Properties of Nickel: Understanding Welding Materials

Nickel (Ni) is a hard, silvery-white metal with strength, ductility, and corrosion resistance to make it helpful in developing various materials such as wires and aerospace components. Yet, its claim to fame still lies in the humble five-cent coin that bears its name, even though fewer people carry it around today.

Nickel is a relatively good conductor of electricity and heat and is one of only four elements (cobalt, iron, nickel, and gadolinium) easily magnetized at room temperature. And although it is the fifth most abundant element on Earth, it is mainly concentrated below the Earth's crust, making it the second most abundant element (behind iron) in the Earth's inner core.

Interestingly, substantial nickel deposits were discovered in the Sudbury Basin in Canada in 1883, and today about thirty percent of the world's nickel is mined there. Many scientists believe that this particular deposit came from an ancient meteor impact.

Physical Properties of Nickel

By definition, an element’s physical properties refer to its characteristics that can be observed without changing it into another substance. The physical properties of nickel include:

• Color: Silvery-white metal
• Phase: Solid
• Conductivity: Relatively good conductor of heat and electricity
• Ductility: It can be beaten into thin sheets
• Malleability: It can be shaped or bent
• Luster: Exhibits a shine or glow
• Hardness: Harder than iron
• Ferromagnetic: Nickel is easily magnetized
• Melting point: 2,651 degrees Fahrenheit (1,455 degrees Celsius)
• Boiling point: 5,275.4 F (2,913 C)
• Density: 8.912 grams per cubic centimeter

Chemical Properties of Nickel

How does nickel react with other substances? Chemical properties are only observable during a chemical reaction. These reactions are brought about by burning, rusting, heating, exploding, tarnishing, etc. Nickel is a relatively unreactive element. It does not react with air under ambient temperatures, but at higher temperatures, it ignites to form nickel oxide (NiO). And it resists rusting and corrosion.

Mechanical Properties of Nickel

Nickel alloys are easy to work and form without them becoming brittle. As mentioned, they exhibit high strength and corrosion resistance, which remain stable at high temperatures and under cyclic loading, increasing their functioning life and making them much safer.

Nickel alloys combine iron's strength with copper's ductility and workability, allowing it to be hammered into thin sheets. Depending on the conditions, you can expect a nickel alloy component to last 25-35 years, sometimes longer.

Tips for Welding Nickel and Nickel Alloys

Nickel and its alloys can be welded successfully using most welding methods, except for forge welding and oxyacetylene welding. Wrought nickel alloys are welded like austenitic stainless steel, while cast nickel alloys are challenging to weld.

Wrought nickel alloys are typically welded using gas-tungsten arc welding (TIG), gas-metal arc welding (MIG), and shielded metal arc welding (stick welding). No post-weld treatment is required to maintain or restore corrosion resistance, although in some cases, a complete solution anneal will improve corrosion resistance. Heat treatment, such as stress-relieving, may be needed to meet specific requirements.

Minimizing Weld Defects When Welding Nickel and Nickel Alloys

The defects and challenges of welding nickel include:

• Porosity
• High-temperature embrittlement from contaminants
• Weld bead cracking caused by high heat and excessive welding speeds
• Stress-corrosion cracking in service

Porosity: During the MIG and TIG processes, porosity can be avoided by keeping air away from the molten metal. Welders sometimes use gas backing on the underside of the weld. In the GTAW process, using argon with up to 10% H2 as a shielding gas helps prevent porosity. Cracking: Hot cracking of welds can result from contamination by sulfur, lead, phosphorus, cadmium, zinc, tin, silver, boron, bismuth, or any other low-melting-point elements. It can also be caused by high heat input from a high welding current and a low welding speed.

Stress corrosion cracking: Nickel and its alloys do not experience metallurgical changes affecting corrosion resistance. However, when the alloys contact substances such as concentrated caustic soda, fluorosilicates, and some mercury salts, the welds should be stress relieved to avoid stress corrosion cracking. Since resistance to stress-corrosion cracking increases with nickel content, stress-relieving welds in high-nickel-content alloys should not be necessary.

Effect of slag on zinc weldments: Because fabricated nickel alloys are often used in high-temperature service and corrosive environments, all slag should be removed from the finished weldments. If the slag is not removed, corrosion can result. Slag inclusions between the weld beads reduce the weld’s strength, while fluorides in the slag can react with moisture or environmental elements, creating highly corrosive compounds.

Cleanliness is essential when welding nickel!

Workpieces must be completely foreign material-free before they are heated or welded. Removing dirt, oil, and grease by vapor degreasing or cleaning with acetone or any non-toxic solvent is possible. Paint and other materials not soluble in degreasing solvents might require using methylene chloride or alkaline cleaners. If using alkaline cleaners containing sodium carbonate, those cleaners should be removed before welding. Spraying or scrubbing with hot water is suggested, and marking inks are removable using alcohol.

Processing material embedded in the workpiece can be removed by grinding, abrasive blasting, and cleaning with a 10% HCl solution, followed by a thorough water wash. Oxides must also be removed from the welding area because of the difference between the oxide and base metal melting points. Oxides are typically removed by grinding, machining, abrasive blasting, or pickling.

Choose the correct shielding gas

Argon, helium, or a mixture of the two is recommended as a shielding gas for welding nickel and nickel alloys. Adding oxygen, carbon dioxide, or nitrogen to argon gas often cause porosity or erosion of the electrode. Argon with small quantities of hydrogen (typically 5%) can be used and might help avoid porosity in pure nickel while reducing oxide formation during welding.

What is Nickel Used For?

Nickel alloy’s corrosion resistance makes them ideal in marine applications such as piping systems, pump shafts, seawater valves, trolling wire, and strainer baskets. They also work well as shackles for anchor ropes, water and fuel tanks, and many underwater applications, including propeller shafts and keel bolts. Some non-magnetic alloys are used for anchor cable aboard minesweepers and housings on magnetic-field measurement equipment.

Nickel and its alloys are widespread in marine, petroleum, and chemical processing equipment and for the components in desalination plants. Nickel alloys are also found in the air as aircraft turbine components and on the ground in steam turbine power plants.

One of nickel’s primary applications is as an alloying element in stainless steels, alloys steels, non-ferrous metals, and other corrosion-resistant alloys with brand names, including Monel®, Inconel®, Hastelloy®, and Permalloy®.

Nickel coatings can be added to parts and products electrolytically by electroplating, chemically by electroless, or by autocatalytic deposition. And don’t forget all the uses that nickel-plate steel has to offer.

Other applications include:

• Medical applications
• Nuclear power systems components
• Parts for the chemical and petrochemical industries
• Isolators and actuators for communication
• Welding consumables
• Additives in amour plate and burglarproof vaults
• Heating and resistance parts
• Automotive spark plugs
• Power cables

Nickel is also part of rechargeable storage batteries, including nickel-cadmium and nickel-metal hydride-based batteries in mobile phones and stereo equipment.

Recommended Welding Machines for Welding Nickel

Do-it-yourselfers love to create fabrications that are different and challenging. Nickel projects are ideal for the adventurous hobbyist looking beyond the run-of-the-mill welding jobs. However, you’ll want a high-quality welding machine that is budget-friendly and designed for nickel welding.

Talk to the experts at PrimeWeld for the perfect machine for your welding projects, whether ornaments and fixtures or something more practical like rain gutters and tools. They can help you choose the right TIG or MIG welder that meets your needs and budget!

Final thoughts

Nickel is a valuable metal containing several benefits, including strength, ductility, malleability, corrosion resistance, machinability, conductivity, and heat resistance. It is the metal of choice to combine with other metals to make them shinier and more durable.

Because of its many benefits and endless applications, nickel will remain popular across almost every industry!