AWJ Milling of Gamma Titanium Aluminide

Abstract

A study was undertaken to determine the feasibility of the AWJ process for controlled depth milling of gamma Titanium Aluminide tiles. It was demonstrated that milling can be accomplished to 0.025-mm accuracy. To overcome undercutting near rib roots, the jet was clock-angled at about 15 degrees to the vertical every set of passes. This allowed the milling to thin skins of about 0.5-mm. It was observed that as the material is milled, stresses were relieved and either deformation or cracking may result. Accordingly parts need to be annealed before milling. The milling to thin skins was successfully demonstrated on 150mm × 300-mm parts without adverse effects. Also, the process of milling of dual rib height was developed using dual mask approach. Abrasive particle embedding on the milled surfaces was observed to be about 0.15% of the area, but cleaning with plain waterjets showed that all embedded particles can be removed. A detailed economic analysis confirmed that the AWJ milling process is relatively inexpensive and highly productive. The complete cost of milling including mask cutting, overhead, capital, and running cost is less than $300/ft2.