NCF 751 Forgings UNS N07751 · W.-Nr. 2.4694 · Alloy 751

Identification

What is NCF 751, and what is it equivalent to?

Four designation systems cover this alloy. Buyers reach it through the Japanese, American, German or trade name, and all four refer to the same nickel-chromium composition.

Hardening comes from titanium, aluminium and niobium. During ageing these form a coherent γ′ phase that pins dislocations at temperature. Since the strength comes from precipitate rather than from cold work, it survives long holds at temperature, which is what an exhaust valve or a turbine ring needs.

Confirm the exact specification and edition on your purchase order. Where a customer specification calls for a particular melt route or test scope, we work to that document rather than to the generic standard.

Chemistry

Chemical composition of NCF 751

Limiting chemical composition in weight percent. Every heat is analysed and the actual ladle analysis is printed on the mill certificate against the heat number.

The aluminium band is what separates NCF 751 from Inconel X-750: 0.9–1.5 % against roughly 0.4–1.0 %. If a drawing calls for X-750 but the service temperature has crept up, this is usually the first grade to look at.

Melting route

Standard practice for NCF 751 forging stock at Jiangyin Jiangnan Metal is EAF + VOD followed by ESR remelt. That route controls sulfur and non-metallic inclusions and gives sound ingot for open-die work. Vacuum-melted stock (VIM + VAR) is available where an aerospace or rotating-part specification calls for it. State this at enquiry stage, since it changes both price and lead time.

Data

Physical and mechanical properties

Physical constants belong to the alloy. The mechanical values below are typical for age-hardened material, not a guarantee. The binding figures are the ones written on your order and reported on the certificate.

Indicative values only. Achievable properties depend on section size, specimen orientation and the agreed heat-treatment cycle. A tangential specimen taken from the bore of a heavy ring will not read the same as a longitudinal specimen from a 60 mm bar. Send us the property table you have to meet and we will confirm it before accepting the order.

Corrosion and oxidation behaviour

In the lead-oxide screening test at 913 °C (1675 °F) used to rank candidate exhaust-valve materials, Alloy 751 averaged a corrosion rate of 4.31 g/dm²/h. Like other nickel-chromium alloys it also resists attack by the sulfur, bromine and chlorine species carried in exhaust streams, and holds useful oxidation resistance to around 980 °C. Relaxation resistance stays good below 540 °C, which is why the alloy appears in high-duty spring applications.

Process

Forging and heat treatment of NCF 751

Two temperature ranges matter here: the band the alloy can be forged in, and the cycle that develops strength afterwards. Both are recorded on the certificate.

Forging

NCF 751 is open-die forged between 980 °C and 1205 °C, reheating to 1205 °C between passes. The alloy stiffens sharply as it drops through the bottom of that band, so passes are planned to keep the workpiece hot and to put enough reduction through the section to break down the as-cast structure. Seamless rolled rings start from an upset and punched pre-form on the ring-rolling mill. The rolling gives circumferential grain flow, which is why a rolled ring performs better in service than a ring cut from plate.

Heat treatment

Parts are supplied solution treated and precipitation aged. The higher aluminium content of NCF 751 allows a shorter ageing cycle than Inconel X-750 while reaching comparable or better strength. The specific solution temperature, ageing steps and hold times are set against your specification and recorded on the EN 10204 3.1 certificate. Those parameters, not the grade name, are what determine the properties you receive. Annealed or as-forged delivery is available if you intend to heat treat after machining.

Supply range

NCF 751 forged product forms we supply

Everything below is made to drawing. There is no stock catalogue for this grade. Each piece is forged from an ingot or billet cut for the order, so a drawing or a dimension set is the first thing we ask for.

Maximum forged weight and maximum ring diameter for this grade depend on the ingot available at the time of enquiry. Send the heaviest and largest item in your package first and we will confirm feasibility before quoting the rest.

Delivery condition options

• As-forged. Black bar or ring, for customers who machine and heat treat in-house.
• Solution treated + aged. The standard condition, tested and certified to the agreed property table.
• Rough machined. Turned and bored with an agreed machining allowance, which cuts your setup time and freight weight.
• Proof machined for UT. Surface prepared so ultrasonic testing can be performed to the required sensitivity.

Where it is used

Applications for NCF 751 forgings

The alloy was designed for one job: the exhaust valve of a high-output internal combustion engine. It has since moved into other parts that have to hold strength through long periods at high temperature.

Quality

Testing, inspection and certification

Everything below can be specified on the order. Anything you do not specify is carried out to our standard practice and reported anyway.

Certification

Every NCF 751 forging ships with an EN 10204 3.1 works certificate carrying the heat number, chemical analysis, heat-treatment record and mechanical test results, signed by our quality department. An EN 10204 3.2 certificate witnessed by a third-party inspection body such as TÜV, SGS, BV, Lloyd’s Register or a nominated inspector of your choice is issued when specified on the order. Marking, heat-number traceability and packing details are agreed before production starts.

Ordering

What to send with an NCF 751 enquiry

A quotation for a made-to-drawing forging needs eight things. Send all eight and you get a firm price instead of a range.

1. Grade and specification. NCF 751, UNS N07751 or Alloy 751, plus the standard you order to: ASTM B637, ASTM B564, JIS G 4901 or your own specification.
2. Drawing or dimensions. A PDF or STEP drawing, or the main dimensions: OD × ID × height for a ring, OD × thickness for a disc, L × Ø for a shaft.
3. Delivery condition. As-forged, solution treated and aged, or rough machined with an allowance.
4. Quantity and schedule. Piece count, whether it repeats, and the date you need material on site.
5. Property requirements. The tensile, yield, elongation and hardness table you have to satisfy, and the test-specimen location.
6. NDT requirements. Ultrasonic standard and acceptance class, plus any PT, MT or PMI.
7. Certification. EN 10204 3.1 or 3.2, and the inspection body if third-party witnessing is required.
8. Marking, packing and delivery terms. Stamping requirements, case or pallet specification, destination port and Incoterm.

Send it to sales@steelforgepieces.com or call +86 189 2135 9659. If you do not have all of it yet, send what you have and we will come back with the missing points.

Manufacturer

Enquiry

Request a quotation for NCF 751 forgings

Related grades

Other nickel alloy forgings from the same works

If NCF 751 does not suit your service conditions, these are the grades most often compared against it.

• Inconel X-751
• Inconel 718
• Inconel 706
• Inconel 625
• Nimonic 80A
• Nimonic 90
• Nimonic 263
• Nimonic 901
• Waspaloy
• Udimet 720
• Rene 41
• Incoloy 901
• Incoloy 925
• Monel K-500
• Hastelloy C-276
• Seamless rolled rings