长期时效对FGH96粉末高温合金组织稳定性及性能的影响

Effect of long-term aging on microstructure stability and properties of FGH96 P/M superalloy

研究了FGH96粉末高温合金经750℃长期时效1000和3000 h后的晶粒尺寸、晶界形貌、晶粒取向、γ′强化相和碳化物的演变规律及长期时效对合金650℃使用温度下拉伸性能的影响。结果表明:750℃长期时效对合金的晶粒尺寸、晶界形貌和晶粒取向没有明显影响。然而,长期时效后,合金中γ′相形貌、尺寸和分布发生了显著的变化,大尺寸γ′相先长大后分裂再变小,平均尺寸变大、尺寸梯度降低、间距变大,由双峰分布最终演变为单峰分布;形貌由近球形、方状和蝶状先演变为不规则状,最终又演变回近球状、方状与蝶状。未长期时效合金的晶内和晶界处存在大量富含Ti、Nb元素的块状MC型的碳化物,并与MB型硼化物共存,经750℃长期时效3000 h后没有明显变化。而富含Cr元素的M_(23)C_(6)型小颗粒碳化物经750℃长期时效3000 h后,析出量增加并呈链状分布于晶界。长期时效后,FGH96合金650℃拉伸强度降低,塑性提高,主要原因是合金中的γ′相分裂、粗化及晶界处M_(23)C_(6)型碳化物析出呈链状分布所致。

The evolution of grain size,grain boundary morphology,grain orientation,γ′strengthening phase and carbides of FGH96 P/M superalloy after long-term aging at 750℃ for 1000 h and 3000 h was studied,and the effect of long-term aging on tensile properties of the FGH96 superalloy at 650℃ was also studied.The results show that the long-term aging at 750℃ has no significant effect on the grain size,grain boundary morphology and grain orientation of the alloy.However,after long-term aging,the morphology,size and distribution of γ′phase of the alloy change significantly,and the size of the lager-scale γ′phase grows first,then spits and decreases,the average size increases,the size gradient decreases,the spacing distance increases,and the bimodal distribution finally evolves into the unimodal distribution.The morphology of the lager-scale γ′phase first changes from near spherical,square and butterfly shape to irregular shape,and then changes from irregular shape to near spherical,square and butterfly shape again.There are a lot of bulk MC type carbides rich in Ti and Nb elements inside and at the grain boundaries of the alloy without long-term aging,and coexist with MB boride.After aging at 750℃ for 3000 h,there is no obvious change.The precipitation amount of M_(23)C_(6) type carbides rich in Cr element increases after longterm aging at 750℃ for 3000 h,and distributes in chain shape at the grain boundary.After long-term aging,the tensile strength and plasticity of the FGH96 alloy at 650℃ decrease,which is mainly due to the γ′phase splitting,coarsening and M_(23)C_(6) carbides precipitation at the grain boundary with chain like distribution.