High temperature alloys
A compositionally graded alloy construction for separating a low oxygen content corrosive environment from a high oxygen content oxidizing environment includes a wall having a wall thickness and a first surface segment for contacting the low oxygen content corrosive environment, and a second surface segment for contacting the high oxygen content oxidizing environment. The alloy comprises, in weight percent: 0 to 5 Al; 5 to 30 Cr; 0 to 20 Co; 0 to 70 Fe; 0 to 2 Nb; 0 to 2 Ta; 0 to 3 Ti; 0 to 1 Si; 0 to 1 V; 0 to 2 Mn; 0 to 5 Cu; 0 to 30 Mo; 0 to 30 W; 0 to 0.1 P; 0 to 1 Zr; 0 to 1 Hf; 0 to 0.1 Y; 0.05 to 0.5 C; 0 to 0.1 N; and balance Ni.
1. A wall construction for separating a low oxygen content corrosive environment from a high oxygen content oxidizing environment, comprising:
the wall having a wall thickness and a first surface segment for contacting the low oxygen content corrosive environment, and a second surface segment for contacting the high oxygen content oxidizing environment;
the wall comprising wall alloy having a total wall alloy composition comprising, in weight percent: 0 to 5 Al; 5 to 30 Cr; 0 to 20 Co; 0 to 70 Fe; 0 to 2 Nb; 0 to 2 Ta; 0 to 3 Ti; 0 to 1 Si; 0 to 1 V; 0 to 2 Mn; 0 to 5 Cu; 0 to 30 Mo; 0 to 30 W; 0 to 0.1 P; 0 to 1 Zr; 0 to 1 Hf; 0 to 0.1 Y; 0.05 to 0.5 C; 0 to 0.1 N; and balance Ni;
the alloy being compositionally graded from the first surface segment having a first surface segment alloy composition to the second surface segment having a second surface segment alloy composition;
the first surface segment alloy composition comprising, in weight percent based on the total weight of the alloy at the first surface segment, 5-15 Cr, 0-70 Fe, 0-5 Co, 0-30 Mo, 0-1 Mn, 0-0.5 Si, 0-0.1 C, and balance Ni;
the second surface segment alloy composition comprising, in weight percent based on the total weight of the alloy at the second surface segment, 15-30 Cr, 0-70 Fe, 0-20 Co, 0-30 Mo, 0-3 Ti, 0-5 Al, 0-0.5 C, and balance Ni;
the wall alloy having a stable FCC austenitic matrix microstructure, with strengthening phases comprising gamma prime with a volume fraction of 1 to 30% and carbides with a volume fraction of 0 to 5%, based on the total volume of the alloy;
the wall providing corrosion resistance to the liquid low oxygen content corrosive environment with O content between 0 to 20,000 ppm and to the high oxygen content oxidizing environment with O partial pressure between 10-20 to 1 bar, such that the depth of corrosion attack on each of the first and second surface segments after 10,000 h at 800° C. is no more than 10% of the wall thickness.
2. The wall construction of claim 1 , wherein the fraction of the strengthening phases is at a maximum over at least 50% of the wall thickness.
3. The wall construction of claim 1 , wherein the wall thickness between the first surface and the second surface is a minimum 2 mm.
4. The wall construction of claim 1 , wherein the wall alloy is deposited by directed energy deposition, with a laser power between 200-2500 W.
5. The wall construction of claim 1 , wherein the wall alloy is deposited by directed energy deposition, with a powder feed rate between 2-20 g/min.
6. The wall construction of claim 1 , wherein the wall alloy is deposited by directed energy deposition, with a scan speed between 5-20 mm/s.
7. The wall construction of claim 1 , wherein the wall alloy is deposited by directed energy deposition, with a hopper disk speed between 0.1 to 5 rpm.
8. The wall construction of claim 1 , wherein the wall alloy is deposited by directed energy deposition, with a layer height between 0.2-2 mm.
9. A functionally graded alloy for separating a low oxygen content corrosive environment from a high oxygen content oxidizing environment, comprising:
a thickness and a first surface segment having a first surface segment alloy composition for contacting the low oxygen content corrosive environment, and a second surface segment having a second surface alloy composition for contacting the high oxygen content oxidizing environment;
the alloy comprising, in weight percent based on the total weight of the alloy: 0 to 5 Al; 5 to 30 Cr; 0 to 20 Co; 0 to 70 Fe; 0 to 2 Nb; 0 to 2 Ta; 0 to 3 Ti; 0 to 1 Si; 0 to 1 V; 0 to 2 Mn; 0 to 5 Cu; 0 to 30 Mo; 0 to 30 W; 0 to 0.1 P; 0 to 1 Zr; 0 to 1 Hf; 0 to 0.1 Y; 0.05 to 0.5 C; 0 to 0.1 N; and balance Ni;
the alloy being compositionally graded from the first surface segment to the second surface segment;
the first surface segment alloy composition comprising, in weight percent based on the total weight of the alloy at the first surface segment 5-15 Cr, 0-70 Fe, 0-5 Co, 0-30 Mo, 0-1 Mn, 0-0.5 Si, 0-0.1 C, balance Ni; and,
the second surface segment alloy composition comprising, in weight percent based on the total weight of the alloy at the second surface segment, 15-30 Cr, 0-70 Fe, 0-20 Co, 0-30 Mo, 0-3 Ti, 0-5 AI, 0-0.5 C, balance Ni.
10. The functionally graded alloy of claim 9 , wherein the alloy has a stable FCC austenitic matrix microstructure, with strengthening phases comprising gamma prime with a volume fraction of 1 to 30% and carbides with a volume fraction of 0 to 5%, based on the total volume of the alloy.
11. A component for a molten salt reactor, the component comprising:
a wall construction for separating a low oxygen content corrosive environment from a high oxygen content oxidizing environment;
the wall having a wall thickness and a first surface segment having a first surface segment alloy composition for contacting the low oxygen content corrosive environment, and a second surface segment having a second surface alloy composition for contacting the high oxygen content oxidizing environment;
the wall comprising wall alloy having a total wall alloy composition comprising, in weight percent: 0 to 5 Al; 5 to 30 Cr; 0 to 20 Co; 0 to 70 Fe; 0 to 2 Nb; 0 to 2 Ta; 0 to 3 Ti; 0 to 1 Si; 0 to 1 V; 0 to 2 Mn; 0 to 5 Cu; 0 to 30 Mo; 0 to 30 W; 0 to 0.1 P; 0 to 1 Zr; 0 to 1 Hf; 0 to 0.1 Y; 0.05 to 0.5 C; 0 to 0.1 N; and balance Ni;
the alloy being compositionally graded from the first surface segment to the second surface segment;
the first surface segment alloy composition comprising, in weight percent based on the total weight of the alloy at the first surface segment, 5-15 Cr, 0-70 Fe, 0-5 Co, 0-30 Mo, 0-1 Mn, 0-0.5 Si, 0-0.1 C, balance Ni;
the second surface segment alloy composition comprising, in weight percent based on the total weight of the alloy at the second surface segment, 15-30 Cr, 0-70 Fe, 0-20 Co, 0-30 Mo, 0-3 Ti, 0-5 AI, 0-0.5 C, balance Ni;
the alloy having a stable FCC austenitic matrix microstructure, with strengthening phases comprising gamma prime with a volume fraction of 1 to 30% and carbides with a volume fraction of 0 to 5%, based on the total volume of the alloy; and,
the wall providing corrosion resistance to the liquid low oxygen content corrosive environment with O content between 0 to 20,000 ppm and to the high oxygen content oxidizing environment with O partial pressure between 10-20 to 1 bar, such that the depth of corrosion attack on each of the first and second surface segments after 10,000 h at 800° C. is no more than 10% of the wall thickness.