Interfacial reactions of cast titanium with mold materials

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Technology

Background:

• Titanium dental castings require high fidelity replication of complex shapes.
• Scale formation on titanium castings, due to high-temperature reactivity with investment materials, hinders this fidelity.
• Overcoming interfacial reactions is crucial for successful titanium casting.

Purpose of the Study:

• To evaluate the efficacy of stable oxide coatings on mold surfaces in minimizing interfacial reactions during titanium casting.
• To investigate the potential of oxide coatings as diffusion barriers to prevent scale formation.

Main Methods:

• Utilized traditional phosphate-bonded and commercial titanium investments for molds.
• Employed an experimental oxide coating (yttrium oxide or zirconium oxide) on mold surfaces.
• Performed pure titanium casting, followed by Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy analysis.

Main Results:

• Significant scale formation (7-10 microns) observed with traditional mold materials.
• Yttrium oxide and zirconium oxide coatings substantially reduced interfacial reactions between molten titanium and the investment material.
• Protective coatings acted as effective diffusion barriers, decreasing titanium-mold reactions.

Conclusions:

• Stable oxide coatings significantly reduce titanium-mold interfacial reactions in dental casting.
• Yttrium oxide particles, when applied without a binder, became entrapped in the titanium surface.
• Further research is necessary to develop an effective binder system for yttrium oxide coatings.