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Connection between the porous TiAl intermetallic compound and stainless steel

Author: ZhouQun
Tutor: HeYueHui
School: Central South University
Course: Materials Science
Keywords: porous TiAl intermetallic joining interface structure tensile strength
CLC: TG146.23
Type: Master's thesis
Year: 2008
Downloads: 168
Quote: 1
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Abstract


Porous TiAl intermetallic served as a brand-new promising porous material find wide use in filtration application. This dissertation reports an investigation of bonding porous TiAl intermetallic with SS （stainless steel） used as common structure components. Two bonding methods -adhesive bonding and brazing - were investigated. XRD, SEM, DSC were used to test the mechanical properties and interface structure.Adhesive bonding was an easy way to perform bonding porous TiAl with SS. The maximum tensile strength of joints at room-temperature is 47MPa.Porous TiAl was bonded well to SS using powder fillers by brazing, using Ti-50Cu as filler. Other 3 fillers were frustrated for following reasons: the maximum tensile strength of porous TiAl/Ti-25Ni-25Cu/SS joints at room-temperature was 35MPa, however, grain growth of porous TiAl caused by high brazing temperature resulted in reducing mechanical properties of porous TiAl; tensile strength of porous TiAl/Ti-25Cu/SS joint were low and could not be improved for lacking of liquid wetting; Cu-25Ti filler could corrode porous TiAl, and induced flaws at joints.Porous TiAl/Ti-50Cu/SS joint could perform easily and well. The influence of the processing temperatures, brazing times, heating and cooling rate was systematically examined. Tensile strength of joints was increased when highest brazing temperature were lifted（t=900s）, and maximum tensile strength was 47MPa; while t=60s-240s（T=950℃） tensile strength was increased, and t≥240s, tensile strength felt off. Maximum tensile strength was 65MPa for brazing 240s. Heating and cooling rate did not influence tensile strength much . These were the welding parameters that has optimized: brazing temperature was 950℃, brazing time was 240 seconds, and heating rate was 8℃/min, then cooling with furnace.The interface structure of the joint was porous TiAl/Ti3Al + Ti2Cu/TiCu+Ti2Cu/Ti-rich layer/Fe-rich layer/ SS. The oxidation resistance and corrosion resistance of optimized porous TiAl/Ti-50Cu/SS joint were investigated. The joints showed fine properties of oxidation resistance at 450℃, for tensile strength did not change much. While properties of oxidation resistance at 600℃was low, for tensile strength was 8MPa after 50h oxidation. Properties of corrosion resistance （ph=2 and ph=3） were studied, and corrosion pitting and selective corrosion of joint showed up.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys > Titanium
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