Alloy 254 SMO is a very high end, molybdenum and nitrogen alloyed super austenitic stainless steel with low carbon content. It demonstrates outstanding resistance to pitting, crevice corrosion stress cracking, and corrosion fatigue uniform corrosion. Alloy 254 SMO is substantially stronger than the common austenitic grades, with strength nearly twice that of 300 series stainless steel. It is also characterized by high ductility and impact strength. With high levels of chromium, molybdenum, and nitrogen, Alloy 254 SMO is frequently used in high chloride environments, such as brackish water, seawater, pulp mill bleach plants, and other chloride process streams. In some applications it has even been found to be a more cost effective substitute for high nickel and titanium alloys.

S31254 F44 1.4547 254SMo two-phase stainless steel overview:
High molybdenum content and high chromium and nitrogen content make the 254SMO have excellent resistance to spot corrosion and crevice corrosion.The addition of copper improves corrosion resistance in some acids.In addition, due to its high nickel content and high chromium and molybdenum content, the 254SMO has good stress corrosion cracking resistance.Numerous field tests and extensive use have shown that, even at slightly higher temperatures, the 254SMO is highly crevices resistant in seawater, and only a few types of stainless steels have this property.The corrosion resistance of the 254SMO in acidic solutions and oxidized halide solutions required for bleaching processes such as paper is comparable to that of the most corrosion-resistant nickel-based and titanium alloys.Due to its high nitrogen content, the mechanical strength of the 254SMO is higher than that of other types of austenitic stainless steels.In addition, the 254SMO has high ductility and impact strength as well as good weldability.The high molybdenum content of the 254SMO allows it to have a higher oxidation rate when annealed, thus having a rougher surface than ordinary stainless steel after pickling.But this has no adverse effect on the corrosion resistance of the steel.

S31254 F44 1.4547 254SMo Chemical composition of stainless steel

Metallographic structure of 254SMO:The 254SMO is a face-centered cubic lattice structure.In order to obtain austenite structure, the 254SMO is normally annealed at temperatures of 1150 to 1200 degrees Celsius.In some cases, the center of the material may have traces of metal mesophase.But in general, they have no adverse impact on impact strength and corrosion resistance.These phases may precipitate at grain boundaries when placed at temperatures between 600 and 1000 degrees Celsius.

APPLICATIONS:

Due to its high levels of molybdenum and nickel, Alloy 254 SMO is frequently used in high chloride environments. Examples of applications that call for the used of Alloy 254 SMO include:

• Petroleum production
• Saltwater handling
• Food and chemical processing equipment
• Pulp mill bleach systems
• Flue gas desulphurization scrubbers
• Tall oil distillation columns
• Offshore oil & gas production equipment
• Desalination equipment

STANDARDS:

• ASTM/ASME: UNS S31254
• EURONORM: FeMi35Cr20Cu4Mo2
• DIN: 2.4660

• ORROSION RESISTANCE

• Excellent resistance to pitting and crevice corrosion due to its high chromium, molybdenum, and nitrogen content
• Has a very low carbon content, which means there is very little risk of carbide precipitation during heating
• Possesses very good resistance in water containing chlorides, therefore, it is suitable for use in seawater as it can be exposed to it for prolonged periods without suffering from crevice corrosio