Characterization of two Ni-Cr dental alloys and the influence of casting mode on mechanical properties

• Published in: Journal of prosthodontic research Vol. 56; no. 4; p. 264
• Main Authors: Bauer, José, Costa, José Ferreira, Carvalho, Ceci Nunes, Grande, Rosa Helena Miranda, Loguercio, Alessandro Dourado, Reis, Alessandra
• Format: Journal Article
• Language: English
• Published: Netherlands 01-10-2012
• Subjects: Chromium Alloys; Dental Alloys; Dental Casting Technique; Dental Stress Analysis; Hardness; Materials Testing - methods; Tensile Strength
• ISSN: 2212-4632
• DOI: 10.1016/j.jpor.2012.02.004

The aim of this study was to evaluate the tensile strength, elongation, microhardness (MHV), composition and microstructure of two Ni-Cr based alloy, cast under different casting conditions.
Before casting, the alloy ingots were evaluated as regards composition (EDX) and microstructure (Optical microscopy, SEM and EDX). The casting conditions were as follows: electromagnetic induction in an environment controlled with argon (EWA), electromagnetic induction in an environment under vacuum (EWV), electromagnetic induction without atmosphere control (EWNC) and blowtorch (BT). For each condition, 16 specimens were obtained, each measuring 25 mm high and 2.5mm in diameter. The ultimate tensile strength (UTS) and elongation (EL) tests were performed in a Kratos machine (1.0mm/min). Fractured specimens were embedded in bakelite resin and polished for Vickers Microhardness analysis (1000 g/10s) with 4 penetrations in each specimen. The UTS, EL and MHV results were evaluated for two-way ANOVA and Tukey's test (α=0.05).
The cross-product interaction was statistically significant for all properties evaluated (p<0.0001), lower UTS, VHN and high elongation means were observed for the Ni-Cr-Mo-Be alloy tested when cast under the induction/argon (p<0.05). Higher UTS means were found for Ni-Cr-Mo-Ti alloy tested when cast under the induction/vacuum, and induction/air and flame/air condition (p<0.05). The two alloys show a microstructure with a dendritic formation with the presence of eutectic presence.
The Ni-Cr-Mo-Ti alloy showed high UTS, MHV and lowest EL comparaded with the tradicional Ni-Cr-Mo-Be, that show lowest UTS, MHV and higher EL when cast on induction/argon.