Stable high temperature coating

Abstract

A high temperature metallic threaded fastener such as a stainless steel or titanium nut or externally threaded fastener, is coated with a high temperature lubricating coating. The coating is an aqueous solution or suspension of titanium silicate and molybdenum disulfide, and may also include a wetting agent to maintain materials in suspension. Following baking at an elevated temperature the dried lubricating coating includes at least 10% silicon and 20% molybdenum. The coating provides lubrication and avoids seizing or galling despite cycling through very high temperatures well above 500° C. (about 932° F.).

1 . A method comprising: 
 coating a high strength internally threaded nut with a coating of sodium silicate and molybdenum disulfide and a wetting agent in a water suspension;    baking the coated nut at a temperature above 500° F. (about 260° C.) for at least one-half hour, until the coating is dry, and has a composition of at least 10% silicon and at least 20% molybdenum,    mounting the coated nut onto an externally threaded bolt or stud adjacent to a source of high temperatures above 500° C. (about 932° F.);    periodically raising the temperature of the nut to a temperature above 500° C. (about 932° F.);    periodically lowering the temperature to a temperature less than 100° C. about 212° F.); and    removing the nut from the bolt or stud and later replacing it onto the stud or bolt.    
     
     
         2 . A method as defined in  claim 1  wherein said suspension includes at least 5% by weight of molybdenum sulfide and at least 10% by weight of sodium silicate.  
     
     
         3 . A method as defined in  claim 1  wherein the nuts following coating are baked until the resultant dried coating which is formed has a composition of at least 20% silicon and at least 35% molybdenum.  
     
     
         4 . A method as defined in  claim 1  wherein the nuts are baked at a temperature between 600° F. and 1000° F. (about 316° C. to 538° C.).  
     
     
         5 . A method comprising: 
 treating a high strength metal threaded fastener to produce a threaded fastener having a coating including at least 20% silicon and at least 35% molybdenum;    mounting the threaded fastener to a mating threaded fastener adjacent to a source of high temperature above 500° C.;    periodically raising the temperature of the threaded fastener to a temperature above 500° C.;    periodically lowering the temperature to a temperature less than 100° C. (212° F.); and    removing the threaded fastener from the mating threaded fastener and subsequently replacing it.    
     
     
         6 . A method as defined in  claim 5  wherein the coated threaded fastener is a nut.  
     
     
         7 . A method as defined in  claim 5  wherein the coated threaded fastener is an externally threaded fastener.  
     
     
         8 . A method as defined in  claim 5  wherein the fasteners are formulated and baked until the resultant dried coating which is formed has a composition of at least 20% silicon and 35% molybdenum.  
     
     
         9 . A high temperature resistant threaded fastener comprising: 
 a threaded fastener;    a baked coating on said threaded fastener including at least 10% silicon and at least 20% molybdenum.    
     
     
         10 . A threaded fastener as defined in  claim 9  wherein said coating includes at least 20% silicon and at least 35% molybdenum.  
     
     
         11 . A fastener as defined in  claim 9  wherein said fastener is a nut.  
     
     
         12 . A fastener as defined in  claim 9  wherein said fastener is externally threaded.  
     
     
         13 . A fastener as defined in  claim 9  wherein said fastener is formed of stainless steel.  
     
     
         14 . A fastener as defined in  claim 9  wherein said fastener is formed of titanium.  
     
     
         15 . A method comprising: 
 coating a high strength internally threaded metallic unit with a coating of sodium silicate and molybdenum disulfide and a wetting agent in a suspension; and    baking the coating nut until the coating is dry, and has a composition of at least 10% silicon and at least 20% molybdenum.    
     
     
         16 . A method as defined in  claim 15  wherein said internally threaded metallic unit is a nut.  
     
     
         17 . A high temperature resistant lubricated part comprising: 
 a metal part;    a baked coating on said metal part including at least 10% silicon and at least 20% molybdenum.