Refractory Metal MHC
MHC (UNS R03680, ASTM B387) is a hafnium-carbide dispersion-strengthened molybdenum alloy supplied as PM hot-worked, stress-relieved, ground or recrystallised bar and plate.
Reference datasheet — MHC 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 SR condition
MHC tempers and conditions
MHC is supplied in 4 conditions, soft to hard. SR is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Recrystallized | Choose for parts that will anyway see service above the recrystallization temperature — stable microstructure and best creep behaviour, but lower RT strength and more notch sensitivity. | 460 | 620 | 8 | 15 HRC | 118 W/m·K |
SRDefault Stress relieved | Standard commercial supply condition for MHC bar, rod and plate: best combination of room-temperature strength, some ductility and dimensional stability. | 800 | 900 | 12 | 25 HRC | 110 W/m·K |
Stress relieved, centerless ground / machined bar | Same metallurgical condition as SR but supplied ground to close tolerance and free of the oxidised/decarburised surface layer — for precision electrodes, pins and die inserts. | 800 | 900 | 12 | 25 HRC | 27 % IACS |
As hot worked / as forged | Pick for maximum as-worked strength in large forged blanks where residual stress and slight distortion during machining are acceptable. | 860 | 960 | 10 | 28 HRC | 27 % IACS |
What is MHC?
MHC (UNS R03680, ASTM B387) is a hafnium-carbide dispersion-strengthened molybdenum alloy supplied as PM hot-worked, stress-relieved, ground or recrystallised bar and plate. The HfC dispersion gives the highest creep and recrystallization resistance among common Mo alloys — 800 MPa yield, 900 MPa tensile, 12% elongation, 25 HRC, 110 W/m·K and service to 1500 °C in vacuum or inert atmosphere. It oxidises rapidly above roughly 600 °C in air, is unsuitable for structural fusion welds and has very low formability (score 15). TZM is the cheaper and more widely stocked alternative when 1500 °C creep strength is not required. MHC has a density of 10.2 g/cm³ (0.368 lb/in³), heavier than 63% of refractory metal grades. It melts at 2,600°C (4,712 °F). MHC has a yield strength of 800 MPa (116 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 90% of refractory metal grades. Elongation at break is 12% and the elastic modulus is 320 GPa (46.4 Msi).
What is MHC used for?
- Rocket engine thrust chambers
- Nuclear reactor components
- Extreme hot-work tooling
- High-temperature fasteners
Advantages
- Low embodied carbon — 9 kg CO₂/kg, better than 93% of refractory metal grades
- High strength — 800 MPa (116 ksi), better than 90% of refractory metal grades
- High service temperature — 1,500°C (2,732 °F), better than 86% of refractory metal grades
- Stiff — 320 GPa (46.4 Msi), better than 84% of refractory metal grades
- High electrical conductivity — 27 % IACS, better than 80% of refractory metal grades
Limitations
- Difficult to weld — 15/100, worse than 93% of refractory metal grades
- Needs corrosion protection — 45/100, worse than 86% of refractory metal grades
- Limited formability — 15/100, worse than 80% of refractory metal grades
MHC properties
Typical room-temperature values for MHC-SR; bars are the position among refractory metal grades.
Physical3
MHC has a density of 10.2 g/cm³ (0.368 lb/in³), heavier than 63% of refractory metal grades. It melts at 2,600°C (4,712 °F).
Mechanical15
MHC has a yield strength of 800 MPa (116 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 90% of refractory metal grades. Elongation at break is 12% and the elastic modulus is 320 GPa (46.4 Msi).
Thermal6
MHC is rated for continuous service to 1,500°C (2,732 °F). It conducts heat at 110 W/m·K (63.6 BTU/hr·ft·°F), better than 79% of refractory metal grades. Thermal expansion is 5.3 µm/m·K (2.94 µin/in·°F).
Electrical3
MHC conducts electricity at 27 % IACS, better than 80% of refractory metal grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 86% of refractory metal grades.
Sustainability4
Producing a kilogram of MHC takes about 135 MJ of energy and emits 9 kg of CO₂ — less than 91% of refractory metal grades. Typical recycled content is 25%.
Manufacturability7
MHC's machinability is poor (30/100, better than 54% of refractory metal grades); weldability poor (15/100); formability poor (15/100).
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 refractory metal family
Yield strength against density for every refractory metal grade FabDigit runs. MHC is highlighted; hover a dot for its name, or open the interactive family chart.
Working with MHC
Is MHC easy to machine?
Machine with sharp positive-rake carbide or CBN tooling, rigid setups, generous coolant and low feeds — the HfC dispersion is abrasive and the alloy is notch sensitive, so avoid sharp internal corners and grind rather than turn for fine finishes.
Can MHC be welded?
Fusion welding (EB/GTAW in high-purity Ar or vacuum) is possible but recrystallizes and embrittles the fusion zone; vacuum brazing or mechanical fastening is preferred for structural joints.
Can MHC be formed, bent or molded?
Formed only warm/hot (typically 300–1200 °C depending on section) because the ductile-brittle transition lies near or above room temperature; parts are usually machined from PM-forged bar or plate.
MHC 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 |
|---|---|---|
| Hfforms fine HfC dispersion | 1 – 1.4 | 1.2 |
| C | 0.05 – 0.12 | 0.1 |
| O | ≤ 0.03 | |
| N | ≤ 0.01 | |
| Fe | ≤ 0.01 | |
| Ni | ≤ 0.01 | |
| Si | ≤ 0.01 | |
| Mo | balance |
What surface finishes work on MHC?
Do not anodize; use chemical/electro-polishing, and for oxidising service apply MoSi₂ (silicide pack) or aluminide/CVD coatings — bare MHC oxidises rapidly above ~600 °C in air.
Equivalent designations
Standards and trade names that resolve to Refractory Metal MHC in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- R03680B387
How much does MHC cost?
MHC is a high-cost refractory metal ($$$$), 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.
MHC — frequently asked
What is MHC used for?
MHC is typically used for rocket engine thrust chambers, nuclear reactor components, extreme hot-work tooling and high-temperature fasteners. In short: highest-creep-strength Mo alloy; stronger than TZM; recrystallization resistant to 1500 °C.
What is the yield strength of MHC?
MHC has a typical yield strength of 800 MPa (116 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 90% of refractory metal grades. Strength varies by condition: see the 4 listed tempers.
Is MHC easy to machine?
Not especially — machinability is rated poor (30/100, better than 54% of refractory metal grades). Machine with sharp positive-rake carbide or CBN tooling, rigid setups, generous coolant and low feeds — the HfC dispersion is abrasive and the alloy is notch sensitive, so avoid sharp internal corners and grind rather than turn for fine finishes.
Can MHC be welded?
Not readily — weldability is rated poor (15/100). Fusion welding (EB/GTAW in high-purity Ar or vacuum) is possible but recrystallizes and embrittles the fusion zone; vacuum brazing or mechanical fastening is preferred for structural joints.
What surface finishes work on MHC?
Do not anodize; use chemical/electro-polishing, and for oxidising service apply MoSi₂ (silicide pack) or aluminide/CVD coatings — bare MHC oxidises rapidly above ~600 °C in air.
Can MHC be formed, bent or molded?
Formed only warm/hot (typically 300–1200 °C depending on section) because the ductile-brittle transition lies near or above room temperature; parts are usually machined from PM-forged bar or plate.
What is the maximum service temperature of MHC?
MHC is rated for continuous use to about 1,500°C (2,732 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between MHC-SR and MHC-RX?
SR is the default condition — standard commercial supply condition for MHC bar, rod and plate: best combination of room-temperature strength, some ductility and dimensional stability. RX: choose for parts that will anyway see service above the recrystallization temperature — stable microstructure and best creep behaviour, but lower RT strength and more notch sensitivity. Yield strength is 800 MPa in SR versus 460 MPa in RX.
How much does MHC cost?
MHC is a high-cost refractory metal ($$$$), 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 B387 — Molybdenum and Molybdenum Alloy Bar, Rod and Wire — ASTM International (2018)
- Molybdenum alloys — MHC, TZM, ML datasheet — Plansee SE (2023)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Refractory Metals) — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials (Molybdenum) — ASM International (2005)
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.