Acid and alkali resistant Ni—Cr—Mo—Cu alloys with critical contents of chromium and copper
A nickel—chromium—molybdenum—copper alloy resistant to 70% sulfuric acid at 93° C. and 50% sodium hydroxide at 121° C. for acid and alkali neutralization in the field of waste management; the alloy contains, in weight percent, 27 to 33 chromium, 4.9 to 7.8 molybdenum, 3.1 to 6.0 wt. % copper (when chromium is between 30 and 33 wt. %) or 4.7 to 6.0 wt. % copper (when chromium is between 27 and 29.9 wt. %), up to 3.0 iron, 0.3 to 1.0 manganese, 0.1 to 0.5 aluminum, 0.1 to 0.8 silicon, 0.01 to 0.11 carbon, up to 0.13 nitrogen, up to 0.05 magnesium, up to 0.05 rare earth elements, with a balance of nickel and impurities. Titanium or another MC carbide former can be added to enhance thermal stability of the alloy.
1. A nickel-chromium-molybdenum-copper alloy resistant to sulfuric acid, having a corrosion rate of less than 0.45 mm/y in 70% sulfuric acid at 93° C. and resistant to sodium hydroxide, having a maximum internal attack corresponding to corrosion rate of less than 0.45 mm/y in 50% sodium hydroxide at 121° C., consisting essentially of:
27 and 29.9 wt. % chromium
4.9 to 7.8 wt. % molybdenum
4.7 to 6.0 wt. % copper
up to 3.0 wt. % iron
0.3 to 1.0 wt. % manganese
0.1 to 0.5 wt. % aluminum
0.1 to 0.8 wt. % silicon
0.01 to 0.11 wt. % carbon
up to 0.13 wt. % nitrogen
up to 0.05 wt. % magnesium
up to 0.05 wt. % rare earth elements
up to 0.56 wt. % titanium
up to 1.12 wt. % niobium
up to 2.24 wt. % tantalum
up to 2.24 wt. % hafnium
with a balance of nickel and impurities.
2. The nickel-chromium-molybdenum-copper alloy of claim 1 , wherein the alloys are in wrought forms selected from the group consisting of sheets, plates, bars, wires, tubes, pipes, and forgings.
3. The nickel-chromium-molybdenum-copper alloy of claim 1 , wherein the alloy is in cast form.
4. The nickel-chromium-molybdenum-copper alloy of claim 1 , wherein the alloy is in powder metallurgy form.
5. The nickel-chromium-molybdenum-copper alloy of claim 1 , wherein the alloy contains at least one MC carbide former.
6. The nickel-chromium-molybdenum-copper alloy of claim 5 , wherein the MC carbide former is selected from the group consisting of titanium, niobium, tantalum and hafnium.
7. The nickel-chromium-molybdenum-copper alloy of claim 6 , the alloy consisting essentially of 0.20 to 0.56 wt. % titanium.
8. The nickel-chromium-molybdenum-copper alloy of claim 6 , the alloy consisting essentially of 0.30 to 1.12 wt. % niobium.
9. The nickel-chromium-molybdenum-copper alloy of claim 1 , the alloy consisting essentially of 0.60 to 2.24 wt. % tantalum.
10. The nickel-chromium-molybdenum-copper alloy of claim 1 , the alloy consisting essentially of 0.60 to 2.24 wt. % hafnium.
11. The nickel-chromium-molybdenum-copper alloy of claim 1 , wherein the impurities are selected from the group consisting of cobalt, tungsten, sulfur, phosphorous, oxygen and calcium.