A comparison of corrosion resistance of cobalt-chromium-molybdenum metal ceramic alloy fabricated with selective laser melting and traditional processing.

STATEMENT OF PROBLEM: A cobalt-chromium-molybdenum alloy fabricated by selective laser melting is a promising material; however, there are concerns about the change in its corrosion behavior.

PURPOSE: The purpose of this study was to evaluate the changes in corrosion behavior of a cobalt-chromium-molybdenum alloy fabricated by the selective laser melting technique before and after ceramic firing, with traditional processing of cobalt-chromium-molybdenum alloy serving as a control.

MATERIAL AND

METHODS

Two groups of specimens were designated as group selective laser melting and group traditional. For each group, 20 specimens with a cylindrical shape were prepared and divided into 4 cells: selective laser melting as-cast, selective laser melting fired in pH 5.0 and 2.5, traditional as-cast, and traditional fired in pH 5.0 and 2.5. Specimens were prepared with a selective laser melting system for a selective laser melting alloy and the conventional lost wax technique for traditional cast alloy. After all specimen surfaces had been wet ground with silicon carbide paper (1200 grit), each group of 10 specimens was put through a series of ceramic firing cycles. Microstructure, Vickers microhardness, surface composition, oxide film thickness, and corrosion behavior were examined for specimens before and after ceramic firing. Three-way ANOVA was used to evaluate the effect of porcelain firing and pH values on the corrosion behavior of the 2 alloys (α=.05). Student t tests were used to compare the Vickers hardness.

RESULTS

Although porcelain firing changed the microstructure, microhardness, and x-ray photoelectron spectroscopy results, it showed no significant influence on the corrosion behavior of the selective laser melting alloy and traditional cast alloy (P>.05). No statistically significant influence was found on the corrosion behavior of the 2 alloys in different pH value solutions (P>.05).

CONCLUSIONS

The porcelain firing process had no significant influence on the corrosion resistance results of the 2 alloys. Compared with traditional cast cobalt-chromium-molybdenum alloy, selective laser melting alloy exhibited the same properties in both test solutions (pH, 5.0 or 2.5).