The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results sho...The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.展开更多
The effect of boron addition(0.010,0.015,and 0.020 wt.%)on the microstructure and mechanical properties of an additively manufactured superalloy was examined.The as-built microstructure was investigated by scanning el...The effect of boron addition(0.010,0.015,and 0.020 wt.%)on the microstructure and mechanical properties of an additively manufactured superalloy was examined.The as-built microstructure was investigated by scanning electron microscopy and transmission electron microscopy.The results demonstrate that boron precipitates as M_(3)B_(2)boride at the grain boundary.The increase in boron content increases the amount ofγ/γ′eutectic and the size and fraction of M_(3)B_(2)boride.Boron creates nanoscale fine borides at grain boundaries,which significantly reinforces grain boundaries.The mechanical property analysis indicated that the addition of boron improved the tensile ductility at 760℃and stress rupture properties at 760℃/780 MPa.However,with the excessive addition of boron,the mechanical property was reduced.展开更多
基金supported financially by the National Natural Science Foundation of China (Nos. 11332010,51671189 and 51701210)the Project from China Huaneng Group Co. Ltd. (No. ZD-15-HJK02)
文摘The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.
基金The authors are grateful for the financial support provided by the National Key Research and Development Program of China(No.2021YFB3702500)National Science and Technology Major Project of China(Y2019-VII-0011-0151,2019-VII-0019-0161).
文摘The effect of boron addition(0.010,0.015,and 0.020 wt.%)on the microstructure and mechanical properties of an additively manufactured superalloy was examined.The as-built microstructure was investigated by scanning electron microscopy and transmission electron microscopy.The results demonstrate that boron precipitates as M_(3)B_(2)boride at the grain boundary.The increase in boron content increases the amount ofγ/γ′eutectic and the size and fraction of M_(3)B_(2)boride.Boron creates nanoscale fine borides at grain boundaries,which significantly reinforces grain boundaries.The mechanical property analysis indicated that the addition of boron improved the tensile ductility at 760℃and stress rupture properties at 760℃/780 MPa.However,with the excessive addition of boron,the mechanical property was reduced.
