Uncovering Sigma Phase Embrittlement in Reverse Osmosis Plants

This article discusses the premature failure of a super duplex stainless steel feed/concentrate port in a reverse osmosis (RO) plant, correlating the manufacturing process flaws to microstructural degradation. An effort was made to correlate σ-phase evolution in super duplex stainless steels with selective corrosion attack of microstructural phases. Significant σ-phase precipitation compromised hardness, contributing to selective corrosion. The study identifies σ-phase embrittlement as the primary damage cause and suggests manufacturing and quality control improvements to prevent similar failures.