Influence of weld oxide on stress corrosion cracking of duplex stainless steelG. Hinds L. Wickström A. TurnbullNational Physical Laboratory Teddington Middlesex TW11 0LW United KingdomCorrosion resistant alloys such as duplex stainless steel (DSS) are increasingly the material of choice for oilfield applications as a result of the trend towards more extreme temperatures higher pressures and elevated levels of hydrogen sulphide. However the susceptibility of such materials to localised corrosion and stress corrosion cracking (SCC) is a major concern particularly in the vicinity of welds. A systematic investigation has been carried out into the effect of weld oxide on the SCC susceptibility of 25 Cr DSS by varying the oxygen content in the shielding gas to simulate leaks that can occur during welding in the field. Four-point bend testing of welded specimens under conditions close to the pass/fail boundary in the domain diagram for the material revealed a greater tendency for pitting and cracking as a function of oxygen content in the shielding gas. Pitting was the precursor to cracking in the heat tinted region while surface defects from the grinding process were the primary sites for crack initiation in the parent material. The results of the SCC tests were correlated with analysis of oxide composition and near-surface mechanical properties using X-ray photoelectron spectroscopy (XPS) microhardness mapping and residual stress measurements. Electrochemical measurements on unstressed weld specimens under similar test conditions showed no influence of weld oxide on the pitting potential suggesting that stress is a key factor in pit initiation. The implications for materials selection test programmes are discussed.Keywords: duplex stainless steel weld pitting stress corrosion cracking