Nitralloy 135 Steel: Properties and Key Applications
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Table Of Content
Table Of Content
Nitralloy 135 Steel is a medium-carbon alloy steel specifically designed for applications requiring high strength and toughness. Classified as an alloy steel, it primarily contains elements such as chromium, molybdenum, and nitrogen, which significantly enhance its mechanical properties and performance characteristics. The incorporation of these alloying elements contributes to improved hardenability, wear resistance, and fatigue strength, making Nitralloy 135 suitable for demanding engineering applications.
One of the most significant characteristics of Nitralloy 135 is its ability to achieve high surface hardness through nitriding, a heat treatment process that diffuses nitrogen into the surface of the steel. This results in a hard, wear-resistant surface while maintaining a tough core, which is essential for components subjected to high stress and wear.
Advantages and Limitations
Advantages:
- High Strength and Toughness: Nitralloy 135 exhibits excellent tensile strength and impact resistance, making it ideal for heavy-duty applications.
- Nitriding Capability: The ability to undergo nitriding enhances surface hardness without compromising core toughness.
- Good Machinability: This steel grade can be machined effectively, allowing for precise component fabrication.
Limitations:
- Cost: The alloying elements and nitriding process can make Nitralloy 135 more expensive than standard carbon steels.
- Weldability Issues: While it can be welded, special care must be taken to avoid cracking and ensure joint integrity.
Historically, Nitralloy 135 has been utilized in various industries, including automotive and aerospace, where high-performance components are critical. Its unique properties position it as a valuable material in the market, particularly for applications requiring a combination of strength, toughness, and wear resistance.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | G13500 | USA | Closest equivalent to AISI 4140 with minor compositional differences. |
| AISI/SAE | 135 | USA | Commonly used designation in North America. |
| ASTM | A829 | USA | Standard specification for alloy steel plates. |
| EN | 1.8510 | Europe | European equivalent with similar properties. |
| JIS | SCr 440 | Japan | Similar performance but with different alloying elements. |
The differences between these grades can affect selection based on specific application requirements. For instance, while G13500 and AISI 4140 are similar, the nitriding capability of Nitralloy 135 provides enhanced surface hardness that may not be achievable with AISI 4140.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.30 - 0.35 |
| Cr (Chromium) | 0.80 - 1.10 |
| Mo (Molybdenum) | 0.15 - 0.25 |
| N (Nitrogen) | 0.02 - 0.05 |
| Mn (Manganese) | 0.60 - 0.90 |
| Si (Silicon) | 0.15 - 0.40 |
| P (Phosphorus) | ≤ 0.035 |
| S (Sulfur) | ≤ 0.025 |
The primary alloying elements in Nitralloy 135 play crucial roles:
- Chromium: Enhances hardenability and corrosion resistance.
- Molybdenum: Improves strength at elevated temperatures and enhances toughness.
- Nitrogen: Increases surface hardness through nitriding, contributing to wear resistance.
Mechanical Properties
| Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|---|
| Tensile Strength | Quenched & Tempered | Room Temp | 850 - 1000 MPa | 123 - 145 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Quenched & Tempered | Room Temp | 600 - 800 MPa | 87 - 116 ksi | ASTM E8 |
| Elongation | Quenched & Tempered | Room Temp | 12 - 18% | 12 - 18% | ASTM E8 |
| Hardness (HRC) | Quenched & Tempered | Room Temp | 30 - 40 HRC | 30 - 40 HRC | ASTM E18 |
| Impact Strength (Charpy) | Room Temp | -20°C | 30 - 50 J | 22 - 37 ft-lbf | ASTM E23 |
The combination of high tensile and yield strength, along with good elongation, makes Nitralloy 135 suitable for applications that require resistance to mechanical loading and structural integrity. Its hardness allows it to withstand wear in demanding environments.
Physical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | - | 7.85 g/cm³ | 0.284 lb/in³ |
| Melting Point | - | 1425 - 1540 °C | 2600 - 2800 °F |
| Thermal Conductivity | 20°C | 45 W/m·K | 31.2 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | 20°C | 0.46 kJ/kg·K | 0.11 BTU/lb·°F |
| Electrical Resistivity | 20°C | 0.00065 Ω·m | 0.00038 Ω·in |
Key physical properties such as density and melting point are significant for applications involving high-temperature operations. The thermal conductivity indicates how well the material can dissipate heat, which is crucial in high-speed machining or high-friction applications.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 3-5 | 25°C/77°F | Fair | Risk of pitting corrosion. |
| Sulfuric Acid | 10-20 | 25°C/77°F | Poor | Not recommended. |
| Alkaline Solutions | 5-10 | 25°C/77°F | Good | Moderate resistance. |
Nitralloy 135 exhibits moderate corrosion resistance, particularly in alkaline environments, but is susceptible to pitting in chloride-rich conditions. Compared to stainless steels, such as AISI 304, which offer superior corrosion resistance, Nitralloy 135 may not be suitable for applications exposed to aggressive corrosive agents.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 400°C | 752°F | Suitable for prolonged exposure. |
| Max Intermittent Service Temp | 500°C | 932°F | Short-term exposure only. |
| Scaling Temperature | 600°C | 1112°F | Risk of oxidation above this temp. |
At elevated temperatures, Nitralloy 135 maintains its strength but may experience oxidation if exposed to air. It is essential to consider protective coatings or controlled environments for applications involving high temperatures.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| MIG | ER70S-6 | Argon/CO2 mix | Preheat recommended. |
| TIG | ER80S-Ni | Argon | Requires post-weld heat treatment. |
Nitralloy 135 can be welded using standard processes, but preheating is often necessary to prevent cracking. Post-weld heat treatment is recommended to relieve stresses and improve toughness.
Machinability
| Machining Parameter | Nitralloy 135 | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60 | 100 | Requires sharp tools and coolant. |
| Typical Cutting Speed | 30 m/min | 50 m/min | Adjust based on tool wear. |
Machinability is good but requires careful attention to tooling and cutting conditions to avoid excessive wear.
Formability
Nitralloy 135 exhibits moderate formability. Cold forming is feasible, but hot forming is preferred to reduce the risk of work hardening. Recommended bend radii should be adhered to in order to avoid cracking.
Heat Treatment
| Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Annealing | 700 - 800 °C / 1292 - 1472 °F | 1-2 hours | Air or oil | Softening, improved machinability. |
| Quenching | 850 - 900 °C / 1562 - 1652 °F | 30 minutes | Oil | Hardening, increased strength. |
| Tempering | 400 - 600 °C / 752 - 1112 °F | 1 hour | Air | Reducing brittleness, improving toughness. |
The heat treatment processes significantly alter the microstructure of Nitralloy 135, enhancing its mechanical properties. Quenching increases hardness, while tempering helps to relieve stresses and improve ductility.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Automotive | Gears and shafts | High strength, toughness, wear resistance | Essential for durability. |
| Aerospace | Landing gear components | High strength-to-weight ratio | Critical for safety and performance. |
| Machinery | Tooling and dies | Hardness, machinability | Precision required for operation. |
Other applications include:
- Oil and gas: Components exposed to high stress and wear.
- Heavy machinery: Parts requiring high fatigue resistance.
Nitralloy 135 is chosen for these applications due to its unique combination of strength, toughness, and wear resistance, making it ideal for components that must endure harsh operating conditions.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | Nitralloy 135 | AISI 4140 | 8620 | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High Strength | Moderate | Moderate | Nitralloy 135 excels in strength. |
| Key Corrosion Aspect | Moderate | Fair | Good | Nitralloy 135 is less corrosion-resistant. |
| Weldability | Moderate | Good | Good | Requires care to avoid cracking. |
| Machinability | Good | Excellent | Fair | Requires specific tooling. |
| Formability | Moderate | Good | Good | Hot forming preferred. |
| Approx. Relative Cost | Higher | Moderate | Lower | Cost may be a factor in selection. |
| Typical Availability | Moderate | High | High | Availability can vary by region. |
When selecting Nitralloy 135, considerations include its cost-effectiveness relative to performance requirements, availability in the market, and specific application needs. Its unique properties make it suitable for high-performance applications, but potential users should weigh the benefits against the associated costs and fabrication challenges.
In conclusion, Nitralloy 135 is a versatile steel grade that offers a unique combination of strength, toughness, and wear resistance, making it an excellent choice for demanding engineering applications. Its properties, while advantageous, require careful consideration in terms of fabrication and application to maximize performance and longevity.
