Preparation of complex thin-walled TiAl alloy swirlers by powder injection molding
As an important component of aeroengines,the lightweight manufacturing of swirlers is of great significance for improving the service performance of engines.Lightweight,high-strength,and heat-resistant TiAl alloy is a high-temperature structural material with great application potential,but its inherent brittleness and difficulty in preparation and processing seriously limit its application in the fabrication of high-performance swirlers.Therefore,the powder injection molding(PIM)technology was used to prepare the complex thin-walled TiAl alloy swirlers in near-net shape without any machining process by combining the mold design method of water-soluble core and high conformal polyformaldehyde(POM)-based binders.The preparation processes mainly include catalytic debinding,thermal debinding,and two-step sintering.The results show that the binder with a composition of 82%(mass fraction,the same below)POM-5%high density polyethylene(HDPE)-5%ethylene-vinyl acetate copolymer(EVA)-8%stearic acid(SA)has a higher powder loading and better molding filling performance.The powder loading,the flow behavior index n,the viscous flow activation energy E,and the general rheological index αSTV of the feedstock are 62%(volume fraction),0.56,22.95 kJ/mol,and 9.59,respectively.The two-step sintering method under pressureless can achieve synergistic control of high relative density and fine grain.When the sintering process is set to 1430℃/1 h+1250℃/5 h,the relative density of PIM TiAl alloy reaches 96.3%with a lamellar colony size of about 100 μm.After hot isostatic pressing(HIP)treatment,nearly complete densification of the TiAl alloy is achieved,and the dimensional deviation and surface roughness Ra of the prepared swirlers are±0.1 mm and 1.046 μm,respectively.The room-temperature tensile strength,yield strength,and elongation of the HIP TiAl alloy are 577,466 MPa,and 0.96%,respectively.
TiAl alloyswirlerpowder injection moldingdimensional accuracysurface roughnessmechanical property
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