What Is ASTM A494? Cast Nickel Alloy
Key Grades and Wrought Equivalents
| A494 Grade | UNS | Wrought Equivalent | Alloy System |
|---|---|---|---|
| CY-40 | N06040 | Inconel 600 | Ni-Cr |
| CW-6MC | N26625 | Inconel 625 | Ni-Cr-Mo-Nb |
| CW-12MW | N30002 | Hastelloy C-276 | Ni-Mo-Cr |
| CW-2M | N26455 | Hastelloy C-4 | Ni-Mo-Cr |
| CX2MW | N26022 | Hastelloy C-22 | Ni-Cr-Mo-W |
| M-35-1 | N04020 | Monel 400 | Ni-Cu |
| M-30C | N24130 | Monel K-500 | Ni-Cu (age-hardened) |
| CU5MCuC | N08826 | Incoloy 825 | Ni-Fe-Cr-Mo-Cu |
| CN7M | N08007 | Alloy 20 | Ni-Fe-Cr-Mo-Cu |
Mechanical Properties of Common Grades
| Grade | Tensile (min) | Yield (min) | Elongation (min) | Hardness |
|---|---|---|---|---|
| CY-40 (Inconel 600) | 485 MPa (70 ksi) | 205 MPa (30 ksi) | 30% | - |
| CW-6MC (Inconel 625) | 485 MPa (70 ksi) | 275 MPa (40 ksi) | 25% | - |
| CW-12MW (Hast C-276) | 495 MPa (72 ksi) | 275 MPa (40 ksi) | 4% | - |
| M-35-1 (Monel 400) | 450 MPa (65 ksi) | 170 MPa (25 ksi) | 25% | - |
| CN7M (Alloy 20) | 425 MPa (62 ksi) | 170 MPa (25 ksi) | 30% | - |
When to Specify A494 Castings
Standard austenitic stainless steels (CF8M/316) and duplex grades (A995) handle most corrosive services. A494 nickel alloy castings are reserved for environments that exceed stainless steel limits:
- CW-12MW / CX2MW: wet chlorine gas, ferric chloride, hypochlorite, mixed acid environments
- CW-6MC: sour gas (H2S + CO2 + chlorides), subsea production, flue gas desulfurization
- M-35-1: hydrofluoric acid, seawater, reducing acids
- CN7M: sulfuric acid at elevated temperatures, phosphoric acid
- CY-40: high-temperature oxidation, caustic soda
Quality and Testing
ASTM A494 requires solution annealing (specific temperatures vary by grade), chemical analysis, and mechanical testing. Mill test certificates per EN 10204 3.1 document chemistry, heat treatment, and mechanical properties. Supplementary requirements cover radiographic examination, liquid penetrant inspection, and intergranular corrosion testing per ASTM G28. Hydrostatic testing follows the applicable valve standard (ASME B16.34, API 600, or API 6D).
Nickel alloy castings are significantly more expensive than stainless steel. Procurement lead times for A494 valve bodies typically range from 16 to 30 weeks depending on grade, size, and foundry capacity.
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