Product having a layer which protects against corrosion, and process for producing a layer which protects against corrosion

Abstract

The invention relates to a product ( 1 ), in particular a gas-turbine blade ( 1 ), having a metallic basic body ( 2 ) to which a protective layer ( 3, 4 ) for protecting against corrosion is bonded. The protective layer ( 3, 4 ) has an inner layer ( 3 ) of a first MCrAlY alloy and an outer layer ( 45 ) having a second MCrAlY alloy, which is bonded to the inner layer ( 3 ). The second MCrAlY alloy is predominantly in the γ-phase. The invention also relates to a process for producing a protective layer ( 3, 4 ) in which the outer layer ( 4 ) is produced by re-melting a region of the inner layer ( 3 ) or by deposition of an MCrAlY alloy from a liquid phase.

What is claimed is:  
     
         1 . A protective layer for protecting a part against corrosion and oxidation at high temperatures, comprising a MCrAlY alloy having alloying constituents essentially consisting of: 
 15% to 35% chromium by weight;    7% to 18% aluminum by weight; and    0% to 20% rhenium by weight, wherein M represents at least one of Fe, Ni and Co, and Y represents at least one of yttrium and at least one equivalent element selected from the group consisting of scandium and rare earths.    
     
     
         2 . The protective layer of  claim 1 , wherein: 
 the chromium content is 15% to 21% by weight,    the aluminum content is 9% to 11.5% by weight,    the rhenium content is 0.5% to 2% by weight, and    a content of the at least one of yttrium and at least one equivalent element selected from the group consisting of scandium and rare earths is 0.05% to 0.7% by weight.    
     
     
         3 . The protective layer of  claim 2 , wherein: 
 the chromium content is 17% by weight,    the aluminum content is 10% by weight,    the rhenium content is 1.5% by weight, and    the content of the at least one of yttrium and at least one equivalent element selected from the group consisting of scandium and rare earths is 0.3% by weight.    
     
     
         4 . The protective layer of  claim 1 , wherein the MCrAlY alloy protective layer comprises: 
 an inner MCrAlY alloy layer which faces the part; and    an outer MCrAlY alloy layer which is predominantly in a γ-phase.    
     
     
         5 . The protective layer of  claim 1 , wherein the part is a component for a gas turbine.  
     
     
         6 . A protective layer for protecting a part against corrosion and oxidation at high temperatures, comprising a MCrAlY alloy having a predominantly γ-phase in an outer portion thereof, wherein M represents at least one of Fe, Ni and Co, and Y represents at least one of yttrium and at least one equivalent element selected from the group consisting of scandium and rare earths.  
     
     
         7 . The protective layer of  claim 6 , wherein the MCrAlY alloy protective layer comprises: 
 an inner MCrAlY alloy layer which faces the part; and    an outer MCrAlY alloy layer, the outer MCrAlY alloy layer being the outer portion of the protective layer having the predominantly γ-phase.    
     
     
         8 . The protective layer of  claim 7 , wherein: 
 the outer MCrAlY alloy layer is a free surface portion of the inner MCrAlY alloy layer, and    the free surface portion is a layer re-melted by at least one of electron beams and ion beams.    
     
     
         9 . The protective layer of  claim 7 , wherein the outer MCrAlY alloy layer is an electrodeposited MCrAlY alloy predominately in the γ-phase.  
     
     
         10 . The protective layer of  claim 6 , wherein the MCrAlY alloy includes zirconium.  
     
     
         11 . The protective layer of  claim 6 , wherein the MCrAlY alloy includes alloying constituents essentially consisting of: 
 15% to 35% chromium by weight,    7% to 18% aluminum by weight, and    0% to 20% rhenium by weight.    
     
     
         12 . The protective layer of  claim 11 , wherein: 
 the chromium content is 15% to 21% by weight,    the aluminum content is 9% to 11.5% by weight,    the rhenium content is 0.5% to 2% by weight, and    a content of the at least one of yttrium and at least one equivalent element selected from the group consisting of scandium and rare earths is 0.05% to 0.7% by weight.    
     
     
         13 . The protective layer of  claim 12 , wherein: 
 the chromium content is 17% by weight,    the aluminum content is 10% by weight,    the rhenium content is 1.5% by weight, and the content of the at least one of yttrium and at least one equivalent element selected from the group consisting of scandium and rare earths is 0.3% by weight.    
     
     
         14 . The protective layer of  claim 6 , wherein the part is a component for a gas turbine.  
     
     
         15 . The protective layer of  claim 6 , wherein the outer portion of the protective layer is almost entirely in the γ-phase.  
     
     
         16 . A protective layer for protecting a component against corrosion and oxidation at high temperatures, essentially consisting of: 
 15% to 21% by weight of chromium;    9% to 11.5% by weight of aluminum;    0% to 2% by weight of rhenium;    0.05% to 0.7% by weight of an element selected from the group consisting of yttrium, scandium and rare earths;    0% to 1% by weight of ruthenium;    a remainder selected from the group consisting of cobalt and nickel; and    production-related impurities.    
     
     
         17 . The protective layer of  claim 16  wherein: 
 The chromium content is 17% by weight,  
 the aluminum content is 10% by weight,  
 the rhenium content is 1.5% by weight, and  
 a content of the element selected from the group consisting of yttrium, scandium and rare earths is 0.3% by weight, it being possible for the contents listed to fluctuate in a manner customary in industrial production.  
 
     
     
         18 . The protective layer of  claim 16 , wherein the protective layer contains so few chromium-rhenium precipitations that there is no significant embrittlement of the protective layer.  
     
     
         19 . The protective layer of  claim 18 , wherein a volume of the chromium-rhenium precipitations is at most 6% by volume.