钛铝低压涡轮叶片熔模铸造精确成形及冶金缺陷分析
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摘要
目的研究不同浇冒口设置对Ti Al低压涡轮叶片的成形的影响及叶片冶金缺陷形成的原因。方法采用熔模精铸方法,通过设计顶注式重力铸造浇注系统,采用冷坩埚感应熔炼炉进行Ti Al叶片浇注实验,采用目视和X射线检验方法分析叶片铸件表面及内部缺陷,并结合金属凝固理论分析缺陷形成原因。结果合理的浇口和排气孔设置有效避免了因熔体流动性差造成的叶片充型不完整,以及凝固收缩导致的应力开裂等问题,浇注出成形完整的铸造叶片;叶冠与叶身端部转角部位充型凝固过程中形成热节,容易出现贯穿性疏松缺陷;树脂基熔模焙烧后残留的碳黑在熔体充型凝固过程中,与面层中的Zr O2反应生产CO,导致叶身出现聚集性皮下气孔;由于凝固收缩引起叶身与铸型分离,降低横向散热能力,导致叶盆部位出现表面疏松。结论通过浇注合理的浇注系统设置可实现Ti Al叶片完整充型,疏松缺陷控制为进一步提高叶片质量的关键。
The paper aims to study influences of different sprue and risers setting on forming of Ti Al low pressure turbine blades and the reasons for its metallurgical defects.The investment casting method was adopted and top gating system of gravity casting was designed to carry out Ti Al blade casting experiment with cold crucible induction melting furnace.Internal and external metallurgical defects were respectively inspected by visual inspection and X-ray inspection technology,and the cause of defect formation was deduced by metal solidification theory analysis.It was evitable to prevent misrun cause of low melt fluidity and cracking cause of shrinkage stress by setting up reasonable gate and vent,and acquire complete blade casting.Hot spot prone to form in the corner of the shroud and blade body during filling and solidification process,which lead to penetrating porous defects.Carbon black brought by sintering of residual resin reacted with Zr O2 in investment precoat,resulting in aggregated distribution of subsurface blowhole.Separation of the blade body and the mould caused by solidification shrinkage reduced the ability of transverse cooling,leading to formation of surface porosity.Complete filling of Ti Al blades can be achieved by reasonable setting of pouring system.While the control of porous defects is the key to further improve the quality of the blades.
The paper aims to study influences of different sprue and risers setting on forming of Ti Al low pressure turbine blades and the reasons for its metallurgical defects.The investment casting method was adopted and top gating system of gravity casting was designed to carry out Ti Al blade casting experiment with cold crucible induction melting furnace.Internal and external metallurgical defects were respectively inspected by visual inspection and X-ray inspection technology,and the cause of defect formation was deduced by metal solidification theory analysis.It was evitable to prevent misrun cause of low melt fluidity and cracking cause of shrinkage stress by setting up reasonable gate and vent,and acquire complete blade casting.Hot spot prone to form in the corner of the shroud and blade body during filling and solidification process,which lead to penetrating porous defects.Carbon black brought by sintering of residual resin reacted with Zr O2 in investment precoat,resulting in aggregated distribution of subsurface blowhole.Separation of the blade body and the mould caused by solidification shrinkage reduced the ability of transverse cooling,leading to formation of surface porosity.Complete filling of Ti Al blades can be achieved by reasonable setting of pouring system.While the control of porous defects is the key to further improve the quality of the blades.
引文
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[2]KIM Y W,KIM S L.Advances in Gamma alloy Materials-Processes-Application Technology:Successes,Dilemmas,and Future[J].JOM,2018,70(4):533—541.
[3]RUI Y.Advances and Challenges of Ti Al Base Alloys[J].Acta Metallurgica Sinica,2015,51(2):129—147.
[4]KUNAL K R,NORMANM,WERELEY.Advances in Gamma Titanium Aluminides and Their Manufacturing Techniques[J].Progress in Aerospace Sciences,2012,55:1—16.
[5]CLEMENS H,MAYER S.Intermetallic Titanium Aluminides in Aerospace Applications-Processing,Microstructure and Properties[J].High Temperature Technology,2016,33(4/5):560—570.
[6]AGUILAR J,SCHIEVENBUSCH A,K?TTLITZ O.Investment Casting Technology for Production of Ti Al Low Pressure Turbine Blades-Process Engineering and Parameter Analysis[J].Intermetallics,2011,19(6):757—7613.
[7]JARVIS D J,VOSS D.Impress Integrated Project-an Overview Paper[J].Materials Science&Engineering A,2005,413(6):583—591.
[8]LASALMONIE A.Intermetallics:Why is it so Difficult to Introduce them in Gas Turbine Engines[J].Intermetallics,2006,14:1123—1130.
[9]GEBAUER K.Performance,Tolerance and Cost of Ti Al Passenger Car Valves[J].Intermetallics,2006,14(4):355—360.
[10]YANG L,YAO Q,ZHANG L,et al.Numerical Simulation of High Nb-Ti Al Low Pressure Turbine Blades Centrifugal Casting Based on Procast[J].Foundry Technology,2014,35(12):2945—2947.
[11]KUANG J P,HARDING R A,CAMPBELL J.Examination of Defects in Gamma Titanium Aluminide Investment Castings[J].Cast Metals,2000,13(3):125—134.
[12]ESKIN D G,KATGERMAN L.A Quest for a New Hot Tearing Criterion[J].Metallurgical&Materials Transactions A,2007,38(7):1511—1519.
[13]CUI Y,TANG X,GAO M,et al.Interaction Between Ti Al Alloy and Diacetatozirconic Acid-bonded Yttria Mould Under High-temperature and Long-term[J].Rare Metal Materials&Engineering,2012,41(7):1171—1175.
[14]MAITRE A,LEFORT,PIERRE.Solid State Reaction of Zirconia with Carbon[J].Solid State Ionics,1997,104(1):109—120.
[15]HARDING R A,WICKINS M,WANG H,et al.Development of a Turbulence-free Casting Technique for Titanium Aluminides[J].Intermetallics,2011,19(6):805—814.
[16]WANG H,DJAMBAZOV G,PERICLEOUS K.Analysis of Heat Transfer Through the Casting-mould Interface Including Gas-gap Effect and Application to Ti Al Castings[J].International Journal of Numerical Methods for Heat&Fluid Flow,2013,23(4):707—724.