Effect of casting technique on microhardness and microstructure properties of Co-Cr alloys used in fixed prosthetic dental treatment

Purpose: The purpose of this work was to investigate the effect of different casting methods on microstructure and microhardness of Co-Cr base alloys. Materials and Methods: Following the wax model preparation, 3 different methods were used for casting the test specimens consisting of 8mm high and 4mm diameter cylinders: 1) Acetylene-oxygen flame; 2) Electromagnetic induction/centrifugation; 3) Electromagnetic induction/vacuum injection. After the longitudinal sectioning of the specimens, surface preparation, polishing and chemical etching processes were carried out in order to observe the microstructure. The microstructure of the samples was examined by scanning electron microscopy. Vickers microhardness values were measured using a load of 2.94 N and a dwell time of 15 seconds. Results: The acetylene-oxygen flame casting showed higher microhardness values compared to induction/centrifugation and induction/vacuum injection molding. No difference was found between induction based casting methods. It was determined that Co-Cr base alloys show characteristic dendritic microstructure in all casting methods. Conclusion: Metallic substructures obtained by the acetylene-oxygen flame casting method have a higher microhardness than those obtained by electromagnetic induction based casting methods. The casting method has no effect on the microstructure of the alloys.