Nickel Alloy Family — The Complete Guide

Nickel alloys rank among the most extensively utilized materials in the metal industry. Finding widespread applications in diverse fields such as medicine, automotive, and aeronautics just to mention a few.

Read on to know why and every other thing you need to know about nickel alloys including types, properties, applications, and other details.

What are Nickel Alloys?

As you may recall from your high school chemistry, Nickel is a silvery-white metallic element with the atomic number 28 and the symbol Ni. It’s a transition metal with excellent metallic properties — high ductility, top-tier stress resistance just to mention a few.

Moreover, nickels stand as the earth’s fifth most abundant element. It is a surplus in the crust of our planet. Engineers and scientists have extensively developed the material since its discovery, constantly pushing the boundaries of its utility.

Alloying is one such special way of maximizing a material’s mechanical and chemical capabilities. It involves adding different elements to a balanced material to qualitatively improve its inherent properties.

The main component of a nickel alloy is nickel. The other elements which add up to it include elements like copper, iron, chromium, molybdenum, and titanium.

Metallurgists determine the specific properties of nickel alloys by carefully adjusting the quantity and combination of elemental materials mixed with the primary nickel base. This meticulous process enables the utilization of the alloys in a great many situations.

Numerous qualitative improvements will be made to the original material, nickel, based on the exact composition of each alloy.

Another noteworthy aspect is the fact that nickel metal has the ability to alloy with various majority of metals in existence. The exceptional characteristic imparts remarkable versatility to nickel-based alloys.

Consequently, they are highly sought-after as one of the most versatile superalloy families.

General Properties of the Nickel Alloy Family

Below is a glimpse at the most exceptional properties of nickel alloy that make them in high demand across numerous industries. Key general properties of nickel alloys include;

• High ductility and strength
• Excellent stability to heat
• They are superbly resistant to corrosion
• Good ability to conduct heat
• High-temperature capabilities
• Excellent conductor of electricity
• Able to withstand deformation and fatigue
• Highly resistant to wear and abrasion
• They resist stress corrosion and cracking
• Some nickel alloys are biocompatible
• Some have magnetic properties

These properties may vary depending on the various components used in the formation of the alloy. As such, you can easily adapt the finished alloy to various uses.

Types of Nickel Alloys

Given the cast range of applications for nickel, you should not be surprised that there exists a diverse array of nickel alloys.

So as to provide you with a comprehensive understanding of which nickel alloy variants are most suitable for your project, let’s quickly go over the most relevant and commercially prevalent varieties.

The most common types of nickel alloys include;

• Nickel-copper alloys
• Nickel-iron alloys
• Nickel-chromium alloys
• Nickel-titanium alloys 
• Nickel-molybdenum alloys
• Nickel-Chromium-Iron alloys
• Nickel-Chromium-Cobalt alloys
• Nickel-chromium-molybdenum alloys 

Remember that this rundown isn’t comprehensive. There are numerous different kinds of accessible nickel alloys. However, these are just the absolute most prevalent and commercially significant ones.

Chemical composition summary

N.B

The provided composition ranges are approximate and subject to potential variations based on the specific grade or specifications of the particular alloy. Additionally, certain alloys may contain trace amounts of other elements which are not explicitly listed in the table.

Nickel Copper Alloys

NIckel-copper alloys are also called cupronickel alloys. Within the category of nickel alloys, cupronickel alloys form a subset characterized by the essential components of copper and nickel. Nickel copper alloys normally contain about 55% nickel and 10% copper.

The high strength, corrosion resistance, and excellent electrical and thermal conductivity of these alloys feature a one-of-a-kind combination. However, their outstanding resistance to seawater as well as salt water (non-oxidizing alkaline medium) sets them apart from the competition.

Owing to this, shipbuilding companies, offshore oil and gas industries, and other marine applications typically employ cupronickels. If you’re looking to get your hands on these cupro nickels for your project, your best bet is Alloy 400. It’s the topmost commercially important member of the cupro nickels.

Nickel Iron Alloys

As the name suggests, these nickel alloy variants have nickel as the primary base material and iron as the secondary primer. Suppose you’re looking to tackle thermal expansion as a constraint for your project, then you’ll want to consider these guys.

The thermal expansivity of the nickel-iron alloys is low. The implication is; they don’t significantly expand or contract as temperature changes occur. Thusly, they are incredible production materials for precision instruments and by and large for use cases where you must ensure perpetual dimensional stability.

Invar is the flagship nickel-iron alloy. It contains 36% nickel and 64% iron. Other nickel-iron alloys include super invar, containing 32-33% nickel and 67-68% iron, and inovco, containing 50% nickel and 50% iron. 

Members of the nickel-iron subfamily with higher nickel constituents (72-83%) have soft magnetic properties. A greater proportion of nickel equates to more pronounced chemical and mechanical properties.

Nickel-Chromium-Iron alloys

This nickel alloy subgroup takes the strength of the core individual elements — nickel, chromium, and iron — and forges it into a singular product with vastly expanded holistic mechanical and chemical properties.

They are renowned for their outstanding strength, high temperature, and impervious to corrosion and oxidation. Nickel-Chromium-Iron alloys stand as the high-performance materials of choice. By examining the optimal creep rating and rupture rating of these alloys set at high temperatures, you can determine their quality.

Inconel 718 (52.5% nickel, 19% chromium, 18.5% iron, and trace amounts of other substituents) is a prominent member of the most commercially relevant alloys of this subgroup. Other popular alloys include Incoloy® 800 and Nimonic® 80A. 

It is noteworthy that nickel-chromium-iron alloys are occasionally categorized as stainless steel. Nickel, chromium, and iron are the primary constituents of SS. In this category, the nickel-chromium-iron alloys consist of at least 39.5% iron, with nickel and chromium distributed proportionally.

You can typically use nickel-chromium-iron alloys in petrochemical furnaces, shielding materials for heating electric cables, and cracker tubes.

Nickel-chromium-molybdenum alloys 

They are the high-performance alloy variant of the nickel-molybdenum alloy subgroup. Just like the former, the latter has superb corrosion resistance, especially when against strong reducing acids.

Nickel-chromium-molybdenum alloys can also hold out relatively well against oxidizing agents. They’re also highly resistant to crevice and pitting corrosion, which can occur in chloride-containing environments.

If you’re looking to get your hands on some nickel chromium molybdenum high-performance alloy, hastelloy® C-276 is a good place to start. It typically comprises 57% nickel, 16% molybdenum, and 16% chromium. It’s one of the most commercially abundant members of this subgroup.

Other top-placed alloys of the group are the hastelloy® C-22 and Inconel® 625, which also contain molybdenum and chromium.

Mechanical Properties

As you can see, each alloy has different mechanical properties that make them suitable for different applications. Before deciding on a specific nickel alloy subgroup, it is critical to double-check that the target subgroup has the appropriate properties for your project.

Nickel Alloys Vs Stainless Steel

Be mindful that this table only provides a general comparison between stainless steel and nickel alloys. There will be variations in the specific properties of both alloys as a result of the composition and processing of the alloying materials.

Nickel Alloys Vs Titanium

The key differences between titanium and nickel alloys are summarized and listed in the above table. 

Nickel alloys have higher density and melting points than titanium. They also have poorer machinability and thermal conductivity and lower electrical conductivity. 

In the realm of corrosion resistance, nickel alloys often outperform titanium thanks to their inherent characteristics. 

Nickel alloys, being designed as alloys, incorporate supplementary elements that enhance their corrosion resistance properties. This advantageous blend of elements works synergistically to provide superior protection against corrosive environments. 

Unlike nickel alloy(s) that are recognized for their corrosion resistance. Titanium is more widely recognized for its strength and durability, with corrosion resistance that is comparatively less remarkable.

The significance of the alloy composition becomes evident in this case point as it plays a vital role in establishing the overall corrosion resistance capabilities of materials.

Cost-wise, both nickel alloys and titanium have a relatively high price tag, but titanium tends to cost slightly more because of the higher manufacturing costs. 

Ultimately, the choice between nickel alloys and titanium will factor in your specific requirements as both materials have unique properties and advantages.

Manufacturing Process

The modern metallurgy industry is extensive with a history stretching back decades. Metal manufacturers and processing companies typically have their proprietary manufacturing processes. Additionally, the specific end product alloy and its intended application can also influence the manufacturing process.

That said, the overall process for manufacturing nickel alloys is typically universal. The general steps involved in manufacturing nickel alloys are;

Step#1: Melting

The initial step in the manufacturing process involves melting the constituent metals(raw materials). 

Raw materials (nickel, copper, chromium iron, molybdenum, and other elements) sourced from suppliers and qualitatively verified are sent in preset proportions into an electric arc/vacuum induction furnace for melting at high temperatures.

Step#2: Refining

After melting, the next step is to refine the molten alloy to remove impurities. Impurities in significant proportions in the finished product compromise its structural integrity.

Refining removes sulfur, oxygen, and carbon from the molten alloy. Common refining methods include vacuum degassing and electro-slag refining. 

Step#3: Casting

After refining, the now purified alloy molt is cast into ingots or billets. This step involves pouring the molten alloy into a mold and allowing it to solidify. 

The resulting ingots or billets can be further processed into various shapes and forms, such as bars, sheets, or tubes.

Step#4: Hot working

The purpose of hot working is to further shape the nickel alloy. Hot working involves processes such as forging, rolling, or extrusion. 

What happens here is that the casted materials are systematically deformed at high temperatures. This makes it easier to shape the finished product into various forms and sizes.

Step#5: Heat treatment

The nickel alloy undergoes a heat treatment procedure post-hot working to enhance its mechanical properties.

As the name implies, the process of heat treating the production of nickel alloy entails carefully heating the material to a precise temperature and maintaining it at that level for a designated duration. 

This controlled heating and subsequent cooling enhance the alloy’s properties, including strength, hardness, and ductility. By subjecting the nickel alloy to this heat treatment, its overall performance and quality are significantly improved.

Step#6: Machining

Once the nickel alloy has been heat-treated and shaped to the desired form, machining follows. These processes include drilling, milling, or turning to achieve the final dimensions and surface finish.

At the tail end of the manufacturing line, the nickel alloy is inspected and tested to ensure it meets the required specifications and quality standards. Common non-standard tests you’ll find are non-destructive like ultrasonic testing or X-ray inspection and destructive tests such as tensile testing or hardness.

Applications of Nickel Alloys

In metallurgy, nickel alloys are one of the materials that are utilized the most frequently. Their exceptional properties, which make them extremely adaptable to a variety of industries, explain their widespread use. 

With their distinct characteristics, nickel alloys find extensive applications across various sectors, underscoring their indispensability in diverse fields.

Aerospace

The aerospace industry has a high demand for nickel alloys like Alloy 80A.

Thanks to their exceptional creep resistance, they are a core production material for aircraft development. Manufacturers use them to construct jet engine blades, combustion chambers, and exhaust systems.

Chemical processing

Nickel alloys play a pivotal role in chemical processing industries, where they find applications as reactors, heat exchangers, and pipes. 

Their remarkable resistance to corrosion and capacity to withstand high temperatures are among the primary factors driving their utilization in these industries.

The aforementioned properties make nickel alloys a preferred choice for handling aggressive chemical environments and demanding thermal conditions. Alloy C-276 is one of the most reputable materials for chemical processing applications.

Electronics

While nickel alloys may not possess the highest electrical conductivity, they still hold a prominent position in the field of electronics as one of the most extensively utilized materials. 

They are popular because they have a lot of desirable qualities that make them viable for different electronic applications.

These alloys show fantastic protection from corrosion, give strong mechanical strength, and are very stable to extreme temperatures.

Coupled with their availability in diverse forms and compositions, nickel alloys have a lot of applications in electronic components, connectors, and circuitry, contributing to the reliable and efficient functioning of electronic devices. Ni70Cr30 or Nikrothal 70 for instance, are core components of many heating domestic appliances like toasters and heaters.

Medical

The exceptional properties of Nitinols make them highly sought after in the field of medicine for different uses and rightly so.

These shape memory alloys are very biocompatible, ensuring that they are compatible with the human body and reducing the risk of adverse reactions. 

Nitinols are also highly resistant to aggressive disinfection corrosion, making them ideal alternatives in medical implants and equipment that require frequent sterilization.

Furthermore, Nitinols are non-magnetic, meaning they don’t interfere with sensitive electronic equipment. This quality is especially important in medical settings where precise electronic devices are utilized. Dental implants, pacemaker wires, and surgical instruments are only a couple of instances of the different applications where Nitinols are useful.

Automotive

Nickel copper alloys like Monel 400 and the Monel R-450 are utilized in auto parts such as exhaust systems(cylinder liners) and engine components (bearing surfaces, valve heads, pistons, etc). 

Their exceptional capacity to withstand harsh conditions is one of the primary reasons why they are preferred in demanding conditions like high temperatures and corrosive environments.

However, their superiority goes beyond mere durability. These remarkable materials possess another key characteristic: high malleability. Because of this outstanding feature, they are the best option for making components that require intricate shaping, ensuring a precise fit among various engine parts. 

In essence, their impressive malleability complements their heat and their exceptional corrosion resistance, making them an ideal choice for the complex demands of manufacturing intricate engine components.

Final Thoughts

Nickel alloys are very versatile metals that have found numerous applications across various industries due to their exceptional physical, mechanical, and chemical properties. As technology advances, and the reliance on stable materials increases, suffice to say, this tight-knit family of high-performance alloys will continue to be invaluable to the industry.