Experimental Research on Hole Wall Integrity of TiBw/TC4 Based on Ultrasonic Vibration Assisted Drilling

Abstract

Titanium Matrix Composites (TMCs) are widely used in aerospace because of their excellent mechanical properties, but it is accompanied by the difficulty of machining. Ultrasonic Vibration Assisted Drilling (UVAD) can effectively reduce the axial force in the drilling process and improve the integrity of machined surface. In this paper, the discontinuous titanium matrix composite TiBw/TC4 was developed by preparation method of in situ. In order to obtain the machining parameters of TiBw/TC4 and guide the application of UVAD in TiBw/TC4, the contrast experiments between conventional drilling (CD) and UVAD were carried out to analyze the variation law of axial force. In this experiment, the frequency and amplitude of ultrasonic vibration were set as 35 kHz and 2.5 μm respectively, and the drilling conditions were that the spindle speed was (1500/1600/1700/1800/1900) r/min and the feed speed was (6/7/8/9/10) mm/min. The surface integrity of hole wall such as roughness, residual stress and white layer was discussed. The experimental results show that the yield strength of TiBw/TC4 developed by in situ is 51% higher than that of pure TC4. Compared with CD, the axial force of TiBw/TC4 in UVAD is significantly reduced, and the formation of continuous chips and winding cutters is effectively reduced. Besides, the wear rate of the cutters is reduced. The number and size of hole wall defects, such as scratches, delamination and tearing, are obviously reduced. As well as the residual stress, white layer thickness and hole wall roughness are reduced by 4.67–16.31%, 42.48% and 5.98–29.27% respectively. Within the limits of the experiment, when the spindle speed is 1700 r/min and the feed speed is 8 mm/min, UVAD can obtain better hole wall surface integrity parameters.