INCONEL Alloy 751 N07751 For Exhaust Valves Of Internal Combustion Engines
INCONEL alloy 751 (UNS N07751) is a precipitation hardenable nickel-chromium alloy, used mainly for the exhaust valves of internal combustion engines. The alloy has essentially the same excellent physical, mechanical and corrosion-resistance properties as INCONEL alloy X-750. 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.
Chemical composition
| Element | Nickel (+ Cobalt) | Chromium | Iron | Titanium | Aluminum | Niobium (+ Tantalum) | Manganese | Silicon | Sulfur | Copper | Carbon |
| Weight(%) | 70 min | 14.0-17.0 | 5.0-9.0 | 2.0-2.6 | 0.9-1.5 | 0.7-1.2 | 1.0 max | 0.5 max | 0.01 max | 0.5 max | 0.10 max |
INCONEL alloy 751 has excellent hot hardness. As a result, hard facing of valve seat areas for good wear-resistance is unnecessary in most applications.
Tensile Properties
| Temperature |
Yield Strength (0.2% Offset) |
Tensile Strength | Elongation | Reduction of Area | Hardness | |||
| °F | °C | ksi | MPa | ksi | MPa | % | % | HBN |
| Room | Room | 141.5 | 976 | 190.0 | 1310 | 22.5 | 38.2 | 352 |
| 1200 | 649 | 128.9 | 889 | 159.6 | 1100 | 22.5 | 32.1 | 291 |
| 1350 | 732 | 113.5 | 783 | 124.8 | 860 | 18.5 | 25.7 | 235 |
| 1500 | 816 | 76.3 | 526 | 80.3 | 554 | 26.0 | 35.9 | 173 |
Hot working
The hot working range for INCONEL alloy 751 is 1800-2200°F (980-1205°C). The alloy should be reheated to 2200°F (1205°C) whenever its temperature falls below 1800°F (980°C).
Machining
INCONEL alloy 751 is readily machined in the as-hot finished condition. The best procedure is to machine to slightly oversize, precipitation heat treat, then finish to size. A slight permanent contraction (about 0.0003 in/in) takes place during precipitation. Precipitation treated material can
be finish machined to fine finishes and close tolerances, and will have good dimensional stability.
Joining
INCONEL alloy 751 can be joined by the flash butt welding procedures commonly used in valve manufacture. The alloy can also be inertia welded.
Heat treatment
All properties listed in this publication were derived from material direct aged for two hours at 1350°F (732°C). This short-time heat treatment has been found to produce material with the optimum combination of properties consistent with economy. Longer, more complex, aging treatments may be used to improve specific properties required for particular applications. Please consult Special Metals Corporation for further information.
Available forms at A-ONE ALLOY
Round bar, forging, seamless pipe
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