Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing inorganic compound
Patent
1997-04-15
1998-07-07
Gorgos, Kathryn L.
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing inorganic compound
205560, 205687, 205704, 205766, 205767, 423 49, C25B 100, C25C 100, B01D 1706, C01G 4500
Patent
active
057763291
DESCRIPTION:
BRIEF SUMMARY
This is a National stage application of PCT/E095/04177 filed Oct. 10, 1995.
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a method for the decomposition of superalloys and subsequent recovery of the alloying metals. The method comprises two steps.
Superalloys are alloys which are based on cobalt or nickel and which may contain a whole series of additional elements such as, for example, aluminium, chromium, hafnium, molybdenum, platinum, tantalum and tungsten. There is a good survey of the prior art relating to the composition and characteristic properties of superalloys in the Kirk-Othmer Encyclopedia of Technology, Volume 12, Fourth Edition, pages 417-458.
In contrast to normal alloys, superalloys are not attacked in oxidising and corrosive environments. According to Swiss Material 1990, 2, 5-10, owing to their resistance to oxidation, components made of superalloys find application, for instance, as blades in aircraft turbines.
The decomposition and recovery of the alloy metals in the superalloys is of economic interest because of the relatively high precious metal content of some superalloys. Thus in special superalloys, for example, rhenium is found in a proportion of up to 6% by weight. Moreover other alloying constituents, such as, for example, platinum, tantalum, tungsten, molybdenum, are also useful metals.
According to prior art, in order to recover the metallic constituents from the superalloy, the latter is melted and atomised to a fine-particled powder in an atmosphere of protective gas. The powder is then decomposed in concentrated acid and further processed. This method of procedure is unsatisfactory, as superalloys melt only at relatively high temperatures of between 1200.degree. C. and 1400.degree. C. In addition the entire melting and atomising process must proceed in an inert atmosphere of protective gas, because otherwise some metals will instantly form oxides which are volatile and moreover hazardous to health. (Thus, for example. rhenium(VII) oxide has a boiling point of 360.degree. C.). The actual melting takes place only in the atomised powder in concentrated acid and, according to experience. requires several days.
From the Journal of Applied Electrochemistry 1977, 7, 1-29, it is known that hard workpieces made of metal or alloys can also be processed by electrochemical oxidation in aqueous electrolyte solutions. This method of procedure is generally known by the term `electrochemical machining` or `electrochemical grinding` and is employed in the production of complex components. Superalloys can also be processed by this electrochemical method. But the method is unsuitable for the decomposition and recovery of alloying constituents, as the reaction products cannot be worked up and separated satisfactorily. Anodic oxidation in aqueous solutions gives rise to the preferential formation of hydroxides and oxides which cannot be filtered easily.
It should also be taken into consideration that through anodic oxidation many alloys form a dense oxide layer which is impermeable to an electric current and effectively prevents further oxidation of the alloy. These very robust passivating layers can be broken through only at very high electrolytic voltages of 50 volts and above. Because of this an electrochemical method in aqueous electrolytes is of no interest economically.
SUMMARY OF THE INVENTION
The object of the present invention was therefore to provide a method for the decomposition and recycling of alloying constituents from alloys, which can be carried out easily and economically. This object was fulfilled by electrochemical oxidation of the alloy in an organic electrolyte and subsequent separation of the alloying metal by a chemical separation process.
The present invention therefore provides a method for the decomposition of superalloys and subsequent recovery of the alloying metals by a wet chemical method, with the decomposition being carried out electrochemically. The method according to the invention can be applied in particular to superalloys cont
REFERENCES:
patent: 3348942 (1967-10-01), Davenport
patent: 4278641 (1981-07-01), Petrov et al.
patent: 4298581 (1981-11-01), Douglas et al.
patent: 4557906 (1985-12-01), Douglas et al.
patent: 4599222 (1986-07-01), Douglas et al.
patent: 4604265 (1986-08-01), Douglas et al.
patent: 5442910 (1995-08-01), Anderson
Bannard, J., Electrochemical Machining, 7 J. Appl. Electrochem. 1 (1977). no month available.
Kirk-Othmer, Encyclopedia of Chemical Terminology, 4th ed., vol. 12, pp. 417-458. date unavailable .COPYRGT.1994.
Bannard, "Electrochemical Machining", J. of Appl. Electrochem., vol. 7, pp. 1-29, 1977.
Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed., vol. 12, pp. 417-458, 1994.
Krynitz Ulrich
Kummer Wolfgang
Olbrich Armin
Schloh Martin
Bayer AG
Cohen Jerry
Gorgos Kathryn L.
H.C. Starck GmbH & Co KG
Wong Edna
LandOfFree
Method for the decomposition and recovery of metallic constituen does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the decomposition and recovery of metallic constituen, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the decomposition and recovery of metallic constituen will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1201690