Investigation of the effect of ultrasonic vibration on the microstructure and mechanical properties of carbon steel in friction drilling process

The friction drilling process is a new process for producing cylindrical holes. In this process, a conical tool made of tungsten carbide is used and a bush is created along with a hole in the back of the part after drilling. The advantages of this new process include reducing drilling time and no chip production. In this paper, the friction drilling process is performed by combining ultrasonic vibrations. To perform the above process, a suitable ultrasonic horn was designed and made also a conical tool made of tungsten carbide with optimal angles was used for drilling. St37 steel material type was selected for workpiece. To investigate the effects of ultrasonic vibrations on the friction drilling process, micro-hardness tests, surface roughness test, corrosion test, and metallographic imaging (light microscope images and SEM images) were used. The results of this study indicated that the ultrasonic vibrations assisted friction drilling process increases the micro-hardness about 13 percent at special rotational speeds and vibrations intensities. Also, the corrosion resistance of the workpiece increased by about 57 percent in the case of applying vibrations of 96 W / cm2 intensity. According to the metallographic imaging, it was observed that the grain size and the amount of cavities of the workpiece are reduced due to the application of ultrasonic vibrations and these results is expressed qualitatively and comparatively.