Engine component comprising corrosion-protection layer and method for manufacture of engine components

Abstract

An engine valve comprising a chromiferous steel and a protective surface layer ( 5 ) which consists of iron chrome oxide. A method for manufacture of an engine valve with a protective layer includes an engine component of a chromiferous steel which is heated ( 200 ) at a predetermined temperature for a predetermined time so that a layer ( 5 ) of iron chrome oxide is formed on the engine component's surface, and the engine component is then cooled ( 300 ) to room temperature.

1 . An engine component comprised of a chromiferous steel and a corrosion-protection surface layer over the steel, the surface layer consists of iron chrome oxide, wherein the engine component is manufactured according to a method which comprises the steps of:
 providing an engine component comprised of a chromiferous steel;   heating ( 200 ) the engine component in air at a temperature of 150 to 500° C. for a predetermined time so that the surface layer of iron chrome oxide is formed from the chromiferous steel on the surface of the engine component; and   thereafter cooling the engine component to room temperature.   
     
     
         2 . The engine component according to  claim 1 , in which the engine component comprises a steel with a chrome content of at least 8 wt % and up to 88 wt % of iron. 
     
     
         3 . The engine component according to  claim 1 , in which the engine component comprises a steel with a chrome content of 20-22 wt % and an iron content of 58-65 wt %. 
     
     
         4 . The engine component according to  claim 1 , in which the engine component is heated at a temperature of between 250 and 350° C. for 1-3 hours. 
     
     
         5 . The engine component according to  claim 1 , in which the surface layer consists of FeCr2O4 and is of spinel type. 
     
     
         6 . The engine component according to  claim 1 , in which the surface layer has a thickness of 5-20 μm. 
     
     
         7 . The engine component according to  claim 1 , in which the surface layer has a hardness of about 1500 HV0.1. 
     
     
         8 . An engine component according to  claim 1 , wherein the engine component ( 1 ) is an engine valve or a valve guide or a valve seat. 
     
     
         9 . A method for manufacture of an engine component having a corrosion-protection layer, comprising the steps of:
 providing an engine component comprised of a chromiferous steel;   heating the engine component in air at a temperature of 150 to 500° C. for a time so that the corrosion-protection layer of iron chrome oxide is formed from the chromiferous steel on the surface of the engine component;   then cooling ( 300 ) the engine component to room temperature;   
     
     
         10 . The method according to  claim 9 , in which the engine component is heated in air with raised oxygen content. 
     
     
         11 . The method according to  claim 9 , in which the engine component comprises a steel with a chrome content of at least 8 wt % and up to 88 wt % of iron. 
     
     
         12 . The method according to  claim 9 , in which the engine component is heated at a temperature of between 250 and 350° C. for 1-3 hours. 
     
     
         13 . The method according to  claim 9 , in which the engine component comprises a steel with a chrome content of 20-22 wt % and an iron content of 58-65 wt %. 
     
     
         14 . An engine component comprised of a chromiferous steel and a corrosion-protection surface layer over the steel, the surface layer comprises iron chrome oxide, wherein the engine component is manufactured according to a method which comprises the steps of:
 providing an engine component comprised of a chromiferous steel;   heating ( 200 ) the engine component in air at a temperature of 150 to 500° C. for a time so that the surface layer of iron chrome oxide is formed from the chromiferous steel on the surface of the engine component; and   thereafter cooling the engine component to room temperature.