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Alloy X-750 is a precipitation-hardenable alloy which has been used in applications such as high temperature structural members for gas turbines, jet engine parts, nuclear power plant applications, heat-treating fixtures, forming tools, and extrusion dies. The alloy is highly resistant to chemical corrosion and oxidation and has high stress-rupture strength and low creep rates under high stresses at temperatures up to 1500°F (816°C) after suitable heat treatment.
Element | Min | Max |
---|---|---|
Carbon | -- | 0.08 |
Manganese | -- | 0.30 |
Silicon | -- | 0.50 |
Sulfur | -- | 0.01 |
Nickel + Cobalt | 70.0 min | |
Chromium | 14.0 | 17.0 |
Iron | 5.00 | 9.00 |
Aluminum | 0.40 | 1.00 |
Titanium | 2.25 | 2.70 |
Copper | -- | 0.50 |
Cb + Ta | 0.70 | 1.20 |
Alloy X-750 has excellent resistance to chloride ion stress-corrosion cracking. It exhibits satisfactory resistance to numerous oxidizing environments. The alloy has similar corrosion resistance to alloy 600 in many media.
Density
lb/cu in...................................... 0.300
kg/cu m...................................... 8303
Melting Range
°F........................................ 2540/2600
°C.........................................1393/1427
Temperature | Btu-in/ft²-hr-°F | W/m-K | |
---|---|---|---|
°F | °C | ||
300 600 1000 1200 1400 1600 |
149 316 538 649 760 871 |
117 142 184 199 218 245 |
16.9 20.5 26.5 28.7 31.4 35.3 |
Condition | ohm-cir mil/ft | microhm-mm |
At Room Temperature | ||
Hot Rolled Solution Treated Solution Treated and Aged |
764 716 746 |
1270 1190 1240 |
Temperature | psi x 10(6) | MPa x 10(6) | |
°F | °C | ||
80 500 1000 1350 1500 |
26.7 260.0 538.0 732.0 816.0 |
31.0 28.7 25.0 21.0 18.5 |
213.7 197.9 172.4 144.8 127.6 |
Heat Treatment
Alloy X-750 is austenitic under all conditions. The alloy is heat treated by several different methods depending upon the application or requirement. Two common treatments are:
1. For maximum creep, relaxtion and rupture strength at temperatures above 1100°F (593°C):
Solution Treatment - 2100°F (1149°C), 2 to 4 hrs, air cool.
Intermediate Age - 1550°F (843°C), 24 hrs, air cool.
Final Age -1300°F (704°C), 20 hrs, air cool.
2. For highest room temperature yield strength and tensile ductility:
Stress Equaliztation - 1625°F (885°C), 24 hrs, air cool.
Precipitation Age - 1300°F (704°C), 20 hrs, air cool.
Workability
The furnace temperature should be 2100°F (1149°C)-for optimal starting temperatures of 1950/2000°F. For service below 1100°F (593°C), higher strength can be obtained by combining some cold work with heat treatment because the effects are additive.
Temper |
Tensile Strength, |
Yield Strength |
Elongation |
Hardness, |
Hot-finished + 1300°F/20 hr,A.C |
170,000-206,000 |
120,000-163,000 |
25-15 |
313-400 |
Treatment #1
Solution treatment 2100°F (1149°C), 2 to 4 hrs., air cool intermediate age 1550°F (843°C), 24 hrs., air cool
Final age 1300°F (704°C), 20 hrs., air cool
Test Temperature | Short-Time Tensile Properties Tests | ||||||
---|---|---|---|---|---|---|---|
°F | °C | Yield Strength 0.2% offset | Ultimate Tensile Strength | % Elongation in 2" (50.8 mm) | % Reduction of Area | ||
ksi | MPa | ksi | MPa | ||||
70 1000 1200 1400 1500 |
21.1 538.0 649.0 760.0 816.0 |
92 83 82 68 45 |
634 572 565 469 310 |
161 140 120 80 47 |
1110 965 827 552 324 |
22 20 10 10 20 |
30 30 21 22 32 |