Nimonic 75: Exceptional Excellence in High-Temperature Alloys

┃ Overview

UNS N06075 (Alloy 75, W.Nr. 2.4951, Nimonic® 75) is an 80/20 nickel-chromium alloy featuring controlled additions of titanium and carbon. Renowned for its elevated temperature strength, corrosion resistance, and outstanding mechanical properties, this alloy finds extensive applications across diverse fields. Currently, it is predominantly employed in sheet applications that demand both oxidation and scaling resistance, along with medium strength at elevated operating temperatures. Furthermore, Nimonic 75 is easily fabricated and weldable.

┃ Application

Aerospace Industry: Gas turbine engines, combustion chambers, afterburners, and other hot sections where the material is exposed to high temperatures, oxidative environments, and mechanical stresses

Chemical Processing: Heat exchangers, reactors, and catalyst systems that handle corrosive chemicals and high-temperature environments

Automotive Industry: Exhaust valves, turbocharger components, and other parts subjected to extreme heat and corrosive conditions

Nuclear Industry: Reactor core components, fuel elements, and other critical parts that require reliable performance at elevated temperatures and in corrosive environments

Petrochemical Industry: Valves, fittings, and heat exchangers

┃ Chemical Composition (%)

┃ Mechanical Property

┃Corrosion Resistance

Nimonic 75 is renowned for its exceptional corrosion resistance across diverse environments. Specifically, Alloy 75 demonstrates remarkable oxidation resistance at elevated temperatures. It develops a protective oxide layer on its surface, effectively preventing additional oxidation and material degradation. This characteristic renders it well-suited for high-temperature applications, including gas turbines and aerospace components.

┃Heat Treatment

Nimonic 75, a nickel-chromium alloy, can undergo heat treatment to improve its mechanical properties. It's crucial to highlight that the precise parameters for heat treatment, such as temperatures, durations, and cooling rates, may vary depending on material specifications or specific application needs. As an illustration, bar cooling is typically performed at 1050°C (1920°F) for 30-60 minutes, followed by air cooling.

┃ Heating and Pickling

Nimonic 75 can undergo a process of heating and pickling to eliminate surface oxides and contaminants. Initially, Alloy 75 is heated within the range of 600-800°C (1112-1472°F) in a controlled atmosphere or under vacuum conditions to facilitate the formation of an oxide scale on the surface. Subsequently, the alloy undergoes a pickling treatment post-heating to eliminate the formed oxide scale and any other surface contaminants. The pickling solution typically comprises an acid-based mixture, such as nitric acid and hydrofluoric acid, known for effectively dissolving the oxide layer. The specific composition and concentration of the pickling solution may vary based on desired outcomes and the extent of the oxide scale.

┃ Hot and Cold Forming

Hot Forming: Nimonic 75 exhibits excellent hot workability within the temperature range of 1220-950°C (2230-1740°F).

Cold Forming: The notable ductility and malleability of annealed Nimonic 75 make it suitable for various cold deformation methods. The alloy undergoes rapid strain hardening, resulting in increased strength, enabling substantial reductions without the risk of rupture.

┃Machining

Nimonic 75 is machinable, but it is recognized for having relatively poor machinability compared to certain other alloys. As a high-strength nickel-chromium alloy with exceptional high-temperature properties, it presents challenges during machining. Special considerations must be taken into account, including tool selection, cutting speed, feed rate, coolant and lubrication usage, rigidity and stability of the machining setup, as well as post-machining treatments.

┃Welding

Nimonic 75 is weldable using MMA, TIG, MIG, and submerged-arc processes. It is recommended to be in the annealed condition before welding, although a limited amount of cold work is acceptable. The permissible cold work varies with the component design, and simple bending and rolling operations may not necessitate reannealing before welding. The affected zone in Alloy 75 does not lead to weld decay, and post-weld heat treatment is generally not required. However, if the equipment is intended for service in contact with caustic soda, fluosilicates, or certain mercury salts, a stress-relieving treatment may be desirable.

┃ Product Forms

Ø Bar & Rod

Ø Plate & Sheet

Ø Coil & Strip

Ø Pipe & Tube

Ø Fitting: Flange, Tee, Elbow, Reducer etc.

Ø Forging: Ring, Shaft, Circle, Block etc.

┃ Note

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