Electrospark deposition process for oxidation resistant coating of cooling hole

Abstract

A method of providing an oxidation resistant coating is disclosed. The method includes providing a substrate having a first surface and cooling holes. A portable coating device includes electro-spark deposition (ESD) equipment and an ESD torch connected with the ESD equipment. The ESD torch has an inert gas source and a rotary electrode conductive material. The rotary electrode is positioned within the ESD torch, and is shielded by an inert gas. The rotary electrode applies a compositionally controlled protective coating to the first surface of the substrate. Then the rotary electrode is inserted into the cooling hole and generates an electrospark between rotary ESD electrode and the substrate to form a rounded edge and deposit a coating of electrode material alloy at a cooling hole edge.

What is claimed is: 
     
         1 . A method for providing a coating comprising:
 providing a substrate having a first surface and at least one cooling hole;   providing a portable coating device including:
 electro-spark deposition (ESD) equipment, and 
 an ESD torch electrically connected with the ESD equipment, the ESD torch including: 
 an inert gas source; and 
 a rotary electrode including a conductive material, the rotary electrode disposed within the ESD torch, the rotary electrode shielded by an inert gas, wherein rotary electrode applies a compositionally controlled protective coating to the first surface of the substrate; 
   inserting the rotary electrode at least partially into the cooling hole;   generating an electrospark between rotary ESD electrode and the substrate to form a rounded edge and deposit a coating of electrode material alloy at a cooling hole edge.   
     
     
         2 . The method of  claim 1 , further comprising pressing the rotary electrode into contact with the substrate in the at least one cooling hole. 
     
     
         3 . The method of  claim 1 , wherein the step of inserting the rotary electrode further comprises inserting a tip portion of the rotary electrode into the at least one cooling hole. 
     
     
         4 . The method of  claim 1 , further comprising providing an inert gas curtain around a deposition site at the cooling hole edge by directing a first shielding gas flow at the rotary electrode. 
     
     
         5 . The method of  claim 1 , further comprising providing a second shielding gas flow at the rotary electrode from a bottom surface of the substrate. 
     
     
         6 . The method of  claim 1 , further comprising applying force to the rotary electrode to make contact with the substrate in the at least one cooling hole. 
     
     
         7 . The method of  claim 1 , further comprising forming a metallurgical bond between the substrate and the alloyed coating on an exit edge of the at least one cooling hole. 
     
     
         8 . The method of  claim 3 , further comprising providing a transition portion on the tip portion, the transition portion transitioning from a diameter of the rotary electrode slightly larger than a diameter of the at least one cooling hole to a tip portion having a diameter less than the diameter of the at least one cooling hole to permit partial insertion of tip portion. 
     
     
         9 . The method of  claim 8 , wherein the transition portion comprises a geometry for forming the cooling hole edge. 
     
     
         10 . The method of  claim 9 , wherein the geometry is a rounded edge. 
     
     
         11 . A system for depositing a coating on a cooling hole edge in a substrate, comprising:
 an electrospark device and an electrode removably supported in the electrode holder; the electrospark device configured to apply a coating of a material when inserted into a cooling hole in the substrate and placed into contact with the metal substrate; and   a rotary electrode disposed within the ESD torch, the rotary electrode shielded by an inert gas, wherein the rotary electrode applies a compositionally controlled protective coating to the substrate at an edge of the cooling hole in response to an electrospark generated by an electrical current through the rotary electrode.   
     
     
         12 . The system of  claim 11 , wherein the rotary electrode comprises a partially tapered tip portion, the tip portion configured to be inserted at least partially into the cooling hole. 
     
     
         13 . The system of  claim 12 , wherein the tip portion comprises a transition portion transitioning from a first diameter to a second diameter, the first diameter being equal to a diameter of the rotary electrode larger than a diameter of the cooling hole, and the second diameter of the tip portion being less than the diameter of the cooling hole, wherein the tip portion is at least partially insertable into the cooling hole. 
     
     
         14 . The system of  claim 12 , wherein the tip portion comprises a geometry configured to form a predetermined geometry of an edge of the cooling hole. 
     
     
         15 . The system of  claim 14 , wherein the predetermined geometry comprises a rounded edge. 
     
     
         16 . The system of  claim 11 , wherein the substrate comprises a combustion hardware component. 
     
     
         17 . The system of  claim 16 , wherein the combustion hardware component is a transition piece aft picture frame of a turbine engine, and wherein an edge of the transition piece aft picture frame comprises a plurality of the cooling holes. 
     
     
         18 . The system of  claim 11 , further comprising a first shielding gas flow directed at the tip portion, the first shielding gas flow configured to provide an inert gas curtain around a deposition site at an edge of the cooling hole. 
     
     
         19 . The system of  claim 18 , wherein the protective coating is an oxidation resistant layer over substantially the entire surface of the edge of the cooling hole with a thickness up to 30 mils. 
     
     
         20 . The system of  claim 18 , wherein the electrode alloy comprises, by weight of alloy, from about 20.0 to about 82.0 percent nickel, from about 10.0 to about 28.0 percent chromium, from about 5.0 to about 15.0 percent aluminum, up to 1.5 percent yttrium, and the balance cobalt and incidental impurities. 
     
     
         21 . A turbine engine component of a metal frame substrate including cooling holes, wherein at least one of the cooling holes comprises a rounded edge with a coating adjacent top surface, wherein the rounded edge with the oxidation resistant coating is applied using the method of  claim 1 .