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Titanium alloy armor for combat vehicles has been successfully manufactured via plasma arc cold hearth melting (PAM) at a cost significantly lower than possible with current commercial processes.
Titanium and its alloys are frequently chosen for high-performance military components because of their low density, high strength, and good resistance to corrosion. However, high cost has prohibited their application in most army equipment. Nevertheless, in recent years the U.S. Army ground vehicle and weapons community has shown renewed interest in titanium, driven by mandates from the Pentagon to develop ground combat vehicles and weapons that are dramatically lighter than the current fleet. The new mandates open the door to consideration of titanium as the principal material of choice -- but only if available at affordable cost.
This is the genesis of the Manufacturing Technology program jointly managed by the U.S. Army Armament Research, Development, and Engineering Center (ARDEC) and the U.S. Army TankAutomotive Research, Development, and Engineering Center (TARDEC). The goal of this ManTech program is to achieve major cost reductions in titanium.
Titanium manufacturing
Emphasis on the development of plasma arc cold hearth melting (PAM) and electron beam cold hearth melting (EBM) is the result of efforts to reduce melt-related defects in premium quality titanium materials. Notably, Type I hard alpha (high interstitial) and high density inclusions are of concern. The primary application for high-grade titanium is for jet engine rotating components, and about 20% of the rotor-grade titanium alloys are required to be produced with either EBM or PAM as one of the production melt-steps. A helium atmosphere is required for PAM of titanium, whereas a vacuum is needed for EBM processing.
In contrast to the conventional vacuum arc remelting (VAR) process, both PAM and EBM have the potential of independently controlling the melting, refining, and casting steps. This unique feature permits PAM and EBM to remove detrimental inclusions, and it allows a variety of input materials as feed stock.
However, both technologies have drawbacks.
* Cold-shuts at the surface and helium entrapment within the ingots: These defects are exhibited in PAM-processed ingots produced by the current state-of-the-art technology. The PAM surface quality problem stems from the necessity to maintain enough fluidity in the molten titanium to enable it to flow to...