Investigation of effects of some metals on cobalt based alloys

Effects of V, Ti, and Mn additions on microstructure and mechanical properties of a cobalt based cast alloy have been investigated in this study. Co-28Cr-6Mo-0.7Mn-0.5Si-0.5C alloy, which is the most common cobalt based alloy used for dental applications, was taken as reference, and 1,3 % Mn, % 0,7-2,0 Ti; % 0,7-1,3 V was added to produce six different alloys. Alloying elements were added to cobalt based alloy by melting in an induction furnace under normal atmospheric conditions. 99.9 % pure elements were used for alloying process.The melt was die cast into preheated metal dies as bars. Specimens were extracted from these casts for mechanical tests, microstructural analysis, and X-ray diffraction. From the mechanical tests, the hardness of cobalt based alloys were seen to have decreased with Mn and V addition. Ti addition decreased the hardness until a certain rate, but increased in excess. Microstructural analysis showed that the original alloy had dendritic structure. On dendrite arms nano-sized region was taken from. With Mn edition dendritic structure in reference alloy was dispersed homogenly. With Ti addition have been observed that dendrite structure was existed but nano-sized dendritic structures disappear completely. With Vaddition nano sized dendrite structure was appeared again and ıtwas seen that this nano dendrite arms wre longer than referance alloy.X-ray diffraction studies showed that M23C6, Mn15C4, TiSi2, VSi2 etc. phases were occurred in materialsKeywords: Cobalt; Cobalt based alloys; Biomedical materials; Nanferrous alloys