EFFECTS OF FRICTION STIR PROCESSING ON MICROSTRUCTURAL, HARDNESS AND DAMPING CHARACTERISTICS OF FERRITIC NODULAR CAST IRON

Experimental investigations had been done in this study to explore the effects of friction stir processing (FSP) on the microstructure, hardness and damping capacity of fully ferrite nodular cast iron ASTM A536, grade 65-45-12. The main process parameters employed in this study were the rotational speed, translational speed and axial applied load which were varied within selected ranges. Their influence to be analysed and optimized for best process conditions compared with as cast material. Detailed investigations were carried out using optical microscopy, hardness test and impact test. Results showed that graphite grain refinements of 2-3 times the original size and phase transformations of a fully ferritic to bainite/martensite were achieved within the processed zone and across thickness. Matrix modifications caused improvement in hardness of 3.5 times compared to hardness of original cast iron. Increment in the damping capacity up to 14% was achieved. The stated improvements were related to the process parameters employed in the test.