Experimental study on deep-hole making in Ti-6Al-4V by abrasive water jet machining

Abstract

Ti-6Al-4V alloy possesses high strength to weight ratio, outstanding corrosion resistance, poor machinability and has versatile range of applications in aerospace, automotive, medical and other major industries. This study presents machining of deep holes of nominal diameter 3 mm with depth of 100 mm in Ti-6Al-4V by AWJM. The aim of this study is to analyse the hole quality characteristics and its surface morphology. The holes were drilled with jet pressure of 309 MPa, stand-off- distance of 2 mm and abrasive flow rate of 289 g min−1. The surface qualities of machined sections were analysed using surface roughness tester. SEM technique was used to investigate the surface morphology. It was found that at 14 min the jet pierced the hole; however, on just piercing, the hole was found to be conical with smaller diameter at the exit side of the jet. On further increase of the machining time the hole got corrected. A fairly uniform diameter hole through the thickness was obtained on additional machining for about 3 min 30 s. The surface roughness (Ra) at the bottom was 1.60 μm on piercing and 1.27 μm after hole correction. It was found that the surface roughness gets decreased by 25% after the hole correction process. Scanning electron microscopic images revealed that the mechanism of material removal at the bottom and top sections of the hole differed until piercing the hole whereas after hole correction process an aligned shallow ploughing pattern was seen on top, middle and bottom section of hole.