Guichen HOU
材料科学技术（英）
The oxidation behavior of a cast polycrystalline Co-base superalloy was studied at temperatures from 900 to 1050℃ and analyzed by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that a cast Co-base superalloy follows the subparabolic oxidation kinetics at 900 and 1000℃, which are controlled by the growth of the inner Cr-rich layer, and that after oxidation at 1050℃ for 200 h, it almost exhibits the linear oxidation kinetics possible due to the volatility of Cr-rich oxide. A mixed scale forms on the alloy after prolonged oxidation. The oxide scale formed at 900 and 1000℃ is composed of an outer layer of spinel and an inner continuous Cr-rich layer and at 1050℃ is composed of a very discontinuous Cr-rich layer.
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Co-base superalloy
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WANG Shuhe
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DAI Tongfu
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SHI Changxu
材料科学技术（英）
The effect of La element on the mechanical properties and constitution nearby grain boundary in a Co-base superalloy Co-22Ni-22Cr-14k during 760℃ ageing has been investigated by AES and material testing. Results show that element La can be in a state of solid solution and segregates mainly at the vicinity of grain boundaries. The prior segregation of La atoms can affect segregation behaviour of other elements, so that exerts influence on microstructure of the alloy, Particularly increasing of La content can decrease P concentration at the vicinity of grain boundaries but not decrease S concentration. S together with La produce cosegregation effect. The content of La has no obvious effect on high temperature strength. When the content of La comes up to 0.02wt-%, it can obviously improve the high temperature ductility.
关键词:
La
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