Evaluation of aging effect on different properties of Co-۲۵Cr-۶Mo-۰.۳C alloy

چکیده مقاله

The role of solution treatment and aging on the microstructure of Co-28Cr-5Mo-0.3C alloy was studied in the current research. Metallographic observations, scanning electron microscopy (SEM) and hardness measurements were used for evaluations. Results showed that the transformation of the metastable fcc phase to hcp phase during aging was extremely sensitive to the solution treatment prior to aging. The effect of increase of solution temperature and time was detectable through promotion of martensitic transformation during quenching in which hcp1 (straight bands) and hcp2 (lamellar-type constitution) phases developed. In contrast, low solution temperature and time led the most of the primary carbides to remain in undissolved condition in the matrix and accordingly during aging no sign of fcc to hcp1 (straight bands) phase transformation was obtained; although, formation of hcp2 phase (lamellar-type constitution) at the grain boundaries was observed. In addition, the X-ray diffraction pattern indicated that the sample solution treated at lower temperature and shorter time had more martensitic transformation during aging than the sample solution treated at higher temperature and longer time. Hardness measurements confirmed the results.