Enhanced Blade Tipping For Improved Abradability

Abstract

An abrasive coating comprising a plurality of first grit particles placed on a top surface of a substrate and spaced to provide channels for the removal of cut chips and rub debris and heat reduction. A plurality of second grit particles are placed between each of the first grit particles, and having a nominal size smaller than the first grit particles. A mixture of the second grit particles to the first grit particles comprises from about 75-98%. The second grit particles form a single layer or multiple layers and comprise height of 10 to 60% of that of the first grit particles. A matrix material is bonded to the top surface; the matrix material envelops the second grit particles and bonds to and partially surrounds the first grit particles. The first grit particles extend above the matrix material and the second grit particles relative to the top surface.

What is claimed is: 
     
         1 . An abrasive coating for a substrate, comprising:
 a plurality of first grit particles adapted to be placed on a top surface of said substrate, wherein said plurality of first grit particles are spaced to provide channels for at least one of the removal of cut chips and rub debris and the reduction of heat generation;   a plurality of second grit particles placed between each of said plurality of first grit particles, said second grit particles having a nominal size smaller than said first grit particles, wherein a mixture of said second grit particles to said first grit particles comprises from about 75-98% of said mixture of particles wherein said plurality of second grit particles are configured in a single layer or multiple layers wherein said plurality of second grit particles comprise a total combined height of 10 to 60% of that of the first grit particles, and   a matrix material bonded to said top surface; said matrix material envelops said second grit particles and said matrix material bonds to and partially surrounds said first grit particles, wherein said first grit particles extend above said matrix material and said second grit particles relative to said top surface.   
     
     
         2 . The coating according to  claim 1 , wherein said first grit particles comprise a cubic boron nitride material, coated silicon carbide (SiC), or another hard ceramic phase. 
     
     
         3 . The coating according to  claim 1 , wherein said matrix material comprises a matrix formed from at least one of Ni, Co and MCrAlY, wherein M is Ni or Co. 
     
     
         4 . The coating according to  claim 1 , wherein said second grit particles are selected from the group consisting of alumina, silicon nitride, cubic boron nitride. 
     
     
         5 . The coating according to  claim 1 , further comprising:
 an adhesion layer coupled to said top surface, wherein said adhesion layer is configured to adhere said first grit particles to said top surface.   
     
     
         6 . The coating according to  claim 5 , wherein said adhesion layer comprises the same material as said matrix material. 
     
     
         7 . The coating according to  claim 1 , wherein said second grit particles are about one tenth of the nominal size of the first grit particles. 
     
     
         8 . A turbine engine component comprising:
 an airfoil having a tip;   a composite abrasive coating bonded to said tip;   said composite abrasive coating comprising an adhesion layer bonded to said tip;   a layer of first grit particles bonded to said adhesion layer;   a plurality of second grit particles dispersed around said first grit particles, said second grit particles being smaller than said first grit particles, wherein a mixture of said second grit particles to said first grit particles comprises from about 75% to about 98% of the total number of particles; and   said second grit particles enveloped in a matrix material surrounding an unexposed portion of said first grit particles; said matrix material coupled to said adhesion layer.   
     
     
         9 . The turbine engine component according to  claim 8 , wherein said first grit particles are sized from about 0.04 to about 1.00 millimeters. 
     
     
         10 . The turbine engine component according to  claim 8 , wherein said second grit particles are sized from 0.004 to about 0.1 millimeters. 
     
     
         11 . The turbine engine component according to  claim 8 , wherein a diameter of said first grit particles are 10 to 1 the size of a diameter of said second grit particles. 
     
     
         12 . The turbine engine component according to  claim 8 , wherein said matrix material and said second grit particles are configured to distribute a cutting load from individual highly loaded first grit particles to adjacent first grit particles, thereby reducing stress at the matrix material. 
     
     
         13 . The turbine engine system according to  claim 8 , wherein each one of said first grit particles are configured with grit spacing configured to protect said matrix material from wear by an abradable rub. 
     
     
         14 . The turbine engine system according to  claim 8 , further comprising:
 at least one channel formed between said first grit particles, said channels having a width of 1-3 diameters of said first grit particles.   
     
     
         15 . The turbine engine system according to  claim 14 , wherein said channel is located between said first grit particles that are about 40-90 percent recessed below a total height of said first grit particles. 
     
     
         16 . The turbine engine system according to  claim 14 , wherein said channel comprises a composite of said matrix material and said second grit particles. 
     
     
         17 . The turbine engine system according to  claim 14 , wherein said channel comprises a composite having a strength and abrasion resistance greater than a strength and abrasion of said matrix alone, said channel configured to provide support and bonding strength for said first grit particles. 
     
     
         18 . A process for coating a turbine engine airfoil with an abrasive, said process comprising:
 applying an adhesion layer onto a tip of said airfoil;   adhering a plurality of first grit particles to said adhesion layer, wherein spaces are formed between said first grit particles;   filling said spaces between said first grit particles with a plurality of second grit particles, wherein said second grit particles are smaller than the first grit particles, wherein a mixture of said second grit particles to said first grit particles comprises from about 75% to about 98% of said mixture of particles;   enveloping said second grit particles with a matrix material; and   surrounding each of said first grit particles with said matrix material exposing a portion of said first grit particles above said matrix material and said second grit particles.   
     
     
         19 . The process of  claim 18 , further comprising:
 spacing said first grit particles apart, wherein said spacing is configured to protect said matrix material from wear by an abradable rub.   
     
     
         20 . The process of  claim 19 , further comprising:
 distributing a cutting load from individual highly loaded first grit particles to adjacent first grit particles, thereby reducing stress at the matrix composite material.   
     
     
         21 . The process of  claim 19 , wherein said matrix material and said second grit particles combined comprise a strength and abrasion resistance greater than said matrix material alone. 
     
     
         22 . The process of  claim 19 , further comprising applying a base layer to said blade tip prior to applying said adhesion layer.