Cast product having alumina barrier layer

Abstract

The present invention provides a cast product that can further enhance the stability of an alumina barrier layer and can exhibit further superior oxidation resistance, carburization resistance, nitriding resistance, corrosion resistance, and the like when used under a high-temperature atmosphere. The cast product according to the present invention is a cast product having an alumina barrier layer including an aluminum oxide on a surface of a matrix, and the aluminum oxide is (Al (1-x) M (x) ) 2 O 3 , where M is at least one of Cr, Ni, Si, and Fe, and x satisfies a relationship 0<x<0.5. Furthermore, the cast product according to the present invention is a cast product having an alumina barrier layer including an aluminum oxide on a surface of a matrix, and at least one of Cr, Ni, Si, and Fe forms a solid solution in the aluminum oxide, and at least one of Cr, Ni, Si, and Fe forming the solid solution with Al is contained so as to satisfy a relationship Al/(Cr+Ni+Si+Fe)≧2.0 in an atomic % ratio.

1 - 12 . (canceled) 
     
     
         13 . A cast product having an alumina barrier layer including an aluminum oxide on a surface of a matrix,
 wherein the aluminum oxide is (Al (1-x) M (x) ) 2 O 3 , where M is at least one of Cr, Ni, Si, and Fe, and x satisfies a relationship 0<x<0.5.   
     
     
         14 . The cast product according to  claim 13 ,
 wherein 80 vol % or more of a crystal structure of the aluminum oxide is a corundum structure.   
     
     
         15 . The cast product according to  claim 13 ,
 wherein at least Cr forms a solid solution in the aluminum oxide, and the Cr forming the solid solution with Al is contained so as to satisfy a relationship Al/Cr≧10 in an atomic % ratio.   
     
     
         16 . The cast product according to  claim 13 ,
 wherein at least one of Ni, Si, and Fe forms a solid solution in the aluminum oxide, and a total atomic % of the at least one of Ni, Si, and Fe forming the solid solution with Al is 10 atm % or less.   
     
     
         17 . The cast product according to  claim 13 ,
 wherein the aluminum oxide has a concentrated-Al layer in which the Al/(Cr+Ni+Si+Fe) on the matrix side is larger than that on the surface side.   
     
     
         18 . The cast product according to  claim 17 ,
 wherein a thickness of the concentrated-Al layer is one fifth or more of a thickness of the alumina barrier layer.   
     
     
         19 . The cast product according to  claim 13 ,
 wherein the alumina barrier layer has a surface roughness (Ra) of 15 μm or less.   
     
     
         20 . The cast product according to  claim 13 ,
 wherein the matrix includes C in an amount of 0.05 to 0.7 mass %, Si in an amount of more than 0 mass % to 2.5 mass % or less, Mn in an amount of more than 0 mass % to 3.0 mass % or less, Cr in an amount of 15.0 to 50.0 mass %, Ni in an amount of 18.0 to 70.0 mass %, Al in an amount of 1.0 to 5.0 mass %, rare earth elements in an amount of 0.005 to 0.4 mass %, and Win an amount of 0.5 to 10.0 mass % and/or Mo in an amount of 0.1 to 5.0 mass %, and the balance includes Fe and inevitable impurities.   
     
     
         21 . The cast product according to  claim 20 ,
 wherein the matrix further includes at least one selected from the group consisting of Ti in an amount of 0.01 to 0.6 mass %, Zr in an amount of 0.01 to 0.6 mass %, and Nb in an amount of 0.1 to 1.8 mass %.   
     
     
         22 . The cast product according to  claim 20 ,
 wherein the matrix further includes B in an amount of more than 0 mass % to 0.1 mass % or less.   
     
     
         23 . A reaction tube made of the cast product according to  claim 13 ,
 wherein the alumina barrier layer is formed on an inner surface of the tube through which hydrocarbon gas as a raw material flows.   
     
     
         24 . A cast product having an alumina barrier layer including an aluminum oxide on a surface of a matrix,
 wherein at least one of Cr, Ni, Si, and Fe forms a solid solution in the aluminum oxide, and the at least one of Cr, Ni, Si, and Fe forming the solid solution with Al is contained so as to satisfy a relationship Al/(Cr+Ni+Si+Fe)≧2.0 in an atomic % ratio.   
     
     
         25 . The cast product according to  claim 24 ,
 wherein 80 vol % or more of a crystal structure of the aluminum oxide is a corundum structure.   
     
     
         26 . The cast product according to  claim 24 ,
 wherein at least Cr forms a solid solution in the aluminum oxide, and the Cr forming the solid solution with Al is contained so as to satisfy a relationship Al/Cr≧10 in an atomic % ratio.   
     
     
         27 . The cast product according to  claim 24 ,
 wherein at least one of Ni, Si, and Fe forms a solid solution in the aluminum oxide, and a total atomic % of the at least one of Ni, Si, and Fe forming the solid solution with Al is 10 atm % or less.   
     
     
         28 . The cast product according to  claim 24 ,
 wherein the aluminum oxide has a concentrated-Al layer in which the Al/(Cr+Ni+Si+Fe) on the matrix side is larger than that on the surface side.   
     
     
         29 . The cast product according to  claim 28 ,
 wherein a thickness of the concentrated-Al layer is one fifth or more of a thickness of the alumina barrier layer.   
     
     
         30 . The cast product according to  claim 24 ,
 wherein the alumina barrier layer has a surface roughness (Ra) of 15 μm or less.   
     
     
         31 . The cast product according to  claim 24 ,
 wherein the matrix includes C in an amount of 0.05 to 0.7 mass %, Si in an amount of more than 0 mass % to 2.5 mass % or less, Mn in an amount of more than 0 mass % to 3.0 mass % or less, Cr in an amount of 15.0 to 50.0 mass %, Ni in an amount of 18.0 to 70.0 mass %, Al in an amount of 1.0 to 5.0 mass %, rare earth elements in an amount of 0.005 to 0.4 mass %, and Win an amount of 0.5 to 10.0 mass % and/or Mo in an amount of 0.1 to 5.0 mass %, and the balance includes Fe and inevitable impurities.   
     
     
         32 . The cast product according to  claim 31 ,
 wherein the matrix further includes at least one selected from the group consisting of Ti in an amount of 0.01 to 0.6 mass %, Zr in an amount of 0.01 to 0.6 mass %, and Nb in an amount of 0.1 to 1.8 mass %.   
     
     
         33 . The cast product according to  claim 31 ,
 wherein the matrix further includes B in an amount of more than 0 mass % to 0.1 mass % or less.   
     
     
         34 . A reaction tube made of the cast product according to  claim 24 ,
 the alumina barrier layer being formed on an inner surface of the tube through which hydrocarbon gas as a raw material flows.