Effect of pin volume ratio on wear behaviour of friction stir processed LM25AA-5%SiCp metal matrix composites

Friction stir processing (FSP) technique is preferable over other conventional surface modification techniques because of its capability to produce relatively strong and defect free surfaces. However, there are certain parameters in FSP which have to be carefully optimized to obtain defect free surfaces with exceptional properties. From the previous findings, it was understood that the tool pin profile played an important role in determining the characteristics of the processed surfaces. Hence, it was decided to investigate the effect of pin volume ratio (PVR) on various regions of the processed surface. PVR is the ratio of dynamic volume to the static volume of tool pin. Dynamic volume is the volume of the profile generated by the tool pin when it is in motion. Static volume is the volume of the profile produced by the tool pin when it is at rest. The material displaced by the tool has to be in proper proportion with the volume occupied by the pin in static condition, in order to produce optimal surface properties. In this investigation, the tool with Taper cylindrical pin profile produced defect free surfaces with superior micro hardness and wear resistance compared to other tool pin profiles.