A metallurgical study of the contamination zone at the surface of dental Ti castings, due to the phosphate-bonded investment material: the protection efficacy of a ceramic coating

摘要

Titanium casting procedure shows some seriousdifficulties related mainly with its high melting point and its greatchemical reactivity at high temperatures. As a result, an extensivecontamination is observed in Ti castings when SiO2-basedinvestment materials are used (phosphate-bonded or silica-bonded).In the present work, a detailed metallurgical study of thecontamination zone of Ti castings due to Si, P and O, wasperformed. The new phases which formed, were investigated andanalyzed using mainly light and scanning electron microscopy, aswell as energy dispersion spectrometry. These phases were foundto be:α-Ti, β-Ti and Ti-Si compound. An attempt was done toprevent the contamination of cast Ti by using a wax pattern coatingtechnique. The protection efficacy of a ZrO2 coating was proven.Ti castings without contamination were obtained in this way.