热处理对P、B微合金化GH4169合金组织与蠕变性能的影响

Influence of heat treatment regimes on microstructure and creep property of GH4169 alloy microalloyed by P,B

通过对锻造态GH4169合金进行短期时效处理、常规热处理和长期时效处理、蠕变性能测试及组织观察,研究了热处理制度对组织与蠕变性能的影响。结果表明:锻造态合金经短期时效处理、常规热处理及长期时效处理后,其组织结构由γ、γ'、γ"、针状δ-Ni_(3)Nb相和粒状(Nb,Ti)C、M_(23)C_(6)碳化物组成;其中,(Nb,Ti)C中富含P,而贫Cr、Mo。特别是短期时效处理合金的晶界无析出相,而长期时效处理合金中针状δ相沿晶界析出,随δ相数量及尺寸增加,合金中γ、γ'、γ"、相的晶格常数略有减小,各相间的错配度减小,但γ'/γ"两相间的错配度增加至δ_(γ'/γ")=0.233%;在长期时效态合金中,δ与γ相之间的晶体学关系为(200)_(γ)//(110)_(δ)和[011]_(γ)//[001]_(δ),其中,δ相的(020)_(δ)面与γ相的(111)_(γ)面、δ相的(110)_(δ)面与γ相的(111)面保持共格界面;与长期时效态合金相比较,时效处理态和常规热处理态合金有较好的蠕变抗力,其中,蠕变期间在长期时效态合金中的针状δ相处易产生应力集中,促使沿垂直于应力轴方向发生裂纹的萌生与扩展,可大幅度降低合金的蠕变寿命。

By means of short-term aged treated(STA),standard heat treated(ST),long-term aged treated(LTA)and microstructure observation,the effect of heat treatment regimes on microstructure of forged GH4169 alloy is investigated.The results show that after short-term aged treated,standard heat treated and long-term aged treated,the microstructure of forged GH4169 alloy consists ofγ,γ′,γ",needle-likeδ-Ni_(3)Nb phase and particle-like(Nb,Ti)C,M_(23)C_(6) carbides,therein,the P element is enriched in(Nb,Ti)C phase in which the elements Cr and Mo is poor.And after STA treated,no precipitated phases are identified in the boundary regions.After standard heat treated(ST)and long-term aged treated(LTA),there are needle-likeδphase precipitated along the grain boundaries,and the quantity and size of the one increase as the aged time prolongs.After LTA treated,the parameters ofγ、γ′andγ"phases in the alloy diminishes slightly,so that the misfits between the phases in alloy are diminished toδ_(γ/γ′)=0.361%andδ_(γ/γ")=0.128%respectively,and the misfit betweenγ′andγ"phases increases toδ_(γ'/γ")=0.233%.And after LTA treated,the crystallography relation between theδandγmatrix in the alloy is maintained to be(200)_(γ)//(110)_(δ)and[011]_(γ)//[001]_(δ),therein,the(020)_(δ),(110)_(δ)planes of needle-likeδ-Ni_(3)Nb phase and(111)_(γ),(111)planes ofγmatrix keep an coherent interface respectively.Compared to the LTA alloy,the STA and ST alloys display a better creep resistance.Therein,a large number of needle-likeδphase is precipitated in the LTA alloy along the boundary,which is easily to produce the stress concentration during creep,so that the cracks are easily initiated and propagated along the direction vertical to the stress axis.This is considered to be the main reason of the LTA alloy having a lower creep lifetime.