Microstructural Evaluation and Strain Life Behavior of Friction Stir Processed Ferritic Nodular Iron

Investigations had been performed to demonstrate the effects of Friction Stir Processing (FSP) on the microstructure, hardness and strain life of fully ferrite nodular cast iron ASTM A536, grade 65-45-12. The processing tool is a 20 mm diameter cylindrical pinless tool made of tungsten carbide. Processing parameters, which are: rotational speed, translational speed and applied load, were employed and scheduled in this evaluation. Results showed that maximum graphite grain refinements of 2-3 times and phase transformations of a fully ferritic to bully’s eye, pearlite/bainitite and bainite/marensite were achieved within the processed zone and in depth of processed specimens. These modifications in microstructure caused significant improvements of the processed surface hardness 100 to 300% and strain life of 9 to 65% depending on the process parameters (rotation speed, feed speed and applied load).