Abstract:
The present invention provides for a method of repairing a part, having a damaged portion that has deviated from an original configuration, by using a laser cladding process. The process comprises the steps of applying cladding material to the damaged portion, and irradiating the cladding material with the laser beam until such time as the cladding material substantially bonds with the part thereby forming a repaired area having a configuration substantially the same as the original configuration.

Description:
TECHNICAL FIELD  
       [0001]     The present invention is directed to a method of repairing a part and, more particularly, a method of repairing piston ring grooves using a laser cladding operation.  
       BACKGROUND  
       [0002]     Typically, an internal combustion engine commonly includes a crankshaft and a plurality of cylinders sized to receive a respective piston. A connecting rod couples each piston to the crankshaft. Each cylinder includes a combustion chamber that contains the high pressure gases formed during the combustion process of the fuel within the combustion chamber. To ensure that the combustion process occurs in an efficient manner, it is important that the interface of the piston and combustion chamber be sealed. This is typically accomplished by the use of one or more piston rings that are placed within piston ring grooves provided on the piston crown. Over time, the piston ring grooves will wear to a point that they are outside of design specifications. This wear can result in the loss of sealing of the combustion chamber thereby decreasing the efficiency of the combustion process.  
         [0003]     Those engine components that sustain damage or wear are oftentimes recycled or, as it is typically referred to, “remanufactured”. This assumes the component is not beyond repair and a suitable method to repair the component exists. Traditionally, repairing of the piston ring grooves was accomplished by machining the worn grooves so that they became larger than what the original specification called for. These “oversized” piston ring grooves then required “oversized” piston rings which may result in requiring different rings for the same piston. The use of different rings for the same piston could subsequently result in a mis-matching of the rings with the ring grooves during assembly and/or installing the wrong ring or rings.  
         [0004]     The present invention is intended to overcome one or more of the problems set forth above.  
       SUMMARY OF THE INVENTION  
       [0005]     In accordance with an embodiment of the present invention, a method of repairing a part, having a damaged portion that has deviated from an original configuration, by using a laser cladding process is provided. The process comprises the steps of applying cladding material to the damaged portion, and irradiating the cladding material with the laser beam until such time as the cladding material substantially bonds with the part thereby forming a repaired area having a configuration substantially the same as the original configuration. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a partial sectional view of a piston crown;  
         [0007]      FIG. 2  is a blown up view of that portion of that portion of the piston crown of  FIG. 1  comprising the ring grooves;  
         [0008]      FIG. 3  is a sectional view of ring grooves exhibiting wear characteristics;  
         [0009]      FIG. 4  is a diagrammatical view of a piston crown shown being repaired in accordance with the method of the present invention;  
         [0010]      FIG. 5  is a block diagram depicting a method of the present invention; and  
         [0011]      FIG. 6  is a sectional view of ring grooves which have been repaired in accordance with the teachings of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0012]     With reference now to the figures  FIGS. 1-3 , shown is a part such as the exemplary piston  100 , which includes a piston crown  101 , of the type used with internal combustion engines (not shown). Formed on the piston crown  101  and extending circumferentially thereabout are a plurality of ring grooves each denoted as  102 . Each ring groove  102  is sized to receive a piston ring (not shown) and each is separated from each other by a respective land  104 . With reference to  FIG. 2 , each piston ring groove  102  is bounded by an upper and lower face all designated herein as  200 . In  FIG. 2 , each ring groove  102  is shown in its substantially normal condition. In other words, the location of each face  200  is substantially where it would be if manufactured in accordance with the original specifications. In comparison to  FIG. 2 , shown in  FIG. 3  is a portion of the piston crown  101  in which the faces, each denoted as  300 , have experienced wear of a sufficient degree as to cause the faces  300  to recede from their original  FIG. 2  position.  
         [0013]     With reference now to  FIG. 4 , shown is a representative piston crown  101  in the process of being repaired in accordance with the teachings of the present invention. The piston crown  101  is shown coupled to a machine capable of rotating the piston crown  101  such as the laser cladding machine  400  shown. The laser cladding machine  400  may include a welding device  401  of the type utilizing a laser  404  such as, for example, a CO2 laser, that is placed adjacent to the piston crown  101  in such a manner as to allow the laser  404  to focus its beam  405  on that portion of the face  300  that is in need of repair. An example of a suitable laser clad machine is the Huffman HC-205 Five Axis Laser Powder Fusion Welder commercially available from Huffman Corporation (Clover, S.C.). A source of cladding material, denoted  408 , is provided to supply the material used to build-up those areas of the faces  300  that have receded. For those piston crowns  101  that are manufactured from steel, the cladding material may comprise an alloy steel powder or other suitable material. In addition, for the exemplary welding device  401  depicted herein, the welding device  401  is configured to feed the material directly into the beam  405  of the laser  404  thereby creating a bead  409  on face  300 . To prevent contamination of the bead  409 , a shielding gas  412  such as Argon is supplied to the area being clad.  
       Industrial Applicability  
       [0014]     With reference to the  FIG. 5  flowchart, block  500  depicts the initial step in the repairing of the piston crowns  101 . Each piston crown  101  is cleaned with a high pressure apparatus such as a blaster which uses ceramic beads or a baking soda/aluminum oxide mixture as the blasting medium. Next, the process moves to block  501  where the piston crown  101  is processed through a high pressure washer to remove any excess media remaining. After the initial cleaning process, the ring grooves  102  are measured to determine the need for repair, as depicted in block  504 .  
         [0015]     If it is determined that repair is needed (as depicted by decision block  505 ), the process then moves to block  508  where the faces  300  that are in need of repair are pre-machined, by using the above-identified laser cladding machine  400  or other like machine, a pre-determined amount, such as 0.020 inch, so as to provide for a uniform geometry of the face  300 . Prior to the laser cladding operation, the process proceeds to block  509  in which the piston crowns  101  are degreased to remove any remaining oil or contaminants.  
         [0016]     Once the pre-machining and cleaning is complete, the process proceeds to block  512  where the piston crown  101  is attached to the laser cladding machine  400  and the laser  404  is oriented to direct its beam  405  onto the face  300  in need of repair. For the exemplary process described herein, the diameter of the beam  405  is selected to be approximately 0.040 inches at a power level of approximately 1350 watts which has been found to be an acceptable power level in this application to provide sufficient fusion between the cladding material  408  and face  300 . The cladding material  408  is then fed into the beam  405  at a rate of approximately 3.45 grams per minute and the cladding material  408  and the face  300  are irradiated by the beam  405  for a length of time required to cause the cladding material  408  an the face  300  to bond together. Depending on the diameter of the piston crown  101  being repaired, the speed of the piston crown  101  in the laser cladding machine  400  should be selected to provide a cladding bead  409  of approximately 0.040 inches on the face  300 . During the cladding process, the shielding gas  412  such as Argon is supplied to the area being clad at a rate of approximately 1 cubic foot per minute. Additional beads  409  are then applied in such a manner as to be stacked on the preceding bead until the face  300  extends past the original specification location. In other words, the distance between the two faces  300  of a ring groove  102  are less than they were when the ring groove  102  was originally formed in accordance with the original specifications (e.g., the width of the ring groove  102  is less than the original width of the ring groove  102 ). When the face  300  has been built-up to a pre-determined amount, an additional pass with the laser  404  may be used to temper the repaired face  300 . An additional pass with the laser  404  to temper the heat effected area of the piston crow  101  may be performed at this time, either with or without cladding material  408 , using a predetermined wattage to achieve a proper temper.  
         [0017]     Once the laser cladding process is complete, the process proceeds to block  513  where the faces  300  that were repaired are again machined using the laser cladding machine  400  or other like machine to original print specifications. After this machining step, the process proceeds to block  516  where the piston crowns  101  are tested for any cracks using any suitable method such as, for example, magnetic particle testing. Finally, as shown in block  517 , the piston crowns  101  are again washed and any needed assembly, such as installing pin bushings (not shown), is completed. Shown in  FIG. 6  is a portion of the piston crown  101  showing the repaired areas of the ring grooves  102  comprising the new faces  600  formed in accordance with the teachings of the present invention.  
         [0018]     If it is determined that repair is not needed (as depicted by decision block  505 ), the process then moves to blocks  520 - 523  where the pistons  100  are, respectfully, cleaned, reassembled by installing new pin bore bushings (not shown), tested for cracks again using a suitable process such as a magnetic particle testing method, and finished washed.  
         [0019]     Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.