Highly Corrosion-resistant Ni-base Consumables for Welding and Cladding The main constituent of Nickel-based alloys is Ni as a major element with >50%. Nickel alloys have a higher tolerance for alloying elements in solid solution than stainless steels and other iron-based alloys but maintain good metallurgical stability. These factors have prompted the development of nickel-based alloys with multiple alloying additions to provide resistance to a wide variety of corrosive environments. The most important group of general-purpose nickel alloys are the Inconel® types which are based on the general corrosion and heat resistant alloy 600 made of Ni, Cr and Fe. These alloys are used for applications from cryogenic processes at -196ºC to elevated temperatures of up to 1000ºC. They are also used in power generation for steam turbine power plants, aircraft gas turbines, nuclear power plants, furnaces as

Nickel Alloys Properties / Advantages 

• Austenic Structure 

 • No phase transformations 

 • Do not harden

• In most environments Nickel is more corrosion resistant than Iron  

• Alloying with chromium provides resistance to oxidation thus providing a broad spectrum of alloys for optimum corrosion resistance in both reducing and oxidizing environments

 • High resistance to corrosion fatigue and erosion 

 • Good stress corrosion resistance 

 • High creep strength • Excellent toughness

• Good workability and weldability

Weldability of Nickel Alloys

Nickel alloys can be joined, with some limitations, by all the common types of welding processes such as Manual Metal Arc (MMA / SMAW), Metal Inert Gas (GMAW / MIG), Tungsten Inert Gas (GTAW / TIG), and Submerged Arc Welding (SAW). The welding procedure of Nickel alloys is similar to those of Stainless steel. 

Welding Procedure 

The following hints have to be followed to get sound and highly corrosion resistant weld joints: 

 . • The weld surface can be cleaned by grinding, brushing, or pickling. 

 • The joint area has to be free of contaminations, especially oil, grease, dust, ink, paint, shop dirt, etc. Oxide films have to be removed on both sides of the weld joint to a minimum of 10 mm 

 • The opening angle must be wider than for carbon steel weld preparations, in general, 60-70 degrees 

 • Tack-welding must be performed in shorter intervals and a sufficiently wide root gap of about 2-3 mm has to be provided. When using MMA, electrodes have to be re-baked before welding. The stringer-bead technique is recommended, where weaving should be restricted to 2.5 times the core wire diameter (except for vertical-up- welds). 

 • The electrodes should be held at a steep angle of 10-20 degrees to the vertical and an arc as short as possible should be maintained. End craters have to be filled and ground out on the root run.

 • When welding the other beads, strike the arc approximately 10 mm before the end crater of the last deposited electrode, then move back to the end crater and weld over the strike point. 

 the inter-pass temperature should not exceed 150 °C .  In multiple pass applications, slag and oxide films have to be removed with a stainless steel brush after each pass.

Pre-Heating

Preheating nickel alloys prior to welding is not normally required. However, if the base metal is cold (12°C or less), it should be warmed to at least 20°C above the ambient temperature to prevent I the formation of condensate as moisture can cause weld porosity. Preheat of the steel component may be required when joining a nickel alloy to carbon steel. Preheat is often beneficial when joining special steel castings.