High Speed Machining of Titanium Alloys

Removal rates for machining titanium alloys are an order of magnitude slower than those for aluminum. The high strength and hardness coupled with the relatively low elastic modulus and poor thermal conductivity of titanium contribute to the slow speeds and feeds that are required to machine titanium with acceptable tool life. Titanium has extremely attractive properties for air vehicles ranging from excellent corrosion resistance to good compatibility with graphite reinforced composites and very good damage tolerance characteristics. At current Buy to Fly ratios, the F-35 Program will consume as much as seven million pounds of titanium a year at rate production. This figure is nearly double that of the F-22 Program, which has a much higher titanium content. As much as 50% of the final cost of titanium parts can be attributed to machining. Specifically, in this task, we are working to improve the material removal rate of titanium to reduce cost. Lockheed Martin is evaluating the potential to use lasers to heat the material ahead of the tool to reduce its strength. Coupled with other technologies that can improve the tool life and prevent the titanium material from welding to the tool, there is hope for a practical solution using similar milling machines to those which exist today, if not a simple retro-fit option. This presentation will present the current progress of this project and its potential impact to the Joint Strike Fighter.