Nickel Alloy M25S
UNS N24025 · ASTM A494 M25S
M25S (UNS N24025, ASTM A494 M25S) is a silicon-bearing cast nickel-copper alloy in the Monel family, used where hardness and galling resistance matter more than ductility.
Reference datasheet — M25S is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the HT condition
M25S tempers and conditions
M25S is supplied in 3 conditions, soft to hard. HT is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | As-cast condition; softer and slightly less brittle, used where the 300 HB minimum is not contractually required. | 415 | 620 | 2.5 | 25 HRC | 2.4 % IACS |
HTDefault Age hardened | Standard supply condition for wear parts: aged to meet the ASTM A494 minimum 300 HB with maximum galling resistance. | 550 | 760 | 1.5 | 34 HRC | 2.3 % IACS |
Solution treated (~870 °C, quenched) and aged | Full solution treat plus age for the highest and most uniform hardness in heavy or segregated sections. | 590 | 790 | 1 | 35 HRC | 2.2 % IACS |
What is M25S?
M25S (UNS N24025, ASTM A494 M25S) is a silicon-bearing cast nickel-copper alloy in the Monel family, used where hardness and galling resistance matter more than ductility. As cast it reaches about 550 MPa yield, 760 MPa tensile and 320 HB (34 HRC) with service to 450 °C, and is poured as valve trim, pump casings and marine hardware castings for seawater. Elongation is only 1.5 % and machinability is rated 12, so surfaces are usually ground, and the high silicon content makes welding crack-prone; M35-1 is the choice for weldable, ductile Ni-Cu castings. M25S has a density of 8.36 g/cm³ (0.302 lb/in³), heavier than 54% of nickel alloy grades. It melts at 1,010°C (1,850 °F). M25S has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 79% of nickel alloy grades. Elongation at break is 1.5% and the elastic modulus is 172 GPa (24.9 Msi).
What is M25S used for?
- valve trim
- pump casings
- marine hardware castings
Advantages
- Conducts heat well — 18 W/m·K (10.4 BTU/hr·ft·°F), better than 85% of nickel alloy grades
- Low embodied carbon — 11 kg CO₂/kg, better than 85% of nickel alloy grades
- High electrical conductivity — 2.3 % IACS, better than 83% of nickel alloy grades
- High strength — 550 MPa (79.8 ksi), better than 79% of nickel alloy grades
Limitations
- Low fracture toughness — 25 MPa·√m (22.8 ksi·√in), worse than 99% of nickel alloy grades
- Limited formability — 3/100, worse than 97% of nickel alloy grades
- Limited ductility — 1.5%, worse than 96% of nickel alloy grades
- Low stiffness — 172 GPa (24.9 Msi), worse than 90% of nickel alloy grades
- Difficult to weld — 12/100, worse than 90% of nickel alloy grades
M25S properties
Typical room-temperature values for M25S-HT; bars are the position among nickel alloy grades.
Physical3
M25S has a density of 8.36 g/cm³ (0.302 lb/in³), heavier than 54% of nickel alloy grades. It melts at 1,010°C (1,850 °F).
Mechanical16
M25S has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 79% of nickel alloy grades. Elongation at break is 1.5% and the elastic modulus is 172 GPa (24.9 Msi).
Thermal4
M25S is rated for continuous service to 450°C (842 °F). It conducts heat at 18 W/m·K (10.4 BTU/hr·ft·°F), better than 85% of nickel alloy grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical3
M25S conducts electricity at 2.3 % IACS, better than 83% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (75/100), worse than 63% of nickel alloy grades.
Sustainability4
Producing a kilogram of M25S takes about 130 MJ of energy and emits 11 kg of CO₂ — less than 87% of nickel alloy grades. Typical recycled content is 40%.
Manufacturability8
M25S's machinability is not recommended (12/100, worse than 86% of nickel alloy grades); weldability not recommended (12/100); formability not recommended (3/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the nickel alloy family
Yield strength against density for every nickel alloy grade FabDigit runs. M25S is highlighted; hover a dot for its name, or open the interactive family chart.
Working with M25S
Is M25S easy to machine?
Hard and abrasive — use rigid setups, carbide or CBN tooling, low speed with heavy positive feed; finish grinding is often preferred on wear surfaces.
Can M25S be welded?
Poor weldability: high Si promotes hot cracking; limit to minor defect repair with Ni-Cu (ERNiCu-7) filler, preheat and post-weld age, or braze instead.
Can M25S be formed, bent or molded?
Sand or investment casting only; good fluidity from the silicon, but feed heavy sections well as the alloy has low hot ductility.
M25S chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cu | 27 – 33 | 30 |
| Siprovides age hardening and galling resistance | 3.5 – 4.5 | 4 |
| Fe | ≤ 3.5 | 1.5 |
| Mn | ≤ 1.5 | 0.8 |
| C | ≤ 0.25 | 0.15 |
| S | ≤ 0.03 | 0.01 |
| NiNi + Co, remainder | ≥ 60 (balance) |
What surface finishes work on M25S?
Not anodizable; typically supplied ground/lapped or passivated — the alloy is used bare and self-protecting in seawater.
Surface treatments FabDigit runs on nickel alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Nickel Alloy M25S in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- N24025
- ASTM
- A494 M25S
How much does M25S cost?
M25S is a high-cost nickel alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
M25S — frequently asked
What is M25S used for?
M25S is typically used for valve trim, pump casings and marine hardware castings. In short: hardest cast Ni-Cu grade; galling-resistant valve trim alloy; low ductility, grind-finished.
What is the yield strength of M25S?
M25S has a typical yield strength of 550 MPa (79.8 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 79% of nickel alloy grades. Strength varies by condition: see the 3 listed tempers.
Is M25S easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 86% of nickel alloy grades). Hard and abrasive — use rigid setups, carbide or CBN tooling, low speed with heavy positive feed; finish grinding is often preferred on wear surfaces.
Can M25S be welded?
Not readily — weldability is rated not recommended (12/100). Poor weldability: high Si promotes hot cracking; limit to minor defect repair with Ni-Cu (ERNiCu-7) filler, preheat and post-weld age, or braze instead.
What surface finishes work on M25S?
Not anodizable; typically supplied ground/lapped or passivated — the alloy is used bare and self-protecting in seawater.
Can M25S be formed, bent or molded?
Sand or investment casting only; good fluidity from the silicon, but feed heavy sections well as the alloy has low hot ductility.
What is the maximum service temperature of M25S?
M25S is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between M25S-HT and M25S-AC?
HT is the default condition — standard supply condition for wear parts: aged to meet the ASTM A494 minimum 300 HB with maximum galling resistance. AC: as-cast condition; softer and slightly less brittle, used where the 300 HB minimum is not contractually required. Yield strength is 550 MPa in HT versus 415 MPa in AC.
How much does M25S cost?
M25S is a high-cost nickel alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM A494/A494M — Castings, Nickel and Nickel Alloy — ASTM International (2023)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol.15 — Casting — ASM International (2008)
- Monel/Ni-Cu casting alloy data (S-Monel type) — Special Metals / Nickel Institute (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.