Overview
SAE/AISI 9310 Steel is a premium nickel-chromium-molybdenum carburizing alloy steel engineered for applications requiring exceptional fatigue strength, wear resistance, core toughness, and gear performance. It is considered one of the highest-performance case-hardening steels available and is widely used in aerospace, defense, motorsports, and heavy-duty transmission systems.
Compared with SAE 8620, SAE 9310 offers significantly higher fatigue strength, deeper hardenability, and superior core toughness due to its higher nickel content.
SAE 9310 is widely used in:
- Aerospace Gears
- Aircraft Transmission Systems
- Helicopter Gearboxes
- Racing Transmissions
- High-Performance Drivetrains
- Power Transmission Equipment
- Military Gear Systems
- Precision Mechanical Components
Because of its outstanding fatigue performance and carburizing response, SAE 9310 is often regarded as the benchmark material for high-performance gears.
Material Specification
| Property | Value |
|---|---|
| Material Designation | SAE/AISI 9310 |
| Standard | AMS 6260 / ASTM A534 |
| UNS Number | G93100 |
| Material Family | Nickel-Chromium-Molybdenum Alloy Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Standard Forms | Bar, Forgings, Gear Blanks, Plate, Shafting |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.08–0.13 |
| Nickel (Ni) | 3.00–3.50 |
| Chromium (Cr) | 1.00–1.40 |
| Molybdenum (Mo) | 0.08–0.15 |
| Manganese (Mn) | 0.45–0.65 |
| Silicon (Si) | 0.15–0.35 |
| Phosphorus (P) | ≤0.025 |
| Sulfur (S) | ≤0.025 |
The high nickel content significantly improves toughness, fatigue resistance, and deep hardening capability.
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | 620–760 MPa |
| Yield Strength | 380–550 MPa |
| Elongation | 18–28% |
| Hardness | 180–240 HB |
| Elastic Modulus | 205 GPa |
Quenched & Tempered Condition
| Property | Value |
|---|---|
| Tensile Strength | 900–1250 MPa |
| Yield Strength | 760–1100 MPa |
| Elongation | 12–20% |
| Hardness | 28–42 HRC |
Carburized Condition
| Property | Value |
|---|---|
| Surface Hardness | 58–65 HRC |
| Core Hardness | 30–45 HRC |
| Fatigue Resistance | Exceptional |
| Wear Resistance | Outstanding |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1415–1510°C |
| Thermal Conductivity | 38 W/m·K |
| Electrical Resistivity | 0.23 μΩ·m |
| Thermal Expansion Coefficient | 12.1 × 10⁻⁶/K |
| Specific Heat Capacity | 460 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Indoor Environment | Good |
| Dry Atmosphere | Good |
| Outdoor Environment | Moderate |
| Humid Environment | Moderate |
| Marine Environment | Poor |
| Chemical Environment | Poor |
SAE 9310 is not a corrosion-resistant alloy and requires protective treatments for long-term environmental exposure.
Recommended surface treatments:
- Carburizing
- Carbonitriding
- QPQ Treatment
- Black Oxide
- Electroless Nickel Plating
- Zinc Plating
- Phosphate Coating
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Moderate |
| MIG Welding | Moderate |
| Arc Welding | Moderate |
| Resistance Welding | Good |
| Spot Welding | Good |
Although weldable, SAE 9310 is typically used in highly stressed applications where welding is minimized.
Recommended:
- Preheating
- Controlled Cooling
- Post-Weld Heat Treatment
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Good |
| CNC Milling | Good |
| Drilling | Good |
| Grinding | Excellent |
| Gear Hobbing | Excellent |
| Broaching | Excellent |
Machinability Comparison
| Material | Machinability |
|---|---|
| 8620 | Excellent |
| 9310 | Good |
| 4140 | Good |
| 4340 | Good |
| Maraging Steel | Moderate |
9310 is generally machined before carburizing and final grinding.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 815–870°C |
| Cooling Method | Furnace Cool |
Normalizing
| Parameter | Value |
|---|---|
| Temperature | 870–925°C |
| Cooling Method | Air Cool |
Carburizing
| Parameter | Value |
|---|---|
| Temperature | 900–955°C |
| Case Depth | 0.5–2.5 mm |
| Surface Hardness | 58–65 HRC |
Quenching
| Parameter | Value |
|---|---|
| Temperature | 815–845°C |
| Cooling Medium | Oil |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 150–650°C |
| Purpose | Toughness Optimization |
Carbonitriding
| Property | Value |
|---|---|
| Surface Hardness | 60–66 HRC |
| Wear Resistance | Exceptional |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| SAE/AISI (USA) | 9310 |
| AMS | AMS 6260 |
| ASTM | ASTM A534 Grade 9310 |
| UNS | G93100 |
| GB/T (China) | Approx. 20CrNi3Mo |
| EN (Europe) | 18CrNiMo7-6 (Closest Equivalent) |
| DIN (Germany) | 1.6587 (Closest Equivalent) |
| JIS (Japan) | SNCM420 (Approximate Equivalent) |
Note: SAE 9310 has no exact international equivalent and is considered a specialized aerospace-grade carburizing steel.
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Forgings | Yes |
| Gear Blanks | Yes |
| Precision Ground Bar | Yes |
| Aerospace Grade Bar | Yes |
| Shaft Stock | Yes |
| Alloy Plate | Limited |
Typical Applications
Aerospace Industry
- Aircraft Gears
- Helicopter Transmission Gears
- Landing Gear Components
- Aerospace Drive Systems
Motorsport Industry
- Racing Transmission Gears
- Differential Components
- High-Performance Gearboxes
Defense Industry
- Military Gear Systems
- Power Transmission Components
- Precision Mechanical Assemblies
Industrial Power Transmission
- High-Speed Gears
- Heavy-Duty Pinions
- Planetary Gear Systems
Wind Energy Industry
- Gearbox Components
- High-Fatigue Transmission Parts
Robotics & Automation
- Precision Gear Sets
- High-Load Mechanical Systems
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Turning | Excellent |
| CNC Milling | Excellent |
| Gear Hobbing | Outstanding |
| Gear Shaping | Outstanding |
| Carburizing | Outstanding |
| Carbonitriding | Outstanding |
| Precision Grinding | Outstanding |
| Superfinishing | Outstanding |
Advantages
Exceptional Fatigue Resistance
One of the best gear steels available.
Outstanding Core Toughness
Resists shock and cyclic loading.
Excellent Carburizing Performance
Produces extremely wear-resistant surfaces.
Superior Gear Performance
Widely used in aerospace gearboxes.
High Contact Fatigue Strength
Excellent resistance to pitting and spalling.
Proven Aerospace Material
Used in critical flight components.
Limitations
Higher Material Cost
More expensive than 8620 and 4140.
Complex Heat Treatment
Requires controlled carburizing processes.
Limited Corrosion Resistance
Needs surface protection.
More Difficult Procurement
Not as widely stocked as common alloy steels.
Comparison with Other Alloy Steels
| Property | 9310 | 8620 | 4140 | 4340 | 18CrNiMo7-6 |
|---|---|---|---|---|---|
| Nickel Content | Very High | Moderate | None | High | High |
| Fatigue Strength | Exceptional | Excellent | Good | Outstanding | Outstanding |
| Carburizing Ability | Exceptional | Outstanding | Moderate | Moderate | Outstanding |
| Gear Performance | Exceptional | Excellent | Good | Excellent | Outstanding |
| Cost | High | Moderate | Moderate | High | High |
Comparison with Engineering Materials
| Material | Yield Strength | Surface Hardness | Fatigue Resistance |
|---|---|---|---|
| SAE 9310 | 760–1100 MPa | 58–65 HRC | Exceptional |
| SAE 8620 | 550–850 MPa | 58–64 HRC | Excellent |
| SAE 4340 | 740–1600 MPa | 60 HRC | Outstanding |
| 18CrNiMo7-6 | 700–1100 MPa | 60–64 HRC | Outstanding |
| Maraging Steel 300 | 1700–2000 MPa | 52 HRC | Exceptional |
| 17-4PH Stainless | 860–1170 MPa | 44 HRC | Excellent |
Available Surface Finishes
Raw Finishes
- Annealed Finish
- Normalized Finish
- Precision Machined Finish
- Ground Finish
Functional Finishes
- Carburized Finish
- Carbonitrided Finish
- Superfinished Gear Teeth
- Precision Ground Finish
Protective Finishes
- Black Oxide
- Electroless Nickel Plating
- Zinc Plating
- Phosphate Coating
- QPQ Treatment
Frequently Asked Questions (FAQ)
What is SAE 9310 steel?
SAE 9310 is a premium nickel-chromium-molybdenum alloy steel developed primarily for high-performance carburized gears and aerospace transmission systems.
What is SAE 9310 used for?
Typical applications include:
- Aerospace Gears
- Helicopter Gearboxes
- Racing Transmissions
- Differential Systems
- Military Drive Systems
What is the difference between SAE 9310 and SAE 8620?
| Property | SAE 9310 | SAE 8620 |
|---|---|---|
| Nickel Content | Higher | Lower |
| Fatigue Strength | Higher | Lower |
| Core Toughness | Better | Excellent |
| Aerospace Usage | Common | Limited |
Is SAE 9310 suitable for gears?
Yes. SAE 9310 is widely considered one of the best materials available for high-performance gears.
Can SAE 9310 be carburized?
Yes. It was specifically developed for carburizing and case-hardening applications.
What hardness can SAE 9310 achieve?
- Carburized Surface: 58–65 HRC
- Carbonitrided Surface: 60–66 HRC
Why is SAE 9310 used in aerospace gearboxes?
Because it combines:
- Exceptional Fatigue Strength
- Outstanding Core Toughness
- High Surface Hardness
- Excellent Wear Resistance
- Long Service Life
Is SAE 9310 better than 8620?
For critical gear applications, yes. SAE 9310 generally offers higher fatigue life and greater durability.
Can SAE 9310 be welded?
It can be welded, but welding is generally avoided for critical aerospace and drivetrain components.
Does GCNOV provide custom manufacturing services for SAE 9310?
Yes. GCNOV provides:
- CNC Turning
- CNC Milling
- Gear Manufacturing
- Gear Hobbing
- Carburizing
- Carbonitriding
- Precision Gear Grinding
- Superfinishing
- Prototype Development
- Low-Volume Production
- Mass Production