EFFECT OF DIFFERENT PREPARATION ROUTES ON COLOR METALLOGRAPHY OF ZIRCONIUM ALLOYS BY HEAT TINTING

So as to investigate the color metallography of Zirconium alloys via heat tinting method, different grades of this alloy such as Zircaloy-4, Zr-1% Nb, Zr-2.5% Nb has been applied as a base metal. For this purpose, each sample was prepared by different preparation routes such as polishing, polishing and etching, electropolishing. On the other hand, two important parameters (temperature and time) which play a significant role in the surface quality of specimens are considered in such a way that the surface of each sample is thermally etched at temperatures of 300 and 400ºC for 15 – 30 minutes. Results show that the best route for sample preparation is polishing and etching by using an electro-polishing apparatus. Outcomes show that the best temperature of heat tinting for different samples is about 400ºC and the best time is between 15 – 20 minutes. By comparison the optical microscopic images, it can be found that the heat tinting method is not suitable for samples with superplastic deformation microstructure while for annealed samples with equiaxed microstructure shows distinct images.