Electrostatic spray for coating aircraft engine components

Abstract

Electrostatic deposition of high performance powdered materials onto gas turbine surfaces. The process also includes post-deposition thermal staging of the deposited powder to provide a durable coating that will satisfy the demands of turbine engine operation. The process envisions application of organic-based powdered materials, glass/ceramic powdered materials and metal-based powdered materials and combinations thereof using electrostatic techniques to components exposed to low temperature operations, such as may be found in the front section of a gas turbine engine or to the exterior portions of an aircraft engine, and metal-containing glass ceramics, glass-ceramic materials, or materials that can be transformed into glass ceramic materials, when applied to components exposed to high temperature operations, such as may be found in the turbine and exhaust sections of a gas turbine engine or the flaps of an aircraft.

1 . A method for coating an aircraft engine component, comprising the steps of: 
 providing a gas turbine engine component;    providing a high performance powder for coating the gas turbine engine component, the powder capable of being electrostatically charged;    providing a high voltage powder spray gun;    establishing a predetermined electrical potential between the powder spray gun and the gas turbine engine component;    charging the high performance powder while simultaneously spraying the powder at a predetermined flow rate onto at least a portion of surface of the gas turbine engine component to achieve a coating of predetermined thickness; and    heat treating the coated component to a temperature sufficient to establish a strong bond between the component surface and the coating.    
   
   
       2 . The method of  claim 2  wherein the step of heat treating the coated component includes heat treating the coated component to a temperature sufficient to establish a strong metallurgical bond between the component surface and the coating.  
   
   
       3 . The method of  claim 1  wherein the step of heat treating includes heat treating the coated component at a temperature of at least about 1500° F.  
   
   
       4 . The method of  claim 1  wherein the step of heat treating includes firing the component to a temperature of 1500° F. in a time of about 6 minutes.  
   
   
       5 . The method of  claim 1  wherein the step of providing a high performance powder includes providing a powder selected from the group consisting of metal powders, organic-based powders, ceramic-based powders and combinations thereof.  
   
   
       6 . The method of  claim 1  wherein the step of providing a high performance powder includes providing a coated metal powder.  
   
   
       7 . The method of  claim 6  wherein the step of providing a high performance powder includes providing MCrAlX powders, the powders coated with a coating, where X is an element selected from the group consisting of gamma prime formers, solid solution strengtheners, grain boundary strengtheners, reactive elements and combinations thereof and M is an element selected from the group consisting of Fe, Co, Ni and combinations thereof.  
   
   
       8 . The method of  claim 7  wherein the MCrAlX powders include powders wherein X includes at least one element selected from the group consisting of Ta, Re Y, Zr, Hf, Si, B, C and combinations thereof.  
   
   
       9 . The method of  claim 7  wherein the high performance powder is NiCrAlY having an oxide coating formed over an outer surface of the powder.  
   
   
       10 . The method of  claim 6  wherein the powders have an average size in the range of about 5-30 microns.  
   
   
       11 . The method of  claim 1  wherein the step of providing a high performance coating in the form of a powder further includes providing a metal powder coated with a coating selected from the group consisting of an inorganic binder and an oxide coating.  
   
   
       12 . The method of  claim 1  further including the step of consolidating the coating prior to the step of heat treating the coating when the coating of predetermined thickness is a dense coating.  
   
   
       13 . The method of  claim 5  wherein the step of providing a high performance powder selected from the group consisting of metal powders, organic-based powders, ceramic-based powders and combinations thereof further includes providing a plurality of powders wherein at least one of the powders selected is a binder.  
   
   
       14 . The method of  claim 13  wherein the binder is a glass frit.  
   
   
       15 . The method of  claim 13  wherein the binder powder is a silicate-based material.  
   
   
       16 . The binder of  claim 13  wherein the binder includes aluminum oxide particles of submicron size and smaller.  
   
   
       17 . The method of  claim 1  wherein the step of providing an aircraft engine component includes providing at least one aircraft engine component selected from the group consisting of a compressor component selected from the group consisting of compressor section components, turbine section components, combustor components and exhaust components.  
   
   
       18 . The method of  claim 1  wherein the aircraft engine components include turbine airfoils, shrouds, flaps, seals, liners, cowls, center bodies and combustors.  
   
   
       19 . The method of  claim 1  wherein the step of providing a high performance powder includes providing iron-based alloy powders.  
   
   
       20 . The method of  claim 19  wherein the iron-based alloy powders additionally include a binder powder.  
   
   
       21 . The method of  claim 1  wherein the method of providing a gas turbine engine component further includes providing a gas turbine engine component wherein a portion of the gas turbine engine component that is to be coated with a high performance coating is coated with a bond coat.  
   
   
       22 . The method of  claim 1  wherein the step of providing a high performance powder includes providing a plurality of layers of powder, each layer having powders of different sizes wherein layers having fine powders provide a higher density than layer having coarse powders.  
   
   
       23 . The method of  claim 1  wherein the step of providing a high performance powder further includes providing a plurality of layers of powder, each layer having a different composition, and each layer having a different composition having different properties.  
   
   
       24 . The method of  claim 23  wherein the different properties include different mechanical properties, different chemical properties, different environmental properties and different physical properties.  
   
   
       25 . The method of  claim 1  wherein the step of providing a high performance powder includes providing a plurality of powders of different composition, and the step of charging while spraying includes charging and spraying the plurality of powders of different compositions at the same time in the same layer.  
   
   
       26 . The method of  claim 25  wherein the step of charging and spraying the plurality of powders of different compositions at the same time in the same layer provides a layer having a novel composition.  
   
   
       27 . The method of  claim 25  wherein the step of charging and spraying the plurality of powders of different compositions at the same time in the same layer provides a layer having a plurality of phases.