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isothermal oxidation behavior of scandium and yttrium co-doped B2-type iron-aluminum intermetallics at elevated temperature

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Rare Metals 2018年第8期37卷 690-698页

作者： Dong-Qing Li Li-Xian Zhou Kuan-Jun Zhu Jian Gu Shu-Hui Zheng Department of Transmission and Transformation Engineering Mechanics China Electric Power Research Institute

B2 FeA1 intermetallic compounds modified with reactive elements （REs） including Sc and Y were fabricated by vacuum arc-melting, and the isothermal oxidation behavior of the RE-doped alloys at 1373 K was investigated. Both Sc and Y single-doping significantly decrease the alumina film growth rate of the alloys. The alumina film growth rate of Sc＋ Y co-doped alloy even further reduces compared to that of the Sc and Y single-doped alloys. The synergistic effect produced by Sc＋ Y codoping on the growth behavior of alumina was discussed. It could be anticipated that the combined additions of Sc and Y which have matched chemical properties might decrease the alumina film growth rate more effectively and provide FeA1 alloys with enhanced oxidation resistance.

关键词： Ferritic aluminides Reactive elements Codoping isothermal oxidation Segregation

isothermal oxidation behavior of a new Re-free nickel-based single-crystal superalloy at 950℃

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Rare Metals 2017年第8期36卷 617-621页

作者： Xue-Feng Zhou Guang Chen Ya-Ya Feng Zhi-Xiang Qi Min-Zhi Wang Pei Li Jia-Lin Cheng Engineering Research Center of Materials Behavior and Design Ministry of Education Nanjing University of Science and TechnologyNanjing 210094China School of Chemistry and Materials Engineering Changshu Institute of TechnologyChangshu 215500China School of Materials Science and Engineering Nanjing Instituteof TechnologyNanjing 211167China

The isothermal oxidation behavior of a new Refree nickel-based single-crystal superalloy in air at 950 ℃ for 200 h was studied by scanning electron microscopy（SEM）with energy-dispersive spectroscopy（EDS）and X-ray diffraction（XRD）.The results indicate that oxidation kinetics obeys parabolic law approximately,and the mass gain increases rapidly during initial oxidation stage and then gradually slows *** oxidation scales are composed of three layers：the outer layer mainly consists of NiO with a small amount of CoO;the intermediate layer is mainly composed of Cr_2O_3 with a small amount of spinel compounds such as CrTaO_4,NiCr_2O_4,CoCrAl_2O_4,CoAl_2O_4,and NiAl_2O_4;and the inner layer is composed of Al_2O_*** Al_2O_3 layer suppresses the diffusion of elements between oxygen and alloy elements,slows down the alloy oxidation speed,and also suppresses the growth of the oxide scale and reduces the oxidation rate,which is agreeable with the oxidation kinetics.

关键词： Nickel-based single-crystal superalloy isothermal oxidation oxidation kinetic Surfacemorphology

isothermal oxidation Behavior of Dysprosium/S-Doped β-NiAl Alloys at 1200°C

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Journal of Materials Science & Technology 2014年第3期30卷 229-233页

作者： Lu Wang Dongqing Li Jian Chang Hongbo Guo Shengkai Gong Huibin Xu School of Materials Science and Engineering Beihang University AVIC Shenyang Liming Aero-engine Group Corporation Ltd.

A β--NiAI alloy with normal purity, a S-doped and a Dy and S co-doped （Y-NiAI alloys were prepared by arc-melting and their corresponding S contents were less than 20 ×10-6, 33 ×10-6 and 22 × 10-6, respectively. The isothermal oxidation behavior of the alloys at 1200 ℃ was investigated and the extent of S segregation at the scale-alloy interface was determined by scanning Auger microscopy. S-doping had no significant effect on the phase transformation rate from e- to β-Al2O3, while the addition of Dy retarded this process. For the S- doped alloy, scale rumpling occurred only after 2 h thermal exposure and numerous large voids were observed at the scale-alloy interface where S segregated. In contrast to this, the oxide scale formed on the Dy and S co-doped alloy still remained flat even after 50 h isothermal oxidation and only small voids existed at the interface where S segregation was not detected.

关键词： NiAl Dy S isothermal oxidation Phase transformation Segregation

Microstructure and isothermal oxidation of 3Al_2O_3·2SiO_2/SiC coating on high and low density carbon-carbon composites

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Journal of Central South University 2013年第1期20卷 30-36页

作者： L.GBOLOGAH 熊翔郝安林曾毅张武装 State Key Laboratory for Powder Metallurgy Central South University Anyang Institute of Technology

Carbon-carbon composite （C/C） materials are prone to severe oxidation and volatilization problems. To address these issues, mullite （3Al2O3.2SiO2）/silicon carbide （SIC） coatings were deposited on C/C composite substrates characterized into high and low densities. The coatings were applied by a two-step approach： pack cementation and silica sol based slurry coating processes. The relationship between the microstructure of 3Al2O3·2SiO2/SiC coatings and C/C substrates during isothermal oxidation cycle at 1 500 ℃ was investigated using X-ray diffractometer （XRD） and scanning electron microscope （SEM） mounted with energy dispersive spectrometer （EDS）. The results indicate that the density of the substrates has a marked effect on the coatings. Dense, thick and well-bonded coatings are obtained in the high density substrate. After 106 h of isothermal oxidation, the high density substrate with 3Al2O3-2SiO2/SiC coating offers effective protection as compared to low density substrate suffering recession.

关键词： mullite carbon-carbon composite slurry coating isothermal oxidation

Effects of surface modification on isothermal oxidation behavior of HVOF-sprayed NiCrA1Y coatings

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Progress in Natural Science:Materials International 2011年第2期21卷 173-179页

作者： Li-yong NI,Zi-long WU,Chun-gen ZHOU Key Laboratory of Aerospace Materials and Performance(Ministry of Education), Department of Materials Science and Engineering,Beihang University,Beijing 100191,China Key Laboratory of Aerospace Materials and Performance (Ministry of Education) Department of Materials Science and Engineering Beihang University Beijing 100191 China

NiCrAlY coatings were deposited on Ni-based superalloy by high-velocity oxygen-fuel spraying(HVOF).Surface modification by means of grit-blasted,shot-peened and ground methods was used in order to study the effect of surface conditions on the isothermal oxidation behavior of HVOF-sprayed NiCrAlY coatings at 1 050℃.The results showed that surface modification had an obvious effect on the isothermal oxidation behavior of the *** was a large decrease in growth rate compared with the as-sprayed *** scale formed on the grit-blasted and shot-peened coatings was a mixture of Al2O3and NiCr2O4,while the oxide formed on the ground coating was composed mainly of *** surface modification,the content of NiCr2O4spinels decreased compared with the as-sprayed coating.

关键词： NiCrAlY HVOF isothermal oxidation thermal barrier coating

isothermal oxidation behavior of TiAl intermetallics with different oxygen contents

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Transactions of Nonferrous Metals Society of China 2019年第3期29卷 526-533页

作者： Kun ZHAO Si-hui OUYANG Yong LIU Bin LIU Xiao-peng LIANG Hui-zhong LI Yu WANG State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China School of Materials Science and Engineering Central South University Changsha 410083 China Department of Modern Mechanics University of Science & Technology of China Hefei 230027 China

isothermal oxidation behaviors of Ti-45Al-2Fe-2Mo-1Cr intermetallics with different oxygen contents were studied under the condition of 950 °C, 100 h in air, and the oxidation kinetic parameters were also evaluated. The results show that the oxidation resistance of the TiAl intermetallics is negatively related to the oxygen content, and both the mass gain and thickness of oxide scale increase with the oxygen content. The sub-surface microstructure of the oxide scales varies with the oxygen content. Z phase is observed in the sub-surface area of the low-oxygen-content alloy, while the τ2(Al2FeTi) phase is found in the medium-oxygen-content and the high-oxygen-content alloys. The deterioration of oxidation resistance is due to the enhanced internal oxidation with the increase of oxygen content. It is possible to improve the oxidation resistance by controlling the oxygen content.

关键词： TiAl intermetallics oxygen content isothermal oxidation oxidation kinetic

Comparison of isothermal oxidation Behavior of Co-10Cr-xSi(x=0,5,10)Alloys at 1 073K

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Journal of Beijing Institute of Technology 2018年第3期27卷 379-384页

作者： Junhuai Xiang Ling Wang Honghua Zhang Lingyun Bai Changjun Wan Ganlan Yang Jiangxi Key Laboratory of Surface Engineering Jiangxi Science and Technology Normal University

The oxidation behavior of Co-10 Cr-xSi(x=0,5,10,nominal composition,at%)alloys in 0.1 MPa pure O2 at 1 073 Kwas ***-10 Cr presents the worst oxidation resistance with the mass gain of about 7.531 mg/cm2 after 24 hoxidation,while Co-10 Cr-10 Si presents the best oxidation resistance with the much lower mass gain of about 0.078 mg/***-10 Cr-10 Si is about two magnitudes lower than that of Co-10 *** oxidation behavior of Co-10 Cr-5 Si is intermediate between that of Co-10 Cr and Co-10 Cr-10 *** nodular oxides have occupied most of the alloy surface,and their microstructure is similar to Co-10 Cr,to some *** the contrary,only a fraction of the surface is covered by the Cr2 O3 layer,whose microstructure is similar to that of Co-10 Cr-10 Si.

关键词： cobalt-chromium-silicon isothermal oxidation high temperature microstructure

Effects of supersonic fine particles bombarding on thermal barrier coatings after isothermal oxidation

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Transactions of Nonferrous Metals Society of China 2012年第7期22卷 1629-1637页

作者：韩玉君叶福兴丁坤英王志平陆冠雄天津大学材料科学与工程学院天津市现代连接技术重点实验室天津300072 天津大学内燃机燃烧学国家重点实验室天津300072 中国民航大学理学院天津300300

This work was attempted to modify the current technology for thermal barrier coatings（TBCs） by adding an additional step of surface modification,namely,supersonic fine particles bombarding（SFPB） process,on bond coat before applying the *** isothermal oxidation at 1000 °C for different time,the surface state of the bond coat and its phase transformation were investigated using X-ray diffraction（XRD）,scanning electron microscopy（SEM） equipped with energy-dispersive X-ray spectrometry（EDS）,transmission electron microscopy（TEM） and Cr3＋ luminescence *** dislocation density significantly increases after SFPB process,which can generate a large number of diffusion channels in the area of the surface of the bond *** the initial stage of isothermal oxidation,the diffusion velocity of Al in the bond coat significantly increases,leading to the formation of a layer of stable α-Al2O3 phase.A great number of Cr3＋ positive ions can diffuse via diffusion channels during the transient state of isothermal oxidation,which can lead to the presence of（Al0.9Cr0.1）2O3 phase and accelerate the γ→θ→α phase ***3＋ luminescence spectroscopy measurement shows that the residual stress increases at the initial stage of isothermal oxidation and then *** residual stress after isothermal oxidation for 310 h reduces to 0.63 GPa compared with 0.93 GPa after isothermal oxidation for 26 *** order to prolong the lifespan of TBCs,a layer of continuous,dense and pure α-Al2O3 with high oxidation resistance at the interface between topcoat and bond coat can be obtained due to additional SFPB process.

关键词： thermal barrier coatings(TBCs) supersonic fine particles bombarding(SFPB) isothermal oxidation Cr3+ luminescence spectroscopy dislocation density diffusion channel

oxidation behaviors of Co-Al-W-0.1B superalloys in a long-term isothermal exposure at 900~?C

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Journal of Materials Science & Technology 2018年第11期34卷 2212-2217页

作者： Yuzhi Li Florian Pyczak Jonathan Paul Zekun Yao School of Materials Science and Engineering Northwestern Polytechnical UniversityXi'an 710072China Institute of Materials Research Helmholtz-Zentrum Geesthacht21502 GeesthachtGermany

Co-Al-W-0.1B superalloys have been isothermally oxidized at 900℃ for 1000,5000 and 10000 h in order to investigate their oxidation *** oxide layers and morphologies were characterized by X-ray diffraction and scanning electron microscopy combined with energy-dispersive ***1000 h exposure,a Co3W/γ zone,an Al2O3layer,a mixture of Co,Al,W oxides layer and a CoO layer are established on the substrate *** extended oxidation,a discontinuous Al2O3layer in Co-9Al-8W-0.1B and Co-9Al-9W-0.1B alloys leads to an additional mixed oxide layer on the substrate instead of the Co3W/γ *** oxide layers that form on the Co-9Al-8W-0.1B and Co-9Al-9W-0.1B alloys are much thicker than those on the Co-9Al-11W-0.1B alloy,and continuously thicken during *** higher content of W is beneficial to improving the oxidation resistance as it facilitates a faster formation of Co3Was well as Al2O3.

关键词： isothermal oxidation CoO layer Al2O3 layer Co3W/γ