TiAl及TiAl-9Nb合金抗热腐蚀性能研究
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摘要
研究了TiAl及TiAl-9Nb合金在850℃下25%NaCl+75%Na_2SO_4(质量分数)熔盐中的热腐蚀行为,采用扫描电子显微镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)分析了腐蚀产物膜的结构和相组成。结果表明:TiAl和TiAl-9Nb合金的腐蚀产物均主要由TiO_2, Al_2O_3和少量的TiS组成,腐蚀产物膜结构疏松,容易剥落,对基体的保护性很差。在热腐蚀过程中, NaCl对TiAl和TiAl-9Nb合金的表面氧化膜造成了破坏,生成的Cl_2导致了表面氧化膜的开裂;继而O和S对TiAl合金中的α_2相、 TiAl-9Nb合金中的β相产生了内氧化、内硫化的选择性腐蚀。与普通TiAl合金相比, TiAl-9Nb合金具有更优异的抗热腐蚀性能,这归因于TiAl-9Nb合金中β相较高的Al含量以及β相与α_2相之间组织结构的差异。
Hot corrosion behavior of TiAl and TiAl-9 Nb alloys in molten salt environment of 25%NaCl+75%Na_2SO_4(mass fraction) at 850 ℃ was investigated. Scanning electron microscope(SEM), energy dispersive X-ray spectrometer(EDS) and X-ray diffractometer(XRD) were employed to investigate the surface morphologies, microstructures and phase constitutions of the corrosion films. The results show that the corrosion products of both TiAl and TiAl-9 Nb alloys were mainly composed of TiO_2, Al_2O_3 and a small amount of TiS. The corrosion film was loose and easy to peel off, and thus had little protective effects to the substrate. During hot corrosion, NaCl broke the protective scales formed on TiAl and TiAl-9 Nb alloys by producing corrosive Cl_2, and then, selective corrosion characterized by internal oxidation and internal sulfide occurred along the α_2 phase in TiAl and β phase in TiAl-9 Nb. The higher concentration of Al in β phase in TiAl-9 Nb alloy than that of α_2 phase in TiAl alloy, as well as the structural differences between the two phases should be the main reasons responsible for the better hot corrosion resistance of TiAl-9 Nb than TiAl.
Hot corrosion behavior of TiAl and TiAl-9 Nb alloys in molten salt environment of 25%NaCl+75%Na_2SO_4(mass fraction) at 850 ℃ was investigated. Scanning electron microscope(SEM), energy dispersive X-ray spectrometer(EDS) and X-ray diffractometer(XRD) were employed to investigate the surface morphologies, microstructures and phase constitutions of the corrosion films. The results show that the corrosion products of both TiAl and TiAl-9 Nb alloys were mainly composed of TiO_2, Al_2O_3 and a small amount of TiS. The corrosion film was loose and easy to peel off, and thus had little protective effects to the substrate. During hot corrosion, NaCl broke the protective scales formed on TiAl and TiAl-9 Nb alloys by producing corrosive Cl_2, and then, selective corrosion characterized by internal oxidation and internal sulfide occurred along the α_2 phase in TiAl and β phase in TiAl-9 Nb. The higher concentration of Al in β phase in TiAl-9 Nb alloy than that of α_2 phase in TiAl alloy, as well as the structural differences between the two phases should be the main reasons responsible for the better hot corrosion resistance of TiAl-9 Nb than TiAl.
引文
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[3] Cheng Y Y,Zhang S Z,Kong F T,Liu Z Y,Lin J P.Progress in β-solidifying γ-TiAl based alloys [J].Chinese Journal of Rare Metals,2012,36(1):154.(陈玉勇,张树志,孔凡涛,刘祖岩,林均品.新型β-γ TiAl合金的研究进展 [J].稀有金属,2012,36(1):154.)
[4] Zhang Y,Wang X P,Kong F T,Chen Y Y.Effects of alloying additions on hot deformation processing of TiAl alloys [J].Rare Metal Materials and Engineering,2017,46(11):3571.(张宇,王晓鹏,孔凡涛,陈玉勇.合金成分对TiAl合金热变形加工影响的研究进展 [J].稀有金属材料与工程,2017,46(11):3571.)
[5] Liu N,Li Z,Xu W Y,Wang Y,Zhang G Q.Hot deformation behavior and micro-structural evolution of power metallurgical TiAl alloy [J].Rare Metals,2017,36(4):236.
[6] Clemens H,Chladil H F,Qallgram W,Zickler G A,Gerling R,Liss K D,Kremmer S,Guther V,Smarsly W.In and exsitu investigations of the β-phase in a Nb and Mo containing γ-TiAl based alloy [J].Intermetallics,2008,16(6):827.
[7] Cheng Y Y,Yang F,Kong F T,Xiao S L.Processing,microstructure and properties of Ti-43Al-9V-0.3Y alloy [J].Materials China,2010,29(3):12.(陈玉勇,杨非,孔凡涛,肖树龙.TiAl合金的热加工、 组织和性能 [J].中国材料进展,2010,29(3):12.)
[8] Mitoraj M,Godlewska E,Heintz O,Geoffroy N,Fontana S,Chevalier S.Scale composition and oxidation mechanism of the Ti-48Al-8Nb alloy in air at 700 and 800 ℃ [J].Intermetallics,2011,(19):39.
[9] Lin J P,Zhang L Q,Song X P,Ye F,Chen G L.Status of research and development of light-weight γ-TiAl intermetalic based compounds [J].Materials China,2010,29(2):1.(林均品,张来启,宋西平,叶丰,陈国良.轻质γ-TiAl金属间化合物的研究进展 [J].中国材料进展,2010,29(2):1.)
[10] Lin J P,Zhao L L,Li G Y,Zhang L Q,Song X P,Ye F,Chen G L.Effect of Nb on oxidation behavior of high Nb containing TiAl alloys [J].Intermetallics,2011,19(2):131.
[11] Liu J,Xue X Y,Liu J R.Oxidation behavior and oxide scale characteristics of TiAl-Nb alloy with full lamellar microstructure at high temperature [J].Rare Metal Materials and Engineering,2015,44(7):1942.(刘杰,薛祥义,杨劼人.全片层组织TiAl-Nb合金的高温氧化行为及氧化层结构表征 [J].稀有金属材料与工程,2015,44(7):1942.)
[12] Sun Y R,Li H Q,Zhang W W,Yu X F.Effect of V on hot corrosion beha vior of K417G alloy at 900 ℃ [J].Rare Metal Materials and Engineering,2017,46(9):2571.(孙雅茹,李海全,张薇薇,于兴福.V对K417G合金高温热腐蚀行为的影响 [J].稀有金属材料与工程,2017,46(9):2571.)
[13] Ma J,Jiang S M,Gong J,Sun C.Hot corrosion properties of composite coatings in the presence of NaCl at 700 and 900 ℃ [J].Corrosion Science,2013,70:29.
[14] Godlewska E,Mitoraj M,Leszczynska K.Hot corrosion of Ti-46Al-8Ta (at.%) intermetallic alloy [J].Corrosion Science,2014,78:63.
[15] Jin G X,Li J X,Qi H B,Qiao L J,Gao K W,Qiao B J,Chu W Y.Investigation of hot corrosion of (Al,Mn)3Ti-2V intermetallics [J].Acta metallurgica Sinica,2004,40(2):185.(金光熙,李金许,齐慧滨,乔利杰,高克玮,桥本健纪,褚武扬.(Al,Mn)3Ti-2V金属间化合物的热腐蚀研究 [J].金属学报,2004,40(2):185.)
[16] Zhao W Y,Xu B W,Ma Y,Gong S K.Inter-phase selective corrosion of γ -TiAl alloy in molten salt environment at high temperature [J].Materials International,2011,21:322.
[17] Jin G X,Qiao L J,Gao K W,T Kimura,K Hashimoto,Chu W Y.Effect of microstructure on hot corrosion behavior of TiAl intermetallics [J].Chinese Journal of Nonferrous Metals,2004,14(2):210.(金光熙,乔利杰,高克玮,Kimura T,Hashimoto K,褚武扬.显微组织对TiAl 合金热腐蚀行为的影响 [J].中国有色金属学报,2004,14(2):210.)