Higher additions of refractory alloying elements Re,W,Ta,Mo and Nb in the alloy can suppressγ′phase growing up and Ru can make the alloy more resistant to the formation of TCP phases.Therefore,the alloy has very excellent microstructure stability.