Cutting costs of titanium powder

Tag : Titanium Alloys
A new processing technique could reduce the cost and the amount ofenergy required to make titanium parts from powders by up to 50 percent claim its developers.

This means titanium alloys could be made more cheaply forapplications such as brake rotors, artificial joint replacementsand armour for military vehicles.

Bill Peter, one of the developers of the process at the Oak Ridge National Laboratory (ORNL) in the US, said instead of using conventional meltprocessing to produce products from titanium powder, his group andseveral industry partners have developed a method that allowspowders to remain in their solid form during the entire process.

'This saves a tremendous amount of energy, greatly reduces theamount of scrap and allows for new alloys and engineeredcomposites,' he said.

The powder metallurgy process has been used to produce componentsfor many years. However, titanium products have not widely beenfabricated using these methods because of the high cost ofconventional titanium powders.

To get powder metallurgy grade titanium powder, titanium must gothrough a hydride-dehydride (HDH) process or it has to be atomisedby gas. Both of these methods produce powders that are expensive.

However, new low-cost titanium powders have enabled ORNL to developthese technologies for titanium.

The organisation has relied on the expertise of DARPA's TitaniumInitiative Programme (DTI), which has developed methods thatproduce low-cost titanium powder at purity levels sufficient forpowder metallurgy.

International Titanium Powder, one of DARPA's DTI project partners,developed a process that involves injecting titanium tetrachloridevapour into a stream of molten sodium. This causes a reaction tooccur between the titanium tetrachloride and the sodium to producetitanium powder. With simple modifications of the process, it isalso possible to make vanadium/aluminum titanium alloys.

Peter said the process runs at relatively low temperatures, doesnot require additional purification and produces high purity powdersuitable for metallurgical processes with no waste.

The powder can then be used to produce net shape components with avariety of non-melt techniques, such as cold roll compaction ofmetal powder in a continuous sheet or coil.

This method has been used commercially for many years, but untilrecently titanium had not been commercially produced this waybecause of the high cost of conventional titanium powder.

The researchers at ORNL demonstrated that the low-cost titaniumpowder would work just as well as other metals with this technique.The team fed titanium powder through two counter-rotating rollers.The compressive stresses between them consolidated the materialinto continuous sheet.

The sheet was sintered and cold rolled to achieve full density andthen softened by heat to acquire the desired microstructures andproperties.

The ORNL team worked with the Department of Energy, the Departmentof Defence's Advanced Research Projects Agency and BAE Systems todemonstrate how the new powder could be used to produce a newlow-cost titanium alloy door for the Joint Light Tactical Vehicle,a next-generation combat vehicle.

'By using a titanium alloy for the door, BAE Systems was able toreduce the weight of its vehicle while at the same time decreasingthe threat of armour-piercing weapons,' said Peter.

The lightweight titanium alloy is also claimed to improve theoperation of the door and increases mobility of the vehicle, makingit even more useful to the military.

In the future, Peter and his colleagues expect lightweightcorrosion-resistant titanium alloys to make their way into manyother products, such as cars, which could benefit from thedecreased weight and, he said, will be able to deliver improvedfuel economy.