Abstract
An assessment has been made of the suitability of magnesia, calcia, alumina, and yttria for manufacturing melting crucibles and investment casting moulds for γ-TiAl alloys. Small refractory crucibles have been prepared by pressing or plasma spraying techniques and used to melt a small quantity of a Ti–48Al–2Nb–2Mn (at.-%) alloy in a carbon resistance furnace. The effects of the refractory type and melting time on the oxygen content, penetration, and microstructure have been established. The depth of penetration versus the holding time at 1550°C can be expressed by a power law. Based on these smallscale tests, it can be concluded that magnesia and silica containing alumina are unsuitable, whereas both pure calcia, yttria, and yttriacoated magnesia show promise for melting and casting γ-TiAl alloys.
Get full access to this article
View all access options for this article.