A new strategy for improving the surface quality of Ti6Al4V machined by abrasive water jet: reverse cutting with variable standoff distances

Abstract

Titanium alloys are widely used in important structures of aerospace vehicles, but the low thermal conductivity and high chemical activity make them difficult to process. As an untraditional machining technology, abrasive water jet (AWJ) has been proven to be an effective method for this kind of material. Aimed at further improving the cutting performance, reverse cutting with variable standoff distance (SOD) strategy was put forward, and experiments of titanium alloy Ti6Al4V machined by AWJ were conducted. The influence of SOD with different reverse cutting types on the kerf quality was studied, and the total height of the surface (St), the arithmetical mean deviation of the profile (Ra), the arithmetic mean and root-mean-square deviations of the surface (Sa, Sq), and the kerf taper (α) were used to evaluate the cutting quality. It was found that the proposed strategy could result in a higher machining quality compared with the single cutting. More specifically, for the reverse trimming cutting, the highest of the striations characterized by St could be reduced from 341 to 117 μm at traverse speed of 600 mm/min using this strategy. The improvements of Ra, Sa, and Sq can reach up to 62.8%, 67.0%, and 57.2%, respectively, under the condition that the SOD of the second cutting is 8 mm. Furthermore, the kerf taper can be reduced 26.1% at SOD of the second cutting being 2 mm. With respect to the reverse deepening cutting, even the traverse speed of reverse cutting is set as twice as that of a single cutting, the kerf quality is still better. Additionally, when the SOD of the second cutting is 4 mm, the improvements of Ra, Sa, and Sq can reach up to 51.7%, 34.3%, and 33.2%, respectively, and at the same time, the kerf taper is reduced by 20.2%.