热处理条件下激光原位合成高铌Ti-Al金属间化合物复合涂层的微结构特征
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摘要
为了提高钛合金的高温抗氧化性能,推动钛合金在高温和复杂工况环境下的进一步工程应用,利用高能激光束作用下Ti、Al、Nb三种元素混合粉末之间的原位反应在BT3-1钛合金表面制备了高温抗氧化的高铌Ti-Al金属间化合物复合涂层。针对原位反应所制备涂层存在的缺陷,通过自行设计的热处理工艺优化了涂层和界面微观组织。借助光学显微镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)分析了热处理前后复合涂层的物相结构及显微形貌。结果表明:热处理前的涂层主要由单质Nb、金属间化合物γ-TiAl、α_2-Ti_3Al、Ti_3Al_2等物相组成;热处理后的复合涂层,单质Nb固溶到γ-TiAl和α_2-Ti_3Al中,同时形成了新相Ti_3AlNb_(0.3),涂层近似为γ-TiAl+α_2-Ti_3Al双相层片状等轴晶组织。此外,涂层中并未观察到减弱抗氧化性的单质Nb颗粒和Ti_3Al_2相,Ti、Al、Nb的宏观偏析得以消除,涂层与基材界面位置的气孔和裂纹均以消失,出现了明显的白亮带冶金结合过渡层,涂层组织也更加均匀致密。热处理对提高钛合金表面Nb的合金化程度和改善Ti-Al金属间化合物的高温抗氧化性能起到了显著的促进作用。
In order to improve the high-temperature oxidation resistance and further promote the engineering application of titanium alloy in high temperature and complex service environment conditions,high niobium Ti-Al intermetallic compound oxidation resistance coatings were prepared on BT3-1titanium alloy surface by laser in situ synthesis process.Microstructure of the composite coating and interface was optimized through a self-designed heat treatment process according to the defects in the coating.The phase structure and microstructure of the coating before and after heat treatment were analyzed by Optical Microscope(OM),X-Ray Diffraction(XRD)and Scanning Electron Microscopy(SEM).The results show that the coating mainly consists of Nb,intermetallicγ-TiAl,α_2-Ti_3Al and Ti_3Al_2 phases before heat treatment.But after heat treatment,the Nb is dissolved inγ-TiAl and α_2-Ti_3Al,and new phase Ti_3AlNb_(0.3) is observed in the coating.The microstructure of the coating is approximatelyγ-TiAl+α_2-Ti_3Al biphasic lamellar equiaxed grains structure.Moreover,the element Nb particle and Ti_3Al_2 phase which weaken inoxidizability are not observed in the coating.The macro segregation of Ti,Al and Nb is eliminated,and the pores or cracks at interface positions between the composite coating and substrate are disappeared.A distinct white band transition metallurgical bonding layer is generated,and the microstructure of the coating is more uniform and dense.Heat treatment plays an important role in improving the Nb alloying extent on titanium alloy surface and increasing the high temperature oxidation resistance of the Ti-Al intermetallic composite coating.
In order to improve the high-temperature oxidation resistance and further promote the engineering application of titanium alloy in high temperature and complex service environment conditions,high niobium Ti-Al intermetallic compound oxidation resistance coatings were prepared on BT3-1titanium alloy surface by laser in situ synthesis process.Microstructure of the composite coating and interface was optimized through a self-designed heat treatment process according to the defects in the coating.The phase structure and microstructure of the coating before and after heat treatment were analyzed by Optical Microscope(OM),X-Ray Diffraction(XRD)and Scanning Electron Microscopy(SEM).The results show that the coating mainly consists of Nb,intermetallicγ-TiAl,α_2-Ti_3Al and Ti_3Al_2 phases before heat treatment.But after heat treatment,the Nb is dissolved inγ-TiAl and α_2-Ti_3Al,and new phase Ti_3AlNb_(0.3) is observed in the coating.The microstructure of the coating is approximatelyγ-TiAl+α_2-Ti_3Al biphasic lamellar equiaxed grains structure.Moreover,the element Nb particle and Ti_3Al_2 phase which weaken inoxidizability are not observed in the coating.The macro segregation of Ti,Al and Nb is eliminated,and the pores or cracks at interface positions between the composite coating and substrate are disappeared.A distinct white band transition metallurgical bonding layer is generated,and the microstructure of the coating is more uniform and dense.Heat treatment plays an important role in improving the Nb alloying extent on titanium alloy surface and increasing the high temperature oxidation resistance of the Ti-Al intermetallic composite coating.
引文
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[2]WENG F,CHEN C Z,YU H J.Research status of laser cladding on titanium and its alloys:A review[J].Materials&Design,2014,58:412-425.
[3]CASTILLO-RODRI GUEZ M,NO M L,JIMENEZ J A,et al..High temperature internal friction in a Ti-46Al-1Mo-0.2Si intermetallic,comparison with creep behaviour[J].Acta Materialia,2016,103:46-56.
[4]赵志伟,王续跃,于冬洋,等.中间层法钛/钢层合板激光熔覆制备及性能[J].光学精密工程,2016,24(10):12-19.ZHAO ZH W,WANG X Y,YU D Y,et al..Preparation and properties of titanium clad steel plate with interlayer in laser cladding[J].Opt.Precision Eng.,2016,24(10):12-19.(in Chinese)
[5]史吉鹏,周彦彬,刘黎明.钛合金厚板激光-电弧复合热源打底焊工艺[J].光学精密工程,2016,24(10):280-286.SHI J P,ZHOU Y B,LIU L M.Root welding process in laser-TIG hybrid welding of titanium alloy thick plate[J].Opt.Precision Eng.,2016,24(10):280-286.(in Chinese)
[6]SHI Z W,WEI H,ZHANG H Y,et al..Investigation of a hot-pressed Nb-Ti-Al alloy:Mechanical alloying,microstructure and mechanical property[J].Materials Science and Engineering:A,2016,651:869-877.
[7]刘洪喜,陶喜德,张晓伟,等.机械振动辅助激光熔覆Fe-Cr-Si-B-C涂层的显微组织及界面分布形态[J].光学精密工程,2015,23(8):2192-2202.LIU H X,TAO X D,ZHANG X W,et al..Microstructure and interface distribution of Fe-Cr-Si-BC laser cladding alloy coatings assisted by mechanical vibration[J].Opt.Precision Eng.,2015,23(8):2192-2202.(in Chinese)
[8]CHEN L,YANG Y,WU M J,et al..Correlation between arc evaporation of Ti-Al-N coatings and corresponding Ti0.50 Al0.50 target types[J].Surface and Coatings Technology,2015,275:309-315.
[9]LIU H X,ZHANG X W,JIANG Y H,et al..Microstructure and high temperature oxidation resistance of in-situ synthesized TiN/Ti3Al intermetallic composite coatings on Ti6Al4V alloy by laser cladding process[J].Journal of Alloys and Compounds,2016,670:268-274.
[10]TEPPERNEGG T,ANGERER P,KLUNSNER T,et al..Evolution of residual stress in Ti-AlTa-N coatings on hard metal milling inserts[J].International Journal of Refractory Metals and Hard Materials,2015,52:171-175.
[11]ABI-TANNOUS T,SOUEIDAN M,FERRO G,et al..Parametric investigation of the formation of epitaxial Ti3SiC2on 4H-SiC from Al-Ti annealing[J].Applied Surface Science,2015,347:186-192.
[12]SHI Z W,WEI H,ZHANG H Y,et al..Nanotwinned Ti(O,C)induced by oriented attachment in a hot-pressed Nb-Ti-Al alloy[J].Acta Materialia,2016,105:114-120.
[13]ZHANG D Q,WU J Y,LI B,et al..Preparation of ceramic membranes on porous Ti-Al alloy supports by an in-situ oxidation method[J].Journal of Membrane Science,2015,476:554-560.
[14]ZHANG Q,CHEN J,WANG L L,et al..Solidification microstructure of laser additive manufactured Ti-6Al-2Zr-2Sn-3Mo-1.5Cr-2Nb titanium alloy[J].Journal of Materials Science&Technology,2016,32(4):381-386.
[15]LI D K,CHEN J F,ZOU C W,et al..Effects of Al concentrations on the microstructure and mechanical properties of Ti-Al-N films deposited by RF-ICPIS enhanced magnetron sputtering[J].Journal of Alloys and Compounds,2014,609:239-243.
[16]FAROOQ M U,KHALID F A,ZAIGHAM H,et al..Superelastic behaviour of Ti-Nb-Al ternary shape memory alloys for biomedical applications[J].Materials Letters,2014,121:58-61.
[17]陈国良.金属间化合物结构材料研究现状与发展[J].材料导报,2000,14(9):1-5.CHEN G L.R&D status and prospect on the ordered structural intermetallics[J].Materials Review,2000,14(9):1-5.(in Chinese)
[18]郑传林,徐重,贺志勇,等.TiAl金属间化合物高温抗氧化研究进展[J].材料导报,2002,16(11):14-16.ZHENG CH L,XU ZH,HE ZH Y,et al..Progress in research on high temperature oxidation resistance of TiAl intermetallics[J].Materials Review,2002,16(11):14-16.(in Chinese)
[19]丁晓非.Ti-Al-Nb三元系中的合金组织对性能的影响[D].大连:大连理工大学,2014.DING X F.Effect of Microstructures on Mechanical Properties for Ti-Al-Nb Ternary Alloys[D].Dalian:Dalian University of Technology,2014.(in Chinese)
[20]DIMIDUK D M.Gamma titanium aluminide alloys—an assessment within the competition of aerospace structural materials[J].Materials Science and Engineering:A,1999,263(2):281-288.
[21]JIANG H R,HIROHASI M,LU Y,et al..Effect of Nb on the high temperature oxidation of Ti-(0-50at.%)Al[J].Scripta Materialia,2002,46(9):639-643.
[22]KOO C H,YU T H.Pack cementation coatings on Ti3Al-Nb alloys to modify the high-temperature oxidation properties[J].Surface and Coatings Technology,2000,126(2-3):171-180.
[23]KENEL C,LEINENBACH C.Influence of Nb and Mo on microstructure formation of rapidly solidified ternary Ti-Al-(Nb,Mo)alloys[J].Intermetallics,2016,69:82-89.
[24]BAI R,ZHENG X,LI Z K,et al..Precipitation strengthening mechanism of Nb-Ti-Al alloys[J].Procedia Engineering,2012,27:1241-1247.
[25]马丁.基于Thermo-Calc的Ti-Al-X三元合金相图热力学计算[D].哈尔滨:哈尔滨工业大学,2007.MA D.Thermodynamic Calculation of Ti-Al-X Phase Diagrams Based on Thermo-Calc Software[D].Harbin:Harbin Institute of Technology,2007.(in Chinese)