Examples of tantalum alloys with a tantalum content of at least 89% include, but are not limited to, Ta-3W(tantalum-tungsten) containing at least about 3% tungsten, Ta-3W-Pt (tantalum-tungsten and platinum alloy) containing at least about 3% tungsten, Ta-3W-Mo (tantalum-tungsten and molybdenum alloy) containing at least about 3% tungsten, and Ta-3W-Re containing at least about 3% tungsten Tantalum-tungsten and rhenium alloy. Ta-3W-Pt, Ta-3W-Mo, and Ta-3W-Re can be formulated and manufactured in a manner similar to the preparation of Ta-3W. Alloys are preferably prepared by microalloying other metals with Ta-3W(tantalum-tungsten) alloys.
The addition of platinum is the most preferred embodiment because platinum has the most free electrons and could theoretically attract additional oxygen atoms to close the holes in the Ta2O5 oxide layer and/or provide sites with low hydrogen overvoltage, thus stabilizing the Ta2O5 oxide layer.
Another preferred embodiment is the addition of ruthenium, rhodium, palladium, osmium, and iridium (also known as "platinum group metals", i.e., PGMS), which also provide low hydrogen overvoltage sites to stabilize the Ta2O5 oxide layer.
Another preferred embodiment is the addition of molybdenum, as it has the same crystal structure, similar lattice parameters, and complete solid solubility in tantalum and tungsten.
Sheet and tube products made of Ta-3W-Mo, Ta-3W-Re or Ta-3W-Pt alloys are used in the same manner as those made of pure tantalum or Ta-3W alloys.
The advantages of the new alloy over pure Ta-3W are its excellent corrosion resistance and hydrogen brittleness resistance. Adding platinum is the most preferred embodiment because platinum has the most free electrons and theoretically attracts additional oxygen atoms, helping to seal holes in the Ta2O5 oxide layer and/or providing sites with low hydrogen overvoltage, thereby stabilizing the Ta2O5 oxide layer.
