Process for electrochemical decomposition of superalloys

Abstract

A process for recovery of valuable metals from superalloys by electrochemical decomposition is described, both electrodes being formed by the superalloy and the polarity of the electrolysis current being reversed with a frequency of from 0.005 to 5 Hz.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to a process for electrochemical decomposition of superalloys, in particular superalloy scrap, with the particular purpose of recovering rare and valuable metals such as rhenium, platinum, tantalum and hafnium.[0003] 2. Brief Description of the Prior Art[0004] Superalloys are high melting, high strength and extremely wear-resistant alloys of a comparatively large number of metals, which are used predominantly in turbine construction, especially aircraft turbines. Their special properties are owed in part to the addition of very rare and expensive elements, for example tantalum, hafnium or even rhenium / platinum. Because of their tough nature, it is difficult to recycle them, and to date they are not recycled economically, after their service life.[0005] This has led to irretrievable loss of these high value, strategic raw materials with limited availability, owing to fusion of the said superalloy scrap into normal s...

AI Technical Summary

Problems solved by technology

Because of their tough nature, it is difficult to recycle them, and to date they are not recycled economically, after their service life.

This has led to irretrievable loss of these high value, strategic raw materials with limited availability, owing to fusion of the said superalloy scrap into normal steels, on the order of, for example, up to 10 t / a (tons per year) of rhenium and 30 t / a of tantalum.

Hence the lack of recycling constitutes a waste of resources not only in economic terms but also in terms of the "responsible care" concept adopted by the chemical industry.

At any rate, because of the explosive development of the electronics industry, requiring constantly increasing demand for tantalum, the supply of this raw-material is becoming ever weaker.

While there are a number of pyro- and hydrometallurgical approaches for recovering the metallic constituents of superalloys, they are not economically suitable because of their cost-intensive complexity or their time-consuming nature.

For example, it is known to melt superalloys under a protective-gas atmosphere, subsequently spray the melt to form a finely divided powder, and then decompose the powder by using a time-consuming treatment with inorganic acids.

It would also be conceivable to comminute superalloy-part scrap after prior suitable embrittlement by elaborate grinding processes, but this would be just as expensive.

Regarding this recycling of Ni, Co or copper, there is a lack of any information about current, current density, anodic / cathodic current efficiency, precise electrolyte composition, completeness of the separation, as well as estimable space-time yields or information about economic viability.

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