Media mixture for improved residual compressive stress in a product

Abstract

A media mixtures is disclosed for imparting compressive residual stress on a work piece in a high energy centrifugal processor. The media mixture includes carrier media, preferably made from a fractured grain product. The carrier medium having an average size of at least about 0.05 inches and a hardness. A plurality of abrasive particles are mixed with the carrier media, Each particle has a size that is smaller than the carrier medium and has a hardness that is greater than the hardness of the carrier medium.

1 . A media for imparting compressive residual stress on a work piece in a high energy centrifugal processor, the media comprising: 
 a plurality of carrier medium, each having an average size of at least about 0.05 inches, and a hardness; and    a plurality of abrasive particles, each particle having a size that is smaller than the average size of the carrier media and having a hardness that is greater than the hardness of the carrier media.    
   
   
       2 . A media according to  claim 1  wherein the size of the particles is approximately 1000 grit.  
   
   
       3 . A media according to  claim 1  wherein the carrier medium has a size of between about 0.05 inches and about 0.50 inches.  
   
   
       4 . A media according to  claim 4  wherein the carrier medium is made from a grain product.  
   
   
       5 . A media according to  claim 1  wherein a plurality of the abrasive particles are attached to each carrier medium.  
   
   
       6 . A media according to  claim 5  wherein on average at least 50% of the surface area of each carrier is coated with abrasive particles.  
   
   
       7 . A media according to  claim 5  wherein the abrasive particles are attached to the carrier medium with a lubricant.  
   
   
       8 . A media according to  claim 1  wherein at least some of the abrasive particles are selected from a group consisting of aluminum oxide, silicon carbide, tungsten carbide and diamond.  
   
   
       9 . A media according to  claim 1  further comprising a plurality of solid additives in the media, the solid additives each having a size that is larger than the abrasive and a density greater than the carrier medium.  
   
   
       10 . A media according to  claim 9  wherein the solid additives are substantially spherical in shape.  
   
   
       11 . A media according to  claim 1  wherein the grain has a weight of between about 15 and 35 pounds per cubic foot of weight per volume.  
   
   
       12 . A process for preparing a media mixture for use in a centrifugal processing machine for processing a part, the process comprising the steps of: 
 providing carrier media made from fractured grain product, the fractured grain having an average size of greater than about 0.05 inches;    providing abrasive media having a size of at least 1000 grit; the amount of abrasive media being selected to coat on average at least about 50% of the carrier media; and    mixing the media together to form a mixture.    
   
   
       13 . A process for preparing a media mixture according to  claim 12  further comprising the step of adding an adherent into the mixture to cause a plurality of the abrasive media to adhere to the carrier media.  
   
   
       14 . A process for preparing a media mixture according to  claim 13  wherein the adherent is a lubricant.  
   
   
       15 . A process for preparing a media mixture according to  claim 12  further comprising the steps of: 
 providing a plurality of metallic additives, each additive having a density greater than the density of an average carrier medium; and    adding the metallic additives to the mixture of the abrasive media and the carrier media.    
   
   
       16 . A process for preparing a media mixture according to  claim 15  wherein the additives are metallic balls.  
   
   
       17 . A process for preparing a media mixture according to  claim 12  wherein the abrasive particles are selected from a group consisting of aluminum oxide, silicon carbide, tungsten carbide and diamond.  
   
   
       18 . A process for preparing a media mixture according to  claim 12  wherein the carrier medium has an average weight of between about 15 and 35 pounds per cubic foot of weight per volume.