微量元素对定向凝固高温合金DZ125微观组织和力学性能的影响

Effects of minor elements on microstructure and mechanical properties of directionally solidified superalloy DZ125

定向凝固高温合金DZ125是我国现役主力航空发动机涡轮叶片材料,本工作研究Si、S、Zr等微量元素对DZ125合金微观组织和力学性能的影响。结果表明,S在DZ125合金中主要以M2SC的形式和MC共生,同时在碳化物和晶界富集;Si主要在晶界碳化物中富集;当合金中Zr含量达到0.044%(质量分数)时,M2SC化合物中还含有约6%的Zr。在所研究的含量范围内,Si、S、Zr等微量元素对DZ125合金的室温拉伸性能没有明显影响,但对持久性能有一定影响,当Si、S、Zr含量升高到较高水平,合金的760℃/804 MPa持久寿命明显下降,980℃/235 MPa持久寿命持续缓慢下降,这与Si、S、Zr含量升高所导致的M2SC相析出,Si、S在碳化物和晶界的富集,以及枝晶干区γ′相立方化程度下降等微观组织变化有关。为了保证DZ125合金具有良好的力学性能,Si、S、Zr等微量元素含量应控制在较低水平。

The effects of Si,S and Zr on the microstructure and mechanical properties of directionally solidified superalloy DZ125 were studied.The results showed that S formed M2SC compound growing with MC carbides together in DZ125 alloy,and S was also rich in carbides and grain boundary.Si mainly distributed in carbides in grain boundary.When Zr content in DZ125 alloy is up to 0.044%(mass fraction),Zr participated the formation of M2SC,which have about 6%Zr.In the scope of research,Si,S and Zr hadn’t obvious effect on the tensile properties at room temperature of DZ125 alloy.However,they had harmful influence on the stress rupture properties,when their content in the alloy increased to some high level,the stress rupture lives under 760℃/804 MPa were degraded about 50%.And the stress rupture lives under 980℃/235 MPa decreased slowly with the content of Si,S and Zr.The deterioration of stress rupture properties was due to the formation of M2SC,the enrichment of S and Si in carbides and grain boundary,as well as the decline of cuboidal content ofγ'phase in the dendrite regions.Therefore,the content of Si,S and Zr should be kept to low level relatively,in order to ensure DZ125 alloy have good mechanical properties.