The aim of the present paper is to investigate the combined effect of mold material and binder for investment casting of titanium and titanium alloys. A plasma arc melting furnace was used for melting titanium alloy, and the interfacial reaction of titanium castings was determined by optical microscope, SEM, EDS analysis and hardness profile. The mold materials examined were ZrO 2 , Al 2 O 3 , CaZrO 3 and CaO. Machined graphite mold was examined for comparison. The result shows that the titanium castings produced using ZrO 2 and Al 2 O 3 mold had a clear reaction whereas a negligible reaction occurred in the castings in CaO, CaZrO 3 and graphite molds. CaZrO 3 is regarded as a promising mold material for titanium castings from the viewpoints of thermal stability against molten titanium alloy, sufficient mold handling strength and slurry viscosity control.
This paper describes the investment casting of TiAl alloys. The effects of mold material and mold preheating temperature for the investment casting of TiAl on metal-mold interfacial reaction were investigated by means of optical micrography, hardness profiles and an electron probe microanalyzer. The mold materials examined were colloidal silica bonded ZrO 2 , ZrSiO 4 , Al 2 O 3 and CaO stabilized ZrO 2 . When compared with conventional titanium alloy, the high aluminum concentration of TiAl alloys helps to lower their reactivity in the molten state. The Al 2 O 3 mold is a promising mold material for the investment casting of TiAl in terms of the thermal stability, formability and cost. Special attention need to be paid to thermal stability and mold preheating when developing the investment casting of TiAl alloys.
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