Nickel is the element with the highest content in nickel-based alloys (similar to the iron constituent in stainless steel alloys). Nickel alloys have a number of peculiarities, as outlined in the following. Generally speaking, nickel alloys come into play when stainless steels reach their limits in terms of corrosion resistance, creep and scaling resistance, and suitability for high temperatures. Typical alloy classes are nickel-copper, nickel-iron, nickel-iron-chromium and nickel-molybdenum-chromium. Some nickel alloys do not contain any iron.
Nickel alloys are used in many different industries and applications. These include reactors, heat exchangers, condensers and similar in the chemical industry, turbine blades and membrane wall cladding in flue-gas desulphurization systems in energy, aircraft engine components and seawater-resistant marine installations.
As many nickel alloys are extremely susceptible to hot cracking, the welding techniques and procedures must be adapted accordingly. Most of these alloys also tend to behave very sluggishly when welding, leading to an increased risk of weld defects such as lack of fusion or porosity. Specific weld geometries and special process gases are therefore sometimes required.
A standard mix used for gas metal arc welding (GMAW) or metal active gas (MAG) welding of stainless steels (such as 2.5% CO2 in argon) will not resolve these problems as it would cause excessive oxidation and impair the properties of the nickel alloy. A completely inert gas such as pure argon does not solve the problem either, as it leads to a very sluggish and unstable welding process with poor wetting.
We have pioneered a dedicated portfolio of process gases to overcome these challenges in MAG / GMAW welding of nickel alloys. These specially formulated process gases contain a very low but accurate addition of carbon dioxide (CO2). At levels as low as 550 parts per million (ppm), this CO2 is enough to stabilize the welding process but not enough to compromise the material.
In addition to the tightly controlled, precise CO2 content, gases in our nickel alloy range may contain helium (He) to improve wetting and overcome the sluggishness inherent to most nickel alloys. The addition of 2% hydrogen (H2) may help to keep the welding arc directional, which is especially helpful in out-of-position welding work. H2 can also provide cleaner weld surfaces, making it particularly suited to multi-layer welds. Some gases in this portfolio also contain 5% nitrogen (N2) as a metallurgically active component, thus meeting the needs of certain high-temperature alloys.
Our industry-proven process gases for MAG / GMAW welding of nickel alloys have been successfully deployed by customers across countless applications for over 25 years.
The photos below compare bead-on-plate outcomes when GMAW is applied to an Alloy 59 base metal using a completely inert gas (argon) on the left and our CRONIGON® Ni10 special blend* for nickel alloys on the right
* Please contact your local Linde representative to check what gases, mixtures and supply modes are available in your region
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The images above illustrate how CRONIGON® Ni10 (right) improves wetting and melt pool fluidity in a typical GMAW cladding application relative to argon (left). The gases were used to weld a nickel alloy (Alloy 625) on a carbon steel substrate.
Our welding gases portfolio is marked under different local brands worldwide. As an international company, our products comply with local regulations and market requirements. Contact your local Linde representative to check availability in your region.