Metal working – Method of mechanical manufacture – Impeller making
Reexamination Certificate
1999-04-26
2001-03-06
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Impeller making
C029S889700, C250S458100
Reexamination Certificate
active
06195891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally directed at an improved method for detecting minute cracks in the surface of an article and automatically and/or manually repairing detected cracks, and specifically at detecting cracks in the surface of turbine engine hardware and automatically and/or manually repairing detecting such cracks with the aid of fluorescent penetrant.
2. Discussion of the Prior Art
In the course of engine operation, turbine engine hardware typically experiences minor damage as a result of engine operation. This damage can take many forms such as minor pits and cracks and may be as a result of any one of a number of conditions, such as ingestion of foreign particles, wear, erosion or fatigue. Frequently, the damage is of a minor nature, and after a repair operation, the hardware is suitable for reuse.
Currently, the articles to be repaired are visually inspected under suitable white light after cleaning so that defects or indications can be visually detected. In order to identify very fine cracks, visual inspection under magnification is conducted. As the cracks are identified by the operator, a suitable alloy in the form of a slurry is applied by the operator. The crack identification procedure and alloy application is the first step in well known repair procedures such as activated diffusion healing (ADH), partitioned alloy component healing (PACH) and brazing. After the application of the alloy, the articles are heated at elevated temperatures according to the selected procedure, ADH, PACH or brazing, which causes the alloy to flow and “heal” the defect.
After the repair procedure, the article is fluorescent penetrant inspected according to well-known procedures. These procedures require cleaning of the part, inspection of the part under an ultraviolet light, identification of any remaining defects, cleaning of the part and reapplication of the slurry for re-repair of any additionally identified defects. Of course, the problem with the procedure is that the subsequent fluorescent penetrant inspection frequently identifies defects that are not resolved or resolvable using the visual inspection techniques, with or without the aid of magnification. A process that can properly identify the defects present in the article prior to the repair cycle without adversely affecting the repair can save time, manpower, effort and energy resources if the entire repair can be completed in one cycle.
SUMMARY OF THE INVENTION
An improved method for identifying and repairing indications in the surface of articles is set forth by the present invention. The article that is to be inspected for reuse is first cleaned to remove any debris, oil, dirt or other foreign substances that could mask the indication. Fluorescent penetrant is then applied to the article. Once the penetrant is applied, the article is then visually inspected, under regular or “white” light without the aid of an ultraviolet light. This inspection reveals very large indications or defects, to which repair alloy is applied in the form of a slurry. After the manual application of the repair alloy, the article is then inspected with the aid of an ultraviolet light. The fluorescent penetrant in any fine cracks not filled with repair alloy as a result of the visual inspection under white light conditions are now revealed by the ultraviolet light. Additional repair alloy in the form of slurry is now applied to fill the additional cracks detected. The article is then subjected to the repair procedure, ADH, PACH or braze by exposing the article to an elevated temperature sufficient to cause the repair alloy to flow.
An advantage of the present invention is that all defects open to the surface of the part can be identified before repair by the combination of the inspection under white light and the inspection under ultraviolet light so that repair can be accomplished in one repair cycle. This greatly reduces the chance that defects such as cracks will be overlooked during the inspection process, as sometimes occurred in the two step inspection and repair process.
Another advantage to the present invention is that the slurry containing the braze alloy can be applied to defects such as cracks without removal of the fluorescent penetrant without adversely affecting the integrity of the repair.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
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Chen Keng N.
Hu Genfa
Cuda Rosenbaum I
GE Aviation Service Operation
Gressel Gerry S.
Hess Andrew C.
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