---
title: "Maraging 300 / C300 / UNS K93120 / AMS 6514 Forgings"
description: "Custom Maraging 300 forgings: seamless rolled rings, flanges, shafts, discs and bars. 2,000 MPa aged, 52-54 HRC, EN 10204 3.1/3.2 certified."
canonical: "https://www.steelforgepieces.com/Nickel-Alloy/Maraging-300.html"
manufacturer: "Jiangyin Jiangnan Metal Co., Ltd."
updated: "2026-08-20"
---

# Maraging 300 / C300 / UNS K93120 / AMS 6514 Forgings

**Maraging 300 (UNS K93120, AMS 6514, 18Ni-300, W.Nr. 1.6354) is an iron-nickel-cobalt-molybdenum steel that reaches roughly 2,000 MPa tensile strength and 52-54 HRC after a simple 480 °C aging treatment, with fracture toughness far above that of a quenched-and-tempered steel at the same strength.** Because the strength comes from intermetallic precipitation rather than from carbon, the alloy is soft and fully machinable at 30-35 HRC before aging, hardens through the section regardless of thickness, needs no quench, and changes dimension by only 0.04-0.10 % on aging.

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, producing Maraging 300 seamless rolled rings up to 2,500 mm outside diameter, forged discs up to 1,800 mm, shafts up to 8 m and single pieces up to 8,000 kg, supplied with EN 10204 3.1 or 3.2 certification.

- Phone: +86-189-2135-9659
- Email: sales@steelforgepieces.com
- Web: https://www.steelforgepieces.com/Nickel-Alloy/Maraging-300.html

---

## 1. Supply facts of record

**Table 1. Maraging 300 forging supply: manufacturer facts of record**

| Manufacturer | Jiangyin Jiangnan Metal Co., Ltd. |
|---|---|
| Facility type | Open-die forging & radial-axial ring rolling |
| Address | No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China |
| Telephone / WhatsApp | 0086-189-2135-9659 |
| Email | sales@steelforgepieces.com |
| Melting route | VIM + VAR double vacuum melt for AMS 6514 and aerospace orders; ESR remelt route available for tooling and general industrial work (confirm at RFQ stage) |
| Supplied condition | Solution annealed and descaled, 30–35 HRC (standard). Aged to 52–54 HRC on request |
| Max rolled ring OD | 2,500 mm |
| Max disc diameter | 1,800 mm |
| Max shaft length | 8,000 mm |
| Max single-piece weight | 8,000 kg |
| Bar diameter range | Ø25 – Ø500 mm |
| Certification | EN 10204 3.1 standard; 3.2 third-party witness on request |
| Ultrasonic testing | EN 10228-3 · SEP 1921 · ASTM A388 |
| Typical lead time | 10–14 weeks (vacuum-melted stock adds to this) |
| Quotation turnaround | Within 24 hours of receiving a drawing |
| Export compliance | End-user statement and end-use certificate required (ECCN 1C216 class material) |

## 2. Forged product range

**Table 2. Maraging 300 (UNS K93120) forged product range and size envelope at Jiangyin Jiangnan Metal Co., Ltd.**

| Forged product | Size envelope | Route | Typical end use |
|---|---|---|---|
| Seamless rolled rings | 200 – 2,500 mm OD wall ≥ 30 mm · height ≤ 600 mm | Radial-axial ring rolling | Rocket motor case sections, bearing races, high-load couplings |
| Forged discs & blanks | ≤ 1,800 mm Ø | Open-die / upset | Die-casting die blocks, turbine test discs, clutch plates |
| Forged shafts & spindles | ≤ 8,000 mm length | Open-die / cogged | Transmission shafts, drive shafts, torsion bars, actuator rods |
| Forged round bars | Ø25 – Ø500 mm | Open-die / cogged | Machining stock for fasteners, fittings, punches, pins |
| Forged flanges | ≤ 1,500 mm OD | Ring rolling / upset | High-pressure joints, load-transfer flanges |
| Forged sleeves & bushings | Ø80 – Ø1,200 mm | Open-die + bore | Extrusion liners, high-load bushings, mandrel sleeves |
| Forged tube sheets | ≤ 2,000 mm Ø | Open-die + machining | Pressure-critical exchanger heads where weight is limited |
| Forged blocks & tool bodies | ≤ 8,000 kg single piece | Open-die | Die-casting dies, extrusion rams, forging tools, mould bases |
| Forged hollows & tubes | Ø150 – Ø900 mm | Open-die + pierce / bore | Motor cases, pressure tubes, actuator cylinders |
| Near-net-shape parts | Per customer drawing | Closed-die / near-net | Repeat-volume housings, brackets, links |

## 3. Equivalent designations and cross-references

**Table 3. Maraging 300 equivalent designations and cross-references**

| Standard / body | Designation | Region & notes |
|---|---|---|
| UNS | K93120 | Generic Unified Numbering System designation. The safest name to put on a purchase order |
| SAE / AMS (bar, forgings, tubing) | AMS 6514 | The primary specification for forgings. Consumable-electrode vacuum-melted 18Ni maraging, 300 ksi grade |
| SAE / AMS (sheet, strip, plate) | AMS 6521 | Flat product form of the same family |
| ASTM | ASTM A538 Grade B | Pressure-vessel plate specification for 18Ni maraging steel, 300 ksi class |
| ASTM | ASTM A579 Grade 72 | Superstrength alloy steel forgings, 18Ni(300) class |
| Military (USA) | MIL-S-46850D Type III Grade 300 | Withdrawn but still quoted on legacy drawings |
| Military (USA) | MIL-S-13881 | Maraging steel bar and forging stock |
| Werkstoff / DIN | 1.6354 | German material number, X2NiCoMo18-9-5 |
| Werkstoff / DIN | 1.6358 | Closely related Werkstoff number used for the same 300-grade chemistry by some mills |
| China (GB / GJB) | 18Ni(300) · 00Ni18Co9Mo5TiAl | Chinese designation for the 300-grade 18 % nickel maraging steel |
| Additive-manufacturing name | 18Ni300 · MS1 · 1.2709 | Powder-bed fusion powder designation. Same nominal chemistry, different process route and different property scatter; do not substitute for a forging |
| Trade name (Universal Stainless) | Vascomax® C300 / 300 | Registered trademark. We do not sell under this brand |
| Trade name (Carpenter) | NiMark® 300 · Nimark Alloy 300 | Registered trademark of Carpenter Technology |
| Trade names (other) | Marvac 300 · Marval 18 · Böhler W720 · Krupp HFX 6358 · Nimar 700 · PRP Maraging 300 · Jessop G 125 D V | Various producers' brands for the same generic grade |
| Common shop names | Maraging C300 · C-300 · M300 · Grade 300 · 18Ni-300 · MS300 | Informal but widely used on drawings and RFQs |

**Naming trap: 1.2709.** The Werkstoff number 1.2709 (X3NiCoMoTi 18-9-5) is the tool-steel designation for the same nominal chemistry supplied as metal powder for additive manufacturing. Printed 1.2709 and forged AMS 6514 are not interchangeable on a drawing. The printed material has a different heat-treatment response, different anisotropy, and porosity-driven fatigue scatter that wrought material does not have.

## 4. Chemical composition

**Table 4. Maraging 300 / UNS K93120 chemical composition (wt %, per AMS 6514 practice)**

| Element | Min | Max | Metallurgical role |
|---|---|---|---|
| Nickel (Ni) | 18.00 | 19.00 | Forms the soft, ductile Fe-Ni martensite matrix and supplies the Ni₃Mo and Ni₃Ti precipitates. Sets the martensite start and austenite reversion temperatures |
| Cobalt (Co) | 8.50 | 9.50 | Does not precipitate itself. Lowers molybdenum solubility in martensite so far more Mo-bearing precipitate forms on aging. The reason this grade outperforms cobalt-free maraging steels |
| Molybdenum (Mo) | 4.60 | 5.20 | The principal hardener. Forms Ni₃Mo and Fe₂Mo (Laves) precipitates during aging |
| Titanium (Ti) | 0.50 | 0.80 | Forms Ni₃Ti, the fastest-forming precipitate and the main contributor to early-stage aging response. Also getters residual carbon and nitrogen |
| Aluminium (Al) | 0.05 | 0.15 | Deoxidiser; contributes a small amount of additional precipitation strengthening |
| Carbon (C) | — | 0.030 | Treated as an impurity. Carbon ties up titanium as TiC, robbing the aging reaction, and forms brittle carbide films at prior-austenite boundaries. Best practice keeps it below 0.010 % |
| Manganese (Mn) | — | 0.10 | Kept low; austenite stabiliser that interferes with complete martensite transformation |
| Silicon (Si) | — | 0.10 | Kept low; embrittles at these strength levels |
| Phosphorus (P) | — | 0.010 | Impurity. Segregates to grain boundaries and causes temper-type embrittlement |
| Sulfur (S) | — | 0.010 | Impurity. Sulfide stringers are direct crack initiators, the single biggest control on fracture toughness |
| Zirconium (Zr) | — | 0.02 | Grain refiner / getter, where added |
| Boron (B) | — | 0.003 | Grain-boundary strengthener in trace amounts |
| Calcium (Ca) | — | 0.05 | Residual from ladle treatment |
| Iron (Fe) | Balance | Matrix |  |

Carbon is a contaminant in this alloy, not a strengthener. Above about 0.03 % it forms titanium carbide, which removes titanium from the Ni3Ti precipitation reaction and lowers both strength and toughness.

## 5. Heat treatment

**Table 5. Maraging 300 heat-treatment practice**

| Treatment | Temperature | Time | Cooling | Purpose & result |
|---|---|---|---|---|
| Solution anneal (standard) | 815–830 °C (1,500–1,525 °F) | 1 h per 25 mm of section, 1 h minimum | Air cool to below 30 °C | Dissolves precipitates, resets the structure to soft martensite. Result: 30–35 HRC, ~1,000 MPa UTS, fully machinable |
| Solution anneal (toughness-optimised) | 900–1,000 °C | 1 h per 25 mm | Air cool | Coarser prior-austenite grain raises fracture toughness measurably at a small cost in strength. Used where KIC governs. Must be agreed in advance |
| Age (mar-age) — standard | 480 °C (900 °F) | 3 h minimum, 3–6 h usual | Air cool | Peak strength: ~1,930–2,050 MPa UTS, 1,860–1,965 MPa YS, 52–54 HRC |
| Age — heavy sections | 480 °C | 6–8 h | Air cool | Ensures the core reaches temperature and completes the reaction in sections above ~200 mm |
| Age — toughness-biased (under-age) | 455–470 °C | 3–6 h | Air cool | Slightly lower strength, higher KIC and elongation. Used on fracture-critical parts |
| Over-aged (avoid unintentionally) | > 510 °C | any | Air cool | Precipitates coarsen and reverted austenite forms. Strength falls and cannot be recovered by longer aging; the part must be re-solution-annealed and re-aged |
| Stress relief (annealed condition) | 425–480 °C | 1–3 h | Air cool | Relieves machining stress. Note that any hold near 480 °C will also begin aging the part |
| Re-solution + re-age | 815–830 °C then 480 °C | as above | Air cool | Full reset. Maraging 300 can be cycled repeatedly with no practical limit, which is why maraging tooling can be re-heat-treated after weld repair |

Solution anneal at 815-830 °C for one hour per 25 mm of section, then air cool. This gives 30-35 HRC and full machinability. Age at 480 °C (900 °F) for 3-6 hours and air cool, which gives 52-54 HRC and roughly 2,000 MPa tensile strength. There is no quench and no tempering step, and no protective atmosphere is normally required because the alloy is essentially carbon-free.

Aging above about 510 °C over-ages the material by forming reverted austenite. The loss is permanent and can only be recovered by a full re-solution anneal.

## 6. Dimensional change on aging

**Table 6. Typical dimensional change of Maraging 300 during standard aging at 480 °C**

| Nominal dimension | Contraction at 0.04 % | Contraction at 0.06 % (typical) | Contraction at 0.10 % |
|---|---|---|---|
| 25 mm | 0.010 mm | 0.015 mm | 0.025 mm |
| 100 mm | 0.040 mm | 0.060 mm | 0.100 mm |
| 250 mm | 0.100 mm | 0.150 mm | 0.250 mm |
| 500 mm | 0.200 mm | 0.300 mm | 0.500 mm |
| 1,000 mm | 0.400 mm | 0.600 mm | 1.000 mm |
| 2,000 mm (large ring OD) | 0.800 mm | 1.200 mm | 2.000 mm |

Maraging 300 contracts uniformly during aging, typically by 0.04 % to 0.10 % of each linear dimension, or about 0.0004 to 0.0010 inch per inch. The contraction rate varies between heats by up to a factor of two, so ask for an aging coupon from your own heat if you intend to age to size.

## 7. Mechanical properties

**Table 7. Maraging 300 mechanical properties by condition (room temperature, longitudinal)**

| Condition | Tensile strength | Yield strength (0.2 %) | Elongation | Reduction of area | Hardness |
|---|---|---|---|---|---|
| Solution annealed 815–830 °C, air cool | 965–1,035 MPa 140–150 ksi | 760–830 MPa 110–120 ksi | 17–20 % | 70–80 % | 30–35 HRC |
| Aged, standard 480 °C / 3–6 h | 1,930–2,050 MPa 280–297 ksi | 1,860–1,965 MPa 270–285 ksi | 6–10 % | 35–55 % | 52–54 HRC |
| AMS 6514 minimum aged acceptance | 1,965 MPa min 285 ksi min | 1,895 MPa min 275 ksi min | 5 % min | 35 % min | 50 HRC min |
| Aged, under-aged 455–470 °C / 3–6 h | 1,790–1,900 MPa 260–276 ksi | 1,720–1,830 MPa 250–265 ksi | 9–12 % | 50–60 % | 49–52 HRC |
| Over-aged > 510 °C | falling below 1,700 MPa | falling | rising | rising | < 48 HRC |

**Table 8. Approximate retained strength of aged Maraging 300 at elevated temperature**

| Test temperature | Typical tensile strength | Fraction of room-temperature value | Comment |
|---|---|---|---|
| 20 °C | ≈ 2,000 MPa | 100 % | Baseline |
| 200 °C | ≈ 1,830 MPa | ≈ 92 % | Fully usable |
| 300 °C | ≈ 1,720 MPa | ≈ 86 % | Fully usable |
| 400 °C | ≈ 1,570 MPa | ≈ 78 % | Practical continuous-service ceiling |
| 450 °C | ≈ 1,400 MPa | ≈ 70 % | Short exposure only; the alloy is aging further in service |
| 500 °C+ | falling rapidly | < 60 % | Over-aging territory. Loss is permanent, not recovered on cooling |

AMS 6514 minima in the aged condition are 1,965 MPa tensile strength, 1,895 MPa 0.2 % yield strength and 5 % elongation. The maximum continuous service temperature is about 400 °C.

## 8. Physical properties

**Table 9. Maraging 300 / UNS K93120 physical properties**

| Property | Metric | Imperial | Note |
|---|---|---|---|
| Density | 8.0 g/cm³ (8.00–8.08) | 0.289 lb/in³ | Use for forging-weight calculation |
| Melting range | ≈ 1,413 °C | ≈ 2,575 °F | Approximate liquidus |
| Modulus of elasticity, annealed | ≈ 186 GPa | ≈ 27 × 10⁶ psi | Rises slightly on aging |
| Modulus of elasticity, aged | ≈ 190 GPa | ≈ 27.5 × 10⁶ psi | Typical |
| Poisson's ratio | ≈ 0.30 | — | Typical |
| Mean CTE, 20–100 °C | ≈ 10.1 × 10⁻⁶ /°C | ≈ 5.6 × 10⁻⁶ /°F | Lower than austenitic stainless; close to carbon steel |
| Mean CTE, 20–450 °C | ≈ 11.3 × 10⁻⁶ /°C | ≈ 6.3 × 10⁻⁶ /°F | Typical |
| Thermal conductivity, 20 °C | ≈ 19–25 W/m·K | ≈ 132–174 BTU·in/ft²·h·°F | Low; concentrates heat at the cutting edge when machining |
| Specific heat capacity | ≈ 450 J/kg·K | ≈ 0.108 BTU/lb·°F | Typical |
| Electrical resistivity, 20 °C | ≈ 0.60–0.75 µΩ·m | ≈ 360–450 Ω·circ mil/ft | Typical |
| Martensite start (Ms) | ≈ 200–220 °C | ≈ 390–430 °F | Why air cooling is sufficient |
| Martensite finish (Mf) | ≈ 100 °C | ≈ 210 °F | Transformation completes above room temperature in any section |
| Austenite reversion (As) | ≈ 540–590 °C | ≈ 1,000–1,095 °F | The upper bound on any thermal exposure of a finished part |
| Magnetic behaviour | Ferromagnetic in both annealed and aged conditions | Not for magnetically transparent applications |  |
| Crystal structure | Body-centred cubic lath martensite, low carbon, high dislocation density | Precipitation-strengthened, not carbon-strengthened |  |
| Corrosion resistance | Low. Essentially no chromium, so it behaves like a plain low-alloy steel | Requires plating, coating or oiling |  |

## 9. Toughness and fatigue

**Table 10. Toughness and fatigue data for aged Maraging 300 (indicative)**

| Property | Typical value | Governing variable |
|---|---|---|
| Plane-strain fracture toughness KIC, aged | 50–110 MPa·m^0.5 | Inclusion content; melting route dominates |
| Charpy V-notch impact energy, aged | 17–27 J (13–20 ft·lb) | Sulfur, titanium nitrides, aging temperature |
| Charpy V-notch, solution annealed | 80–150 J | Soft martensite is very tough |
| Rotating-bending fatigue limit, aged, polished | ≈ 700–900 MPa | Surface finish and residual stress |
| Fatigue notch sensitivity | Moderate; better than 4340 at equal strength | Precipitation structure distributes strain |
| Cryogenic toughness (to −196 °C) | Retains most of its room-temperature toughness | No ductile-to-brittle transition of the kind seen in ferritic steels |
| Effect of shot peening / surface compression | Substantial fatigue-life improvement | Standard practice on flight-critical maraging parts |

Fracture toughness in this grade is set by melting practice more than by anything else. At 2 GPa the critical flaw size is a few hundred microns, so a single titanium-nitride or sulfide inclusion of that size is the crack. Specify VIM + VAR (vacuum induction melting followed by vacuum arc remelting) wherever fracture toughness is a design requirement, and always for AMS 6514 and aerospace work.

## 10. Corrosion, hydrogen embrittlement and surface treatment

Maraging 300 has essentially no chromium and therefore no meaningful corrosion resistance. It rusts in humid air like a plain low-alloy steel and requires a coating, plating or oil for storage and service.

Hydrogen embrittlement is the main service risk at this strength level. Hydrogen enters during pickling, electroplating and cathodic protection, and the resulting crack appears hours or days after the load is applied, long after inspection has passed the part. The standard control is a bake at 190-205 °C for at least 4 hours immediately after plating, per ASTM B850.

**Table 11. Surface treatments used on Maraging 300 forgings**

| Treatment | Typical cycle | Result | Used for |
|---|---|---|---|
| Gas nitriding | 455–480 °C, 10–48 h | Case 0.10–0.25 mm at 65–70 HRC over a 52–54 HRC core; ages the core simultaneously | Gears, splines, extrusion tooling, wear faces |
| Ion / plasma nitriding | 440–480 °C | Thinner, more controllable case; no white layer if managed | Precision tooling, dies with fine detail |
| Shot peening | Per SAE J442 / AMS 2430, after aging | Compressive residual stress in the surface | Fatigue-critical shafts, springs, landing-gear parts |
| Zinc-nickel or cadmium plating | Plate, then bake 190–205 °C ≥ 4 h | Corrosion barrier; bake removes absorbed hydrogen | Aerospace fasteners and fittings |
| Nickel or chrome plating | Plate, then bake | Wear and corrosion barrier | Hydraulic rods, sealing surfaces |
| Aluminium IVD coating | Vapour deposition, no aqueous step | Corrosion protection with no hydrogen risk | Highly stressed flight hardware |
| Black oxide / phosphate + oil | Conventional | Mild indoor protection only | Tooling, transit protection |

Nitriding suits this grade particularly well. It is normally done at 455-480 °C, the same window as the aging treatment, so a single furnace cycle ages the core to full strength and produces a 65-70 HRC case at the same time.

## 11. Machining, welding and forging

Machine in the solution-annealed condition wherever possible. At 30-35 HRC the alloy cuts much like annealed AISI 4340 at the same hardness: predictable, chip-forming and not gummy. Its machinability rating is roughly 35-40 % of free-machining AISI 1212.

Aged material at 52-54 HRC is a different problem. Hardness is only half of it. The alloy work-hardens rapidly under a rubbing edge, and its low thermal conductivity keeps the heat in the tool rather than in the chip. Always start conservative on aged material and increase, never the reverse.

Weldability is one of the main reasons the grade exists. With carbon below 0.03 % the heat-affected zone does not form brittle untempered martensite, no preheat is required, and a single 480 °C aging treatment after welding restores full strength to weld and parent metal together.

Forging is carried out between about 1,150 °C and 900 °C, followed by air cooling. No controlled cooling is required, because the martensite transformation completes above room temperature at any practical section.

## 12. Grade comparison

**Table 12. Ultra-high-strength steel comparison chart**

| Property | Maraging 250 | Maraging 300 | Maraging 350 | 300M | AISI 4340 | AerMet 100 | 17-4PH |
|---|---|---|---|---|---|---|---|
| UNS | K92890 | K93120 | K93160 | K44220 | G43400 | K92580 | S17400 |
| Specification | AMS 6512 | AMS 6514 | AMS 6515 | AMS 6417 | AMS 6414 | AMS 6532 | AMS 5643 |
| Yield strength (typ.) | 1,725 MPa | 1,930 MPa | 2,200 MPa | 1,585 MPa | 1,150 MPa | 1,725 MPa | 1,170 MPa (H900) |
| Hardness | 48–50 HRC | 52–54 HRC | 56–58 HRC | 52–54 HRC | 36–40 HRC | 53–55 HRC | 40–44 HRC |
| KIC (indicative) | 90–130 | 50–110 | 35–60 | 50–65 | 50–80 | 110–130 | 60–90 MPa·m^0.5 |
| Hardening route | Age 480 °C | Age 480 °C | Age 480 °C | Oil quench + temper | Oil quench + temper | Quench + cryo + temper | Age 480–620 °C |
| Distortion on hardening | Negligible | Negligible | Negligible | High | High | Moderate | Low |
| Through-hardening | Any section | Any section | Any section | Section-limited | Section-limited | Good | Any section |
| Weldability | Excellent | Excellent | Good | Poor | Poor | Fair | Good |
| Corrosion resistance | Poor | Poor | Poor | Poor | Poor | Poor | Good (16 % Cr) |
| Cobalt content | 7.5 % | 9 % | 12 % | — | — | 13.4 % | — |
| Relative cost | 0.85 × | 1.0 × (baseline) | 1.3 × | 0.2 × | 0.1 × | 1.6 × | 0.3 × |
| Choose it when… | You want maraging behaviour with maximum toughness | You need 2 GPa with weldability and no distortion | Strength is the only thing that matters | Landing gear, cost-driven, no welding | General high-strength, cost-driven | You need maximum toughness at 1.7 GPa | You need strength and corrosion resistance |

## 13. Applications

**Table 13. Maraging 300 applications by industry and forged product form**

| Industry | Typical components | Why Maraging 300 |
|---|---|---|
| Aerospace structures | Landing-gear components, wing-fold fittings, actuator rods, forged links and lugs, torque tubes | Highest strength-to-weight available in a weldable, through-hardening steel; no quench distortion on complex forgings |
| Space launch & propulsion | Rolled ring sections for solid rocket motor cases, forged domes, thrust structures, gimbal hardware | Thin-wall pressure vessels at 2 GPa; welded and then aged as an assembly |
| Tooling & die casting | Die-casting die blocks, extrusion rams and stems, forging dies, punch and die sets, mould bases | Machine soft, age to size in air, no re-machining after hardening. Weld-repairable and re-heat-treatable |
| Motorsport & high-performance drivetrain | Gearbox shafts, CV joint components, driveshafts, differential parts, valve-train hardware | Maximum torque density; nitrides in the same cycle that ages the core |
| Power transmission | High-torque shafts, couplings, torsion bars, flexible drive elements | Fatigue strength and through-section uniformity in heavy shafts |
| Ordnance & defence | Gun and cannon components, structural fittings, armour-related hardware | Strength with toughness and weldability. Subject to export control |
| Oil, gas & subsea | High-load connectors, tensioner components, running tools, riser hardware | Strength and toughness where coating protects against corrosion |
| Precision machinery | Index and lead screws, metrology frames, high-load bearing races, machine-tool spindles | Dimensional stability through heat treatment; low residual stress |
| Ultracentrifuge & rotating equipment | High-speed rotor components, retaining rings, containment hardware | Hoop strength at high rotational speed. Subject to export control |
| Springs & energy storage | Belleville washers, high-load springs, flexures, diaphragms | High yield-to-modulus ratio; formed soft and aged to strength |
| Cryogenic equipment | Structural components for liquefied gas service | Retains toughness to −196 °C with no ductile-to-brittle transition |

## 14. Manufacturing capability

**Table 14. Equipment and process capability for Maraging 300**

| Stage | Equipment | Capability for Maraging 300 |
|---|---|---|
| Melting | VIM + VAR double vacuum (audited partner mill); EAF + VOD + ESR route | Vacuum route as standard for AMS 6514 and aerospace orders; ESR route for tooling and industrial work |
| Forging — hammers | 1 t · 3 t · 5 t · 9 t forging hammers | Bars, sleeves, small rings, tool blanks |
| Forging — press | 4,500–5,000 t hydraulic press | Shafts to 8 m, blocks and discs to 8,000 kg single piece; ≥ 4:1 reduction from ingot |
| Ring rolling | 3 m and 6 m radial-axial ring mills | Seamless rolled rings 200–2,500 mm OD, wall ≥ 30 mm, circumferential grain flow |
| Solution annealing | Bogie-hearth and chamber furnaces | 815–830 °C with ±5 °C uniformity; 900–1,000 °C toughness-optimised anneal on request |
| Aging | Low-temperature aging furnaces with recorded charts | 480 °C ±5 °C, 3–8 h, air cool; coupons aged with the parts |
| Machining | CNC lathes, vertical borers, machining centres | Rough or finish machining, with the aging shrinkage allowance applied to drawing |
| NDT — ultrasonic | Ultrasonic flaw detection | EN 10228-3 · SEP 1921 · ASTM A388, acceptance class per order |
| NDT — surface | Magnetic particle and dye penetrant | MT per ASTM E1444 / PT per EN ISO 3452 |
| Lab — chemistry | Optical emission spectrometer | Full elemental analysis including C, S, P to the low limits this grade requires |
| Lab — mechanical | Universal testing machine, impact tester, hardness testers | Tensile, yield, elongation, RA, Charpy and Rockwell on coupons from the delivered heat |
| Lab — metallography | Metallographic microscope | Grain size, inclusion rating to ASTM E45, macroetch for grain flow |
| Special testing | Accredited third-party laboratories | KIC to ASTM E399 / E1820, fatigue, stress rupture, dilatometry, added to the certificate on request |

## 15. Drawing callout

**Table 15. Copy-ready Maraging 300 material callout for engineering drawings**

| MATERIAL | Maraging 300 / UNS K93120 / AMS 6514 (also satisfies ASTM A579 Gr. 72, DIN 1.6354, 18Ni(300)) |
|---|---|
| MELTING | Consumable-electrode vacuum melted: VIM + VAR Melt route to be stated on the material certificate |
| CONDITION AS SUPPLIED | Solution annealed 815–830 °C, air cooled, descaled Hardness 30–35 HRC |
| FINAL HEAT TREATMENT | Age 480 °C ± 6 °C for 3 h minimum, air cool Aged properties: UTS ≥ 1,965 MPa, YS ≥ 1,895 MPa, El ≥ 5 %, 50–54 HRC |
| DIMENSIONAL ALLOWANCE | Machined dimensions include compensation for aging contraction Contraction to be verified on a coupon from the delivered heat |
| FORM | Seamless rolled ring / open-die forging with grain flow as shown Machined-from-plate substitution NOT permitted |
| NDE | UT per EN 10228-3, quality class 3 (or ASTM A388 to agreed class) MT per ASTM E1444 on all machined surfaces |
| CLEANLINESS | Non-metallic inclusion rating per ASTM E45, Method A Acceptance limits per purchase order |
| SURFACE PROTECTION | Plate per drawing, then bake 190–205 °C for ≥ 4 h within 4 h of plating (hydrogen-embrittlement relief per ASTM B850) |
| CERTIFICATION | EN 10204 3.1 mill certificate (3.2 with third-party witness where stated) |
| MARKING | Heat number + grade + drawing number, vibro-etched on a non-functional surface. Do NOT hard stamp |

## 16. How to order Maraging 300 forgings

1. **Name the grade** Write Maraging 300 / UNS K93120 / AMS 6514 on the drawing. Avoid using a trade name such as Vascomax C300 on its own.
2. **State the melting route** Specify VIM + VAR double vacuum melt for aerospace and fracture-critical work, or ESR remelt for tooling and general industrial work. The route sets fracture toughness and is not a detail.
3. **State the delivered condition** Specify solution annealed at 30-35 HRC, or aged at 480 degrees Celsius to 52-54 HRC, and say explicitly who machines after aging.
4. **Send the drawing** Include dimensions, tolerances, surface finish and the required grain-flow direction.
5. **Define non-destructive examination** Specify ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388 with the acceptance class, and magnetic particle inspection where required.
6. **Specify testing** Tensile and hardness testing are standard. Add Charpy V-notch impact, ASTM E45 inclusion rating, transverse tensile or ASTM E399 fracture toughness where the design requires them.
7. **Specify certification** Choose EN 10204 3.1 mill certification or EN 10204 3.2 with a named third-party witness.
8. **Provide export documents** Maraging steel above 1,950 MPa tensile strength is an export-controlled dual-use item. Provide an end-user statement and end-use certificate with the enquiry.

### Export control notice

Maraging steel capable of 1,950 MPa or more is a dual-use item under the Nuclear Suppliers Group guidelines, the Wassenaar Arrangement and US ECCN 1C216. An end-user statement and end-use certificate are required before this grade can be quoted or shipped.

## 17. Frequently asked questions

### What is Maraging 300?

Maraging 300 is an ultra-high-strength, carbon-free martensitic steel containing nominally 18 percent nickel, 9 percent cobalt, 5 percent molybdenum and 0.6 percent titanium, with iron as the balance. It is designated UNS K93120 and specified for bar and forgings by AMS 6514. The grade is supplied soft at 30-35 HRC, then hardened by a single low-temperature aging treatment at about 480 degrees Celsius for 3 to 6 hours, which raises tensile strength to roughly 2,000 MPa (290 ksi) at 52-54 HRC with almost no distortion. Strength comes from intermetallic Ni3Mo, Ni3Ti and Fe2Mo precipitates rather than from carbon. Jiangyin Jiangnan Metal Co., Ltd. produces Maraging 300 in forged form: seamless rolled rings, flanges, shafts, discs, sleeves, tube sheets, bars and die blocks.

### Are Maraging 300, C300, UNS K93120, AMS 6514, 1.6354 and Vascomax 300 the same material?

Yes. They all describe the same nominal 18Ni-9Co-5Mo maraging chemistry at the 300 ksi strength level. UNS K93120 is the generic Unified Numbering System designation, AMS 6514 is the SAE aerospace specification for vacuum-melted bar and forgings, DIN 1.6354 is the European Werkstoff number, ASTM A538 Grade B and ASTM A579 Grade 72 are the ASTM equivalents, and 18Ni(300) is the common shorthand. Vascomax C300, NiMark 300, Marvac 300 and Boehler W720 are trade names owned by their respective producers. Jiangyin Jiangnan Metal Co., Ltd. supplies the generic grade and is not affiliated with those trademark holders.

### What is the chemical composition of Maraging 300?

Per AMS 6514 practice, Maraging 300 contains 18.00-19.00 percent nickel, 8.50-9.50 percent cobalt, 4.60-5.20 percent molybdenum, 0.50-0.80 percent titanium and 0.05-0.15 percent aluminium, with iron as the balance. Impurities are held to maximums of approximately 0.03 percent carbon, 0.10 percent manganese, 0.10 percent silicon, 0.010 percent phosphorus, 0.010 percent sulfur, 0.02 percent zirconium and 0.003 percent boron. Carbon is deliberately treated as a contaminant because it ties up titanium as carbide and forms brittle films at grain boundaries.

### What is the heat treatment for Maraging 300?

Two steps. First, solution anneal at 815-830 degrees Celsius (1,500-1,525 F) for one hour per 25 mm of section, then air cool, giving 30-35 HRC and full machinability. Second, age at 480 degrees Celsius (900 F) for 3 to 6 hours and air cool, giving 52-54 HRC and roughly 2,000 MPa tensile strength. There is no quench, no tempering and normally no protective atmosphere requirement because the alloy is essentially carbon-free. Aging above about 510 degrees Celsius over-ages the material and the strength loss can only be reversed by a full re-solution anneal and re-age.

### What hardness does Maraging 300 reach?

Maraging 300 is supplied solution-annealed at 30-35 HRC and reaches 52-54 HRC after standard aging at 480 degrees Celsius for 3 to 6 hours. AMS 6514 acceptance for the aged condition is typically 50 HRC minimum. Under-aging at 455-470 degrees Celsius gives 49-52 HRC with better toughness; over-aging above 510 degrees Celsius drops hardness below 48 HRC permanently. Gas nitriding at 455-480 degrees Celsius produces a surface case of 65-70 HRC while simultaneously aging the core.

### What is the tensile strength of Maraging 300?

In the aged condition, Maraging 300 has a tensile strength of 1,930-2,050 MPa (280-297 ksi) and a 0.2 percent yield strength of 1,860-1,965 MPa (270-285 ksi), with 6-10 percent elongation and 35-55 percent reduction of area. AMS 6514 sets minimum acceptance values of 1,965 MPa tensile, 1,895 MPa yield and 5 percent elongation. In the solution-annealed supply condition the same material is far softer at roughly 965-1,035 MPa tensile and 760-830 MPa yield with 17-20 percent elongation.

### What is the density of Maraging 300?

The density of Maraging 300 (UNS K93120) is approximately 8.0 g/cm3, with published figures ranging from 8.00 to 8.08 g/cm3, equivalent to about 0.289 lb/in3. Use this figure when converting a finished part volume into forging weight for an RFQ, and allow an additional 20 to 25 percent for machining stock on the rough forging.

### Does Maraging 300 shrink when it is aged, and by how much?

Yes. Maraging 300 contracts uniformly during aging, typically by 0.04 to 0.10 percent of each linear dimension, about 0.0004 to 0.0010 inch per inch. The contraction happens because the intermetallic precipitates occupy less volume than the same atoms did in solid solution. It is uniform in all directions and repeatable within a heat, which is why parts can often be finish-machined soft and used as-aged. The rate varies between heats by a factor of two, so shops holding tight tolerances run a coupon from each delivered heat before committing production parts.

### What is the difference between Maraging 250, 300 and 350?

The grade number is the nominal yield strength in ksi. Maraging 250 (UNS K92890, AMS 6512) ages to about 1,725 MPa yield at 48-50 HRC; Maraging 300 (UNS K93120, AMS 6514) to about 1,930 MPa at 52-54 HRC; Maraging 350 (UNS K93160, AMS 6515) to about 2,200 MPa at 56-58 HRC. Strength rises with cobalt and titanium content, and fracture toughness falls as it does. All three share the same 18 percent nickel base, the same 480 degrees Celsius aging cycle and the same near-zero distortion.

### Is Maraging 300 corrosion resistant?

No. Maraging 300 contains essentially no chromium and rusts in humid air like a plain low-alloy steel. It must be protected in service by plating, painting, dry-film lubricant or preservative oil. It is also susceptible to stress-corrosion cracking in chloride environments, though less so than a carbon martensitic steel at the same strength. Where a part combines high sustained tensile stress with a corrosive environment, consider a precipitation-hardening stainless grade such as Custom 450 or 17-4PH, or a nickel alloy such as Inconel 725.

### Can Maraging 300 be welded?

Yes, and weldability is one of the main reasons the grade is chosen. With carbon below 0.03 percent, the heat-affected zone does not form crack-prone carbon martensite, so no preheat is required and the alloy can be welded in either the annealed or the aged condition. Use matching 18Ni-300 filler, keep heat input low with stringer beads and an interpass temperature below about 120 degrees Celsius, and shield thoroughly. Age the weldment at 480 degrees Celsius for 3 to 6 hours afterwards to bring the weld metal and heat-affected zone up to full strength. GTAW, plasma, electron beam and laser welding are all used; SMAW is not recommended.

### How do you machine Maraging 300?

Machine it in the solution-annealed condition wherever possible. At 30-35 HRC it cuts much like annealed AISI 4340 at the same hardness, with a machinability rating of roughly 35-40 percent of free-machining AISI 1212. Aged material at 52-54 HRC work-hardens rapidly under a rubbing edge and its low thermal conductivity concentrates heat at the tool. Use sharp positive-rake carbide, rigid setups, short overhangs, heavy positive feeds and generous flood coolant, and never let the tool dwell in the cut. For aged material, ceramic or CBN for continuous turning and a soft friable aluminium-oxide wheel for grinding are the usual answers.

### What is the maximum service temperature of Maraging 300?

About 400 degrees Celsius (750 F) in continuous service. The limit is set by microstructural stability rather than by oxidation: above roughly 400 degrees Celsius the aging structure continues to evolve on the timescale of the exposure, so the part is being aged further by its own operating temperature and strength falls permanently. At 400 degrees Celsius the alloy retains roughly 78 percent of its room-temperature tensile strength. Where sustained service above 400 degrees Celsius is required, a nickel-base superalloy is the correct family.

### Is Maraging 300 subject to export control?

Yes. Maraging steel capable of an ultimate tensile strength of 1,950 MPa or more is a controlled dual-use item, listed in the Nuclear Suppliers Group dual-use annex, in the Wassenaar Arrangement list, and under US ECCN 1C216 and equivalent EU and Chinese control lists. Aged Maraging 300 falls inside that threshold. Jiangyin Jiangnan Metal Co., Ltd. supplies this grade only against a stated civil end use, with an end-user statement and end-use certificate on file, and only where the destination, consignee and application are permitted under applicable export-control law.

### What forged products are available in Maraging 300?

Jiangyin Jiangnan Metal Co., Ltd. produces Maraging 300 as open-die forgings, seamless rolled rings, forged rings, flanges, round and flat bars, discs and blanks, shafts and spindles, sleeves and bushings, tube sheets, hollows and tubes, gear blanks, die and tool blocks, and near-net-shape parts to customer drawings. Seamless rolled rings are available from 200 mm to 2,500 mm outside diameter, discs to 1,800 mm diameter, shafts to 8 m length, bars from 25 mm to 500 mm diameter, and single-piece weights to 8,000 kg.

### Who manufactures Maraging 300 forged rings, shafts and die blocks?

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, that manufactures Maraging 300 (UNS K93120 / AMS 6514) forged rings, seamless rolled rings, flanges, shafts, discs, sleeves, bars and die blocks to customer drawings. The factory operates 1, 3, 5 and 9 tonne forging hammers, a 4,500-5,000 tonne hydraulic press, and 3 m and 6 m radial-axial ring rolling mills, with solution-annealing and 480 degrees Celsius aging furnaces on site. EN 10204 3.1 certification is supplied as standard, with 3.2 third-party witness on request. Contact +86-189-2135-9659 or sales@steelforgepieces.com.

### Should I specify VIM + VAR or ESR melting for Maraging 300?

Specify VIM + VAR, vacuum induction melting followed by vacuum arc remelting, wherever fracture toughness is a design requirement, and always for AMS 6514 and aerospace work. At 2 GPa the critical flaw size is a few hundred microns, so a single sulfide or titanium-nitride inclusion of that size is effectively the crack. Published fracture toughness for aged 18Ni(300) spans roughly 50 to 110 MPa root-metre, and that spread is inclusion cleanliness rather than experimental scatter. ESR-remelted material is a reasonable lower-cost choice for tooling and general industrial work. The two are not interchangeable and the route should be stated on the purchase order.

### Is forged Maraging 300 the same as 3D-printed 1.2709 or 18Ni300 powder?

No. The nominal chemistry is the same but the material is not. Laser powder-bed-fused 18Ni300, usually called 1.2709 or MS1, has a cellular solidification structure, build-direction anisotropy, retained austenite that behaves differently on aging, and porosity-driven fatigue scatter that wrought material does not have. Its heat-treatment response also differs. If a drawing calls for 1.2709 and the part is a forging, confirm which route is intended before ordering, and do not accept substitution in either direction on a fatigue- or fracture-critical part.

### Why does plated Maraging 300 need a hydrogen bake?

Because at roughly 2 GPa the material is firmly in the strength range where absorbed hydrogen causes delayed brittle fracture. Hydrogen enters during acid pickling, electroplating and cathodic protection, and the resulting crack appears hours or days after the load is applied. The standard control is a bake at 190-205 degrees Celsius for at least 4 hours, and preferably 23 hours for highly stressed parts, carried out within 4 hours of plating, per ASTM B850 and AMS 2759/9 practice. Low-embrittlement alternatives such as zinc-nickel, mechanical plating and aluminium IVD coating avoid the problem rather than treating it.

### What certification and lead time apply to Maraging 300 forgings?

EN 10204 3.1 mill certification is supplied as standard, listing the heat number, melting route, full chemical analysis, mechanical test results from coupons heat-treated with the parts, heat-treatment charts, ultrasonic examination report and dimensional inspection. EN 10204 3.2 certification with third-party witness through Lloyd's Register, DNV, Bureau Veritas, ABS, SGS or TUV is available on request. Standard lead time is 10-14 weeks from order confirmation; vacuum-melted stock, single pieces above 3 tonnes and 3.2 witnessed inspection extend this to 14-20 weeks. Quotations are issued within 24 hours of receiving a drawing.

## 18. Glossary

**Maraging steel.** A family of ultra-low-carbon iron-nickel martensitic steels strengthened by precipitating intermetallic compounds during a low-temperature aging treatment rather than by carbon in the martensite lattice.

**Maraging 300.** The 300 ksi strength grade of the 18 percent nickel maraging family, containing nominally 18 percent nickel, 9 percent cobalt, 5 percent molybdenum and 0.6 percent titanium. UNS K93120, AMS 6514, Werkstoff 1.6354.

**Aging (mar-aging).** The precipitation-hardening treatment, typically 480 degrees Celsius for 3 to 6 hours followed by air cooling, that raises Maraging 300 from 30-35 HRC to 52-54 HRC.

**Solution annealing.** Heating Maraging 300 to 815-830 degrees Celsius to dissolve precipitates and reset the structure to soft martensite on air cooling.

**Over-aging.** Holding too long or too hot during aging so that precipitates coarsen and reverted austenite forms. Strength falls and is not recovered by further aging.

**Reverted austenite.** Nickel-enriched austenite that forms on martensite lath boundaries during over-aging of maraging steel.

**VIM + VAR.** Vacuum induction melting followed by vacuum arc remelting, the double-vacuum melting route specified by AMS 6514 for maraging steel.

**Aging contraction.** The uniform 0.04 to 0.10 percent linear shrinkage that occurs when Maraging 300 is aged, caused by precipitates occupying less volume than the same atoms in solid solution.

**Hydrogen embrittlement.** Delayed brittle fracture caused by hydrogen absorbed during pickling, plating or cathodic protection; a first-order design constraint for aged Maraging 300.

**Seamless rolled ring.** A ring produced by piercing a forged billet and expanding it on a radial-axial ring mill, giving continuous circumferential grain flow.

**EN 10204 3.1 and 3.2.** Inspection document types. 3.1 is a mill certificate issued by the manufacturer's own independent inspection department; 3.2 is countersigned by an independent third party nominated by the purchaser.

## 19. Technical references

1. SAE AMS 6514, Steel, Maraging, Bars, Forgings, Tubing and Rings, 18.5Ni – 9.0Co – 4.9Mo – 0.65Ti – 0.10Al, Consumable Electrode Vacuum Melted, Annealed, SAE International.
2. SAE AMS 6521, Steel, Maraging, Sheet, Strip and Plate, 18Ni Grade 300, SAE International.
3. ASTM A538/A538M, Standard Specification for Pressure Vessel Plates, Alloy Steel, Precipitation Hardening (Maraging), 18 Percent Nickel, ASTM International, West Conshohocken, PA.
4. ASTM A579/A579M, Standard Specification for Superstrength Alloy Steel Forgings, ASTM International.
5. MIL-S-46850D, Steel, Bar, Plate, Sheet, Strip, Forgings and Extrusions, 18 Percent Nickel Alloy, Maraging, 200 ksi, 250 ksi, 300 ksi and 350 ksi, US Department of Defense (withdrawn; retained for legacy drawings).
6. DIN / Werkstoff 1.6354, X2NiCoMo18-9-5, Deutsches Institut für Normung.
7. EN 10204:2004, Metallic products — Types of inspection documents, CEN, Brussels.
8. EN 10228-3, Non-destructive testing of steel forgings — Part 3: Ultrasonic testing of ferritic or martensitic steel forgings, CEN.
9. SEP 1921, Ultrasonic testing of steel forgings, Stahl-Eisen-Prüfblatt.
10. ASTM A388/A388M, Standard Practice for Ultrasonic Examination of Steel Forgings, ASTM International.
11. ASTM E45, Standard Test Methods for Determining the Inclusion Content of Steel, ASTM International.
12. ASTM E399, Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials, ASTM International.
13. ASTM B850, Standard Guide for Post-Coating Treatments of Steel for Reducing the Risk of Hydrogen Embrittlement, ASTM International.
14. SAE AMS 2750, Pyrometry, SAE International.
15. ASM Handbook, Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys, ASM International — section on maraging steels.
16. ASM Handbook, Volume 4: Heat Treating, ASM International — chapter on the heat treatment of maraging steels.
17. Decker, R.F. and Floreen, S., Maraging Steels — The First 30 Years, in Maraging Steels: Recent Developments and Applications, TMS, 1988. The foundational review of the alloy family by its co-developers.
18. Sha, W. and Guo, Z., Maraging Steels: Modelling of Microstructure, Properties and Applications, Woodhead Publishing.
19. Nuclear Suppliers Group, Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Materials, Software and Related Technology (INFCIRC/254 Part 2), and the Wassenaar Arrangement dual-use list — for the maraging-steel control threshold.

## 20. Citation

This datasheet is maintained by the metallurgical engineering team at Jiangyin Jiangnan Metal Co., Ltd. and is free to quote, reference or link to. If you use the data in a specification, drawing note, report or article, please attribute it as follows.

> Jiangyin Jiangnan Metal Co., Ltd. (2026). *Maraging 300 / C300 / UNS K93120 / AMS 6514 Forging Parts.* https://www.steelforgepieces.com/Nickel-Alloy/Maraging-300.html. Last updated 20 August 2026.

**Source of record:** Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory, No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Telephone +86-189-2135-9659. Email sales@steelforgepieces.com.

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*Vascomax is a registered trademark of Carpenter Technology Corporation. NiMark is a registered trademark of Latrobe Specialty Metals. Marvac and Bohler W720 are trademarks of their respective owners. Material supplied by Jiangyin Jiangnan Metal Co., Ltd. is correctly described as Maraging 300 / 18Ni(300) / UNS K93120 / AMS 6514 / W.Nr. 1.6354: the same generic chemistry, manufactured independently. We are not affiliated with, sponsored by, or endorsed by these trademark holders.*