Microstructure evolution and stress rupture properties of K4750 alloys with various B contents during long-term aging
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2021年第14期
论文作者：Xiaoxiao Li Meiqiong Ou Min Wang Xiangdong Zha Yingche Ma Kui Liu
摘 要：The relationship among B content,microstructure evolution and stress rupture properties of K4750 alloy during long-term aging were investigated.After aging at 800℃ for 1000 h,the decomposition degree of MC carbides of K4750 alloys with 0 B,0.007 wt.% B and 0.010 wt.% B were basically identical,which indicated that B has no inhibition on MC carbide decomposition during long-term aging.The MC carbide decomposition was accompanied by the formation of M23C6 carbides and a small number of η phases,which was controlled by the outward diffusion of C and Ti combined with the inward diffusion of Ni and Cr from the γ matrix.In addition,M23C6 carbides in boron-free alloy were in continuous chain and needle-like η phases were precipitated near them,while M23C6 carbides in boron-containing alloys remained in granular distribution and no η phases precipitation around them.Adding B could delay the agglomeration and coarsening of M23C6 carbides during long-term aging,which was because the segregation of B at grain boundary retarded the diffusion of alloy elements,thus weakened the local fluctuation of chemical composition near grain boundary.The stress rupture samples of K4750 alloys with various B contents after aging at 800℃ for 1000 h were tested at 750℃/380 MPa.The results indicated that the stress rupture properties of bo ron-containing alloys were significantly better than that of boron-free alloy,which could be attributed to the increase of grain boundary cohesion strength and the optimization of M23C6 carbide distribution due to the addition of B.
Xiaoxiao Li1,2，Meiqiong Ou1，Min Wang1，Xiangdong Zha1，Yingche Ma1，Kui Liu1
1. Institute of Metal Research, Chinese Academy of Sciences2. School of Materials Science and Engineering, University of Science and Technology of China
摘 要：The relationship among B content,microstructure evolution and stress rupture properties of K4750 alloy during long-term aging were investigated.After aging at 800℃ for 1000 h,the decomposition degree of MC carbides of K4750 alloys with 0 B,0.007 wt.% B and 0.010 wt.% B were basically identical,which indicated that B has no inhibition on MC carbide decomposition during long-term aging.The MC carbide decomposition was accompanied by the formation of M23C6 carbides and a small number of η phases,which was controlled by the outward diffusion of C and Ti combined with the inward diffusion of Ni and Cr from the γ matrix.In addition,M23C6 carbides in boron-free alloy were in continuous chain and needle-like η phases were precipitated near them,while M23C6 carbides in boron-containing alloys remained in granular distribution and no η phases precipitation around them.Adding B could delay the agglomeration and coarsening of M23C6 carbides during long-term aging,which was because the segregation of B at grain boundary retarded the diffusion of alloy elements,thus weakened the local fluctuation of chemical composition near grain boundary.The stress rupture samples of K4750 alloys with various B contents after aging at 800℃ for 1000 h were tested at 750℃/380 MPa.The results indicated that the stress rupture properties of bo ron-containing alloys were significantly better than that of boron-free alloy,which could be attributed to the increase of grain boundary cohesion strength and the optimization of M23C6 carbide distribution due to the addition of B.
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