Sigma Phase Formation Risk Calculator

Assess sigma phase formation risk in duplex and austenitic stainless steels from composition and service temperature exposure time

Input Parameters

Results

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Sigma Phase Risk
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Peak Formation Temp
°C
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Est. Time to Sigma (1%)
hours
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Max Recommended Service T
°C
Note: Sigma phase (FeCr intermetallic) causes severe embrittlement and pitting corrosion loss. ASME limits service temperatures for duplex stainless steels. Solution annealing at 1050-1100°C dissolves sigma phase.

Reference

Sigma Phase Formation: Susceptibility Factor SF = Cr + 3.5×Mo + 2×Si - Ni Formation range: 600-950°C (peak ~800-850°C) Higher Cr, Mo, Si promote sigma; Ni suppresses it Sigma causes severe embrittlement and loss of corrosion resistance Duplex grades (high Cr+Mo) are most susceptible