Greek Ascoloy®, also known as UNS S41800 Stainless, Grade 418 Stainless Steel, or AMS 5616, is a martensitic stainless steel notable for its high temperature strength and creep resistance. It’s composed of 12-14% chromium, 2.5-3.5% tungsten, 1.80-2.20% silicon, 0.15-0.20% carbon, and less than 0.5% manganese and molybdenum. It can be hardened to over 400 HB.
As with other stainless alloys, the high percentages of chromium and nickel give this grade good corrosion resistance, although not as good as the austenitic grades. In the annealed condition, ductility, weldability, and machinability are all fair to good. Its resistance to stress corrosion cracking (SCC) is higher than that of austenitic stainless steel. Because Greek Ascoloy retains its strength at high temperatures and resists SCC, it’s commonly used for compressor blades, vanes, turbine diffuser components, surgical instruments, high-temperature bolts, aircraft landing gear, and components for petrochemical processing plants.
| Property | Value | Notes |
|---|---|---|
| Material Type | Martensitic Stainless Steel | AMS 5616 |
| Composition | Cr ~12-14%, W ~2.5-3.5%, Ni ~1.80-2.20%, Si, Mn, Mo 0.5% max, C ~0.15–0.20%, | Has a BCT structure, lower chromium and nickel than austenitic stainless steels |
| Density | ~7.86 g/cm³ | ~0.036 lb/in³ |
| Maximum Usable Temperature | ~566-649°C | ~1,050-1,200°F |
| Hardness (Brinell) | ~240-311 HB (Annealed) | ~255-477 HB (Hardened) |
| Tensile Strength | ~793-1034 MPa | ~115,000-150,000 psi |
| Yield Strength | ~586-827 MPa | ~85,000-120,000 psi |
| Elongation at Break | ~18-22% | Annealed condition, room temperature |
| Modulus of Elasticity | ~200 GPa | ~2.9 x 107 psi |
| Electrical Conductivity | ~2.8% IACS | |
| Corrosion Resistance | Good | Not as corrosion-resistant as austenitic grades of stainless |
| Machinability | Fair | |
| Weldability | Poor, but possible | Anneal or temper welds for maximum ductility |
| Thermal conductivity | ~25 W/m K | |
| Magnetism | Yes | |
| Applications | Gas turbine components, surgical instruments, valves |
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