Electrolysis: processes – compositions used therein – and methods – Product produced by electrolysis involving electrolytic...
Patent
1994-08-31
1996-09-24
Niebling, John
Electrolysis: processes, compositions used therein, and methods
Product produced by electrolysis involving electrolytic...
205109, 205110, 205228, 205319, 427304, 427437, 428614, 428668, 428679, 428935, C25D 1500
Patent
active
055587585
DESCRIPTION:
BRIEF SUMMARY
This invention relates to electrodeposited composite coatings, i.e. coatings which consist of an electrolytically or electrolessly plated metal matrix with included particles which are codeposited with the matrix. The particles are suspended in the electrolyte containing the metal ions for the matrix and are substantially insoluble in the electrolyte and, during the plating operation, become included in the plated matrix.
The coatings may be applied to a variety of components subjected to wear such as aero-engine components, particularly those likely to operate at elevated temperatures, bearing surfaces, rocket nozzles, and tubes and nozzles carrying abrasive substances. The coatings may be applied to the whole component but more frequently they will be applied to only a portion of its surface. The electrodeposition technique is particularly suitable to the protection of selected areas and the coating of complex, re-entrant and inaccessible areas do not present any great problems. The coatings are particularly suited to use on gas turbine blades.
Our United Kingdom patent GB-A-1358538 describes a composite coating comprising, as deposited, a matrix which is at least 50% by weight cobalt and particles included in the matrix which are at least 50% by weight chromium carbide, at least 50% by weight of the particles having a particle size of less than ten microns and preferably between 2 and 5 microns.
The specification of GB-A-1358538 indicates that although preferably all the particles have a size between 2 and 5 microns it may not be practicable completely to avoid a small quantity of fines below 2 microns and possibly some larger particles due, for example, to agglomeration but states that preferably more than 80% by weight of the particles lie within the specified limits, i.e. between 2 and 5 microns.
The processes described in GB-A-1358538 have been used for approximately twenty years with very great success. The particles which have been used have had a size distribution within the range set out, i.e. most of the particles having a size between 2 and 5 .mu.m. The particles used have been much as received from the supplier but, as will be explained below, some small adjustment has sometimes been made by removing a proportion of the larger particles. It has been found that coatings are produced having an as-deposited composition range of between 13 and 20 percent by weight of chromium carbide dispersed in a cobalt matrix. The as-deposited coatings are somewhat modified by diffusion produced by heat treatment and/or heat resulting from use of the components carrying the coatings. These coatings perform well under rubbing/ fretting wear conditions where the pressure-velocity (PV) values are moderate. It would be advantageous for the properties of the coatings to be improved so that they can operate at higher PV values and in conditions involving hammer or impact forces. It is felt that a more robust coating could be obtained if the weight fraction of carbide particles could be increased. It has now been discovered that the fraction of carbide particles in the as-deposited coating can be increased to a very surprising degree by providing for most of the particles to fall within the size range of 4 to 12 .mu.m and preferably with a mean size of 7 .mu.m. Preferably 80% and more preferably 90% by weight of the particles are within the 4 to 12 .mu.m range. By mean size is meant that half the particles by weight have a size less than 7 .mu.m and half have a size equal to or larger than 7 .mu.m. Alternatively, the invention may be said to reside in using particles at least 80% by weight of which exceed 4 .mu.m in size and at least 80% of which lie within a range of 4 .mu.m to 8 .mu.m (and preferably with the upper end of the range not exceeding 20 .mu.m). Preferably, the particles are substantially evenly distributed in size across the range.
The invention also includes, according to a further aspect, a method of producing a coating comprising depositing by electrodeposition or by electroless deposition a matrix o
REFERENCES:
patent: 3532608 (1970-10-01), Serra
patent: 4789441 (1988-12-01), Foster et al.
Denninger Douglas E.
Hansra Tejpal S.
Niebling John
Praxair S.T. Technology, Inc.
Wong Edna
LandOfFree
Electrodeposited composite coatings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrodeposited composite coatings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrodeposited composite coatings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1926472