What are high nickel alloys?
What is high nickel alloy steel?
Before we explore what high nickel alloy steel is, let's first analyze the properties of nickel in detail.
Nickel has excellent physical and chemical properties that make it an indispensable material in hundreds of thousands of products. The most common use of nickel is alloying - especially with chromium and other metals to make stainless steel and heat-resistant steel.
Properties of Nickel
Nickel has a melting point of up to 1453°C.
It is resistant to corrosion and oxidation.
It is a hard substance, but extremely ductile and tough.
Nickel easily forms alloys, which we will explore in detail below.
It is magnetic at room temperature.
It can be deposited by electroplating (a thin layer of nickel is plated on a metal by electrolytic deposition).
It has catalytic properties (it can speed up chemical reactions).
Nickel is fully recyclable - nickel can be recycled over and over again without loss of quality, contributing to the circular economy (CE) model.
What is nickel alloy steel used for?
High nickel alloy steel is a type of steel with a specific chemical composition that gives it optimal performance in high-temperature, corrosive and oxidizing environments.
Nickel in alloys offers many benefits without affecting the steel's ability to deform.
Typically, these alloys contain varying proportions of nickel to reduce annealing and quenching temperatures, produce greater quench penetration in addition to critical speeds. Finally, these alloys also provide increased strength in components.
Alloy steels include a wide variety of iron-based materials. Nickel content ranges from very low levels (around 0.3% in some alloy steels) to as high as 20% (maraging steels).
The nickel content in each alloy is carefully engineered to provide the perfect combination of strength, hardness, wear resistance, or toughness, far beyond what ordinary carbon steel can offer. They are often used in equipment that provides power, shapes, and cuts metals, or in cryogenic environments where carbon steel's toughness is insufficient.
Nickel alloy steels are key materials for making tools and machinery, enabling industries to make other tools and machinery.
What is the composition of high nickel alloy steel?
High nickel alloys with nickel content between 25% and 65% are most resistant to carbon dioxide and hydrogen sulfide corrosion. There is no specified limit for carbon dioxide corrosion, while hydrogen sulfide corrosion is related to nickel content. Inconel alloys, such as UNS N08825 and UNS N06625, are the most widely used high nickel alloys in the oil industry.
However, there is no precise minimum standard for the composition of high nickel alloy steel. Some sources claim a nickel content of at least 25%, while others consider nickel content above 3% to be high nickel alloy. The composition of high nickel alloy steel depends on the application of the alloy.
In carbon steel and most low alloy steels, when the temperature drops below 24°C, strength and hardness increase, while tensile ductility and toughness decrease. Nickel can improve low temperature toughness. Although still classified as high nickel alloys, steel alloys with nickel content above 3% are sufficient to withstand cold regions.
For example, ferritic steels with nickel contents above 3% are widely used in applications with temperatures ranging from 0°C to -196°C. These applications include liquefied hydrocarbon gas storage tanks, as well as structures and machinery designed for use in cold regions.
These steels take advantage of the effect of the nickel content in lowering the impact transition temperature, thereby improving low temperature toughness. Therefore, steel alloys with nickel contents above 3% are already high for these uses, but may not contain enough nickel for alloys in the petroleum industry.
