Super-duplex wrought products are often welded with near-matching composition welding products, which may require post weld heat treatments for use in aggressive environments. When duplex field welds are exposed to the demanding conditions encountered in geothermal energy production, without a heat treatment, an over-matching nickel-chromium-molybdenum-tungsten welding product is required for optimum corrosion resistance. Welding procedures are known to have a significant effect on the corrosion resistance and mechanical properties of the welded pipe. Thus a study was undertaken to optimize welding procedures and then verify that the resulting welded pipe was fully resistant to the conditions of service. Details of the welding procedures are reported along with the work conducted to evaluate them. This work is then correlated with results from extensive examinations of welded pipes and fittings taken from service. Effects of service exposure on corrosion and mechanical properties of different weld filler metals are shown.

Subject
Weld attack, Test methods, Materials, Piping, Filler metals, Welding, Base metals, Gas tungsten arc welding, Interfaces, Brines, Pitting, Corrosion resistance, Alloys
Keywords:
welding, super-duplex stainless steel, 2507 (S32750), nickel alloy filler metal, ERNiCrMo-14, geothermal, energy, corrosion
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2008
Association for Materials Protection and Performance (AMPP)
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