CORROSION RESISTANCE OF NICKEL ALLOYS AND SUPER AUSTENITIC STAINLESS STEEL WELD CLADDING AS A FUNCTION OF DILUTION

Overlay welding of Nickel alloys is a widely used process for corrosion protection today. It allows generating a compact and tightly bonded layer of corrosion resistant alloy on a framework of less expensive material (like carbon steel). It furthermore gives the possibility of cladding more complicated geometrical forms like e.g. fittings. Overlay welding is therefore increasingly applied in different segments like the Oil&Gas, CPI or Energy Industry.
During the overlay welding process a dilution of the base material with the weld clad will occur. To save costs fabricators try to keep the overlay layer as thin as possible, which can result in a high content of the base material in the clad. The change of the composition of the clad material may change the corrosion resistance.
For the present paper different Nickel alloys as Alloy 625 (UNS N06625), Alloy 59 (UNS N06059), Alloy 825 (UNS N08825) and one Special Stainless Steel (Alloy 31 UNS N08031) are overlay welded in layers of different thicknesses. The dilution is measured by EDX-technique and is also shown as an element concentration diagram in correlation of the layer thickness.
Furthermore results of pitting corrosion in an immersion test with “Green Death” solution will be discussed.