Yield, tensile, hardness, Charpy, and elevated-temperature data for super duplex stainless steel
Ferralium 255 (UNS S32550, EN 1.4507) supplied solution-annealed per ASTM A479 delivers roughly twice the yield strength of 316L austenitic stainless steel at the same chloride-pitting resistance, and roughly the same yield as standard duplex 22Cr (S32205) but with PREN ≥ 40 (vs ~35 for 22Cr). The 25Cr-5Ni-3Mo-2Cu-0.2N composition with a balanced ferrite-austenite microstructure (35 to 55% ferrite per ASTM E562) produces a yield strength minimum of 550 MPa, a tensile minimum of 760 MPa, and Charpy V-notch energy ≥ 45 J at -46 °C in the qualifying-thickness range. The hardness cap of 32 HRC for NACE MR0175 sour-service compliance is achieved by solution-anneal at 1080 °C with water quench; no precipitation or cold-work hardening is permitted.
| Property | Minimum | Test method |
|---|---|---|
| Yield strength (Rp0.2) | 550 MPa (80 ksi) | ASTM E8 / A370 |
| Tensile strength (Rm) | 760 MPa (110 ksi) | ASTM E8 / A370 |
| Elongation A5 (4D) | 15% | ASTM E8 |
| Reduction of area, min | 40% | ASTM E8 |
| Hardness, max | 32 HRC (NACE MR0175) | ASTM E18, E10 |
| Charpy V-notch at -46 °C, min | 45 J (longitudinal), 30 J (transverse) | ASTM E23 |
| Ferrite content | 35 to 55% | ASTM E562 (point count) |
| Density | 7.81 g/cm³ | ASTM B311 |
| Modulus of elasticity | 200 GPa (29 × 10⁶ psi) | ASTM E111 |
| Poisson's ratio | 0.30 | ASTM E132 |
| Temperature | Yield (Rp0.2), typical | Tensile (Rm), typical |
|---|---|---|
| 20 °C | 620 MPa | 820 MPa |
| 100 °C | 540 MPa | 780 MPa |
| 200 °C | 490 MPa | 735 MPa |
| 250 °C | 465 MPa | 720 MPa |
| 300 °C (max for design code) | 440 MPa | 700 MPa |
ASME BPVC Section II-D limits the design temperature for ferritic-austenitic super duplex grades to 316 °C (600 °F) because of the risk of 475 °C embrittlement on long-time exposure above 300 °C. NORSOK M-630 caps service temperature at 250 °C for sustained loads to allow design margin against the same embrittlement mechanism.
| Grade | UNS | Yield, MPa | Tensile, MPa | Hardness, HRC max |
|---|---|---|---|---|
| 304L austenitic | S30403 | 170 | 485 | 92 HRB |
| 316L austenitic | S31603 | 170 | 485 | 92 HRB |
| Duplex 2205 | S31803 / S32205 | 450 | 620 | 32 HRC (NACE) |
| Ferralium 255 | S32550 | 550 | 760 | 32 HRC (NACE) |
| Super duplex 2507 | S32750 | 550 | 795 | 32 HRC (NACE) |
| Zeron 100 | S32760 | 550 | 750 | 32 HRC (NACE) |
