High temperature alloys

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.

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.