INCONEL alloy 751 (UNS N07751) is a precipitation hardenable nickel-chromium alloy, used mainly for the exhaust valves of internal combustion engines. Its limiting chemical composition is shown in Table 1. The alloy has essentially the same excellent physical, mechanical and corrosion-resistance properties as INCONEL alloy X-750. Some physical constants for INCONEL alloy 751 are shown in Table 2. Its thermal properties correspond closely to those published for INCONEL alloy X-750. In the evaluation of materials for exhaust valve applications, nickel-chromium alloys have performed well in a 1675°F (913°C) lead oxide screening test. INCONEL alloy 751 repeatedly offered good results, with corrosion rates averaging 4.31 g/dm2 /h. Like other nickel-chromium alloys, INCONEL alloy 751 also resists attack by other exhaust stream impurities such as sulfur, bromine and chlorine.
Table 1 - Limiting Chemical Composition, % Nickel (+ Cobalt) ..........................................................70.0 min. Chromium....................................................................14.0-17.0 Iron ..................................................................................5.0-9.0 Titanium...........................................................................2.0-2.6 Aluminum ........................................................................0.9-1.5 Niobium (+ Tantalum) ......................................................0.7-1.2 Manganese ...................................................................1.0 max. Silicon ...........................................................................0.5 max. Sulfur ..........................................................................0.01 max. Copper..........................................................................0.5 max. Carbon........................................................................0.10 max
Physical Properties
The physical properties of Inconel 751™ are given in the following table.
Properties |
Metric |
Imperial |
| Density |
8.22 g/cm³ |
0.297 lb/in³ |
| Melting point |
1413°C |
2575°F |
Mechanical Properties
The mechanical properties of Inconel 751™ are outlined in the following table.
Properties |
Metric |
Imperial |
| Tensile Strength (precipitation hardened, value at room temperature) |
1275 MPa |
184900 psi |
| Yield strength (at strain 200%, precipitation hardened, value at room temperature) |
875 MPa |
127000 psi |
| Elongation at break (precipitation hardened) |
25% |
25% |
Thermal Properties
The thermal properties of Inconel 751™ are displayed in the following table.
Properties |
Metric |
Imperial |
| Thermal expansion co-efficient (at 20-100°C/68-212°F) |
12.6 µm/m°C |
7 µin/in°F |
| Thermal conductivity |
12 W/mK |
83.3 BTU in/hr.ft².°F
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