Mechanical and microstructural properties of a nickel-chromium alloy after casting process

Resumo

There is a growing concern on the development
of adequate materials to interact with the human body. Several
researches have been conducted on the development of biomaterials
for dental applications. Objective: This study aimed to determine
the microstructural and mechanical properties of a nickel- based
alloy, after the casting process. Material and methods: The alloy
was melted through lost wax technique and centrifugation, by
using blowtorch with liquefied petroleum gas. To evaluate the
mechanical properties, tensile bond strength and microhardness
tests were performed. The microstructural characterization was
performed using scanning electron microscopy (SEM) and energy
dispersive spectroscopy (EDS). Statistical analyses were performed
on microhardness results, through Student t test. A program for
digital image processing was used to determine the percentage of the
existing phases. Results and conclusion: The tensile strength was
higher than that reported by the manufacturer, 559.39±25.63MPa
versus 306 MPa, respectively. However, the yield strength was
slightly lower, 218.71±29.75 MPa versus 258 MPa, reported by the manufacturer. The microhardness tests showed about 70 HV, far
above the value informed by the manufacturer (21 HV). It can be
affirmed with 95% confidence interval that the casting process did
not alter the material’s hardness. The alloy’s microstructure is formed
by a matrix with dendritic aspect and gray color and a second white
interdendritic phase with equally distributed precipitates as well as
porosities. EDS tests showed that the matrix is rich in nickel and
chromium, the interdendritic second phase is rich in molybdenum
and the precipitates in titanium or silicon. The matrix represents
86% of the area and the second phase 12%.