Niobium based alloy that is resistant to aqueous corrosion

Abstract

A niobium or niobium alloy which contains pure or substantially pure niobium and at least one metal element selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, Mo, W and Re to form a niobium alloy that is resistant to aqueous corrosion. The invention also relates to the process of preparing the niobium alloy.

Claims

1. A method of producing a niobium alloy that is resistant to aqueous corrosion, the method comprising microalloying pure or substantially pure niobium and at least one metal element selected from the group consisting of Ru, Rh, Pd, and Pt, wherein (i) the microalloying is performed to produce the niobium alloy via laser additive manufacturing (LAM), vacuum arc remelting (VAR), electron beam melting (EBM), or plasma arc melting (PAM), and (ii) each said at least one metal element is present, in the niobium alloy, in an amount less than its solubility limit in the pure or substantially pure niobium.

2. The method of claim 1, wherein the at least one metal element comprises platinum.

3. The method of claim 1, wherein the at least one metal element comprises ruthenium or rhodium or palladium.

4. The method of claim 1, wherein the at least one metal element comprises ruthenium and palladium.

5. The method of claim 1, wherein the at least one metal element comprises ruthenium.

6. The method of claim 1, wherein the at least one metal element comprises palladium.

7. The method of claim 1, wherein each said at least one metal element is present in an amount of at least 250 ppm in the niobium alloy.

8. The method of claim 1, wherein the microalloying is performed via laser additive manufacturing (LAM).

9. The method of claim 1, wherein the microalloying is performed via vacuum arc remelting (VAR).

10. The method of claim 1, wherein the microalloying is performed via electron beam melting (EBM).

11. The method of claim 1, wherein the microalloying is performed via plasma arc melting (PAM).

12. The method of claim 1, wherein, after the microalloying, the niobium alloy consists essentially of pure niobium and the at least one metal element.

13. The method of claim 1, wherein, after the microalloying, the niobium alloy consists of pure niobium and the at least one metal element.

14. The method of claim 1, wherein, after the microalloying, the niobium alloy consists of substantially pure niobium and the at least one metal element, the substantially pure niobium containing no more than 11% by weight of non-niobium components.

15. The method of claim 1, wherein, after the microalloying, the niobium alloy consists of substantially pure niobium and the at least one metal element, the substantially pure niobium containing no more than 5% by weight of non-niobium components.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 illustrates the conditions for the chemical processing industry that pure niobium will absorb hydrogen and become embrittled when exposed to hot HCl.

(2) FIG. 2 illustrates the conditions for the chemical processing industry that pure niobium will absorb hydrogen and become embrittled when exposed to hot H.sub.2SO.sub.4.

DETAILED DESCRIPTION OF THE INVENTION

(3) As used herein, the singular terms a and the are synonymous and used interchangeably with one or more. Accordingly, for example, reference to a metal herein or in the appended claims can refer to a single metal or more than one metal. Additionally, all numerical values, unless otherwise specifically noted, are understood to be modified by the word about.

(4) A niobium or niobium based alloy that is resistant to aqueous corrosion, more particularly to corrosion from acids and resistant to hydrogen embrittlement. The starting niobium is pure or substantially pure. Substantially pure niobium would be a niobium alloy which has up to about 11% by weight of non-niobium components, and preferably up to 5% by weight of non-niobium components.

(5) The niobium or niobium based alloys are preferably prepared using a vacuum melting process. Vacuum arc remelting (VAR), electron beam melting (EBM) or plasma arc melting (PAM) are methods of vacuum melting that can also be used for alloying. To formulate the actual alloy, at least one element selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, molybdenum, tungsten, and ruthenium (Ru, Rh, Pd, Os, Ir, Pt, Mo, W and Re) are added to the pure niobium material or substantially pure niobium material or niobium alloy using one of the vacuum melting processes listed above. Although it is noted that VAR, EBM or PAM could all be used. The preferred technique would be VAR.

(6) Alternative embodiments of this invention could include adding elements other than the elements listed above that improve the corrosion and hydrogen embrittlement resistance. These additional elements could include yttrium, gold, cerium, praseodymium, neodymium, and thorium.

(7) Each of the metals would preferably be less than 10,000 ppm of the alloy, preferably less than 5,000 ppm of the total amount of the alloy and more preferably less 2,000 ppm of the total amount of alloy. The metal preferably would be added in an amount of at least 50 ppm, preferably at least 100 ppm, preferably at least 150 ppm, preferably at least 200 ppm and preferably at least 250 ppm.

(8) The addition of ruthenium, palladium, or platinum would be the most preferred embodiment since these elements provide sites of low hydrogen overvoltage thereby stabilizing the Nb.sub.2O.sub.5 oxide layer.

(9) Another preferred embodiment would use the addition of rhodium, osmium, and iridium (also known as platinum group metals, PGM) which also would provide sites of low hydrogen overvoltage thereby stabilizing the Nb.sub.2O.sub.5 oxide layer.

(10) Still another preferred embodiment would use the addition of molybdenum since it has the same crystal structure, a similar lattice parameter, and complete solid solubility in both niobium and tungsten. This is shown in Table I and FIG. 1.

(11) TABLE-US-00001 TABLE I Crystal Structure and Lattice Parameters for Refractory Elements Lattice Element Symbol Crystal Structure Parameter () Niobium Nb body centered cubic (bcc) 3.301 Tungsten W body centered cubic (bcc) 3.16 Molybdenum Mo body centered cubic (bcc) 3.15 Platinum Pt face centered cubic (fcc) 3.931 Rhenium Re hexagonal close packed (hcp) a = 2.761, c = 4.458

(12) Another preferred embodiment would use the addition of rhenium since rhenium has the same crystal structure and a similar lattice parameter to niobium and tungsten.

(13) Niobium ingots formulated using VAR or PAM would then be used to produce plate, sheet, and tube products in a manner similar to that used to manufacture these same products from pure niobium or niobium alloy.

(14) The advantages of the new alloys would be superior corrosion and hydrogen embrittlement resistance over pure niobium. The addition of ruthenium, palladium, or platinum would be the preferred embodiment since these elements provide sites of low hydrogen overvoltage thereby stabilizing the Nb.sub.2O.sub.5 oxide layer.

(15) All the references described above are incorporated by reference in its entirety for all useful purposes.

(16) While there is shown and described certain specific structures embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described.