686

The consumables in this subfamily are specifically designed to match the chemical and mechanical properties of alloy 686. The high nickel (Ni) and molybdenum (Mo) content provides excellent resistance under reducing conditions. The substantial chromium (Cr) input ensures resistance to oxidizing environments. Both molybdenum (Mo) and tungsten (W) enhance resistance to localized corrosion, such as pitting. The low carbon (C) content helps minimize grain boundary precipitation, ensuring protection from corrosion in welding heat-affected zones. This alloy is characterized by a tough weld metal, free of Nb, ideal for dissimilar joints in superaustenitic and super duplex stainless steels, or combinations with Ni-based alloys. Additionally, it offers outstanding resistance in applications susceptible to sulfuric or hydrochloric acids, combinations thereof, and to interstitial or pitting corrosion in concentrated and high-temperature acidic chloride solutions. It is primarily used in the chemical and petrochemical sectors, for pollution control, oil and gas extraction and refining, and in marine environments. Its effectiveness extends to dissimilar metal welds, ensuring robust protection against detrimental attacks on the weld metal, especially when joining molybdenum-bearing (Mo) alloys or alloy-clad steels.

The nominal composition (wt. %) of the filler metal of this classification is 57 Ni, 21 Cr, 16 Mo, and 4 W.

Single-phase austenitic Ni-Cr-Mo-W alloy.

Used for welding nickel-chromium-molybdenum alloy to itself, to steel, to other nickel-base alloys, and for cladding steel using the GTAW, GMAW, and SAW processes. It is also suitable to weld overmatching 625, C276, C4, C22, 59 alloys and superduplex and superaustenitic steels.

• EN W.Nr.: 2.4606 (NiCr21Mo16W)
• UNS: N06686, N06022, N06059, N06200, N08367, NO8926, NO8031
• PROPRIETARY: Inconel® Alloy 686 (Special Metals), Incoloy® Alloy 25-6MO, 27-7MO (Special Metals)

Before performing welding or heating operations on nickel-based alloys, it is crucial to ensure that the base metal is perfectly clean. Any traces of oil, grease, paint, lubricants, marking pencils, temperature indicators, threading compounds, or similar materials containing sulfur or lead can cause brittleness and cracking in the base metal or weld metal if present during these processes. Welding on fully austenitic and nickel-based steels must be performed with precision, minimizing heat input, interpass temperature, and dilution with the base metal. It is essential to maintain a maximum heat input of 1.5 kJ/mm and a maximum interpass temperature of 100 °C. Post-weld heat treatment is not required to restore corrosion resistance.