UNS S38815 is a high-alloyed austenitic stainless steel designed for superior resistance to oxidation, sulfidation, and high-temperature corrosion. It belongs to the advanced group of stainless steels engineered for harsh environments where both strength and corrosion resistance are critical. This material provides an excellent balance of mechanical strength, creep resistance, and resistance to thermal fatigue, making it ideal for demanding industrial applications.

Introduction to UNS S38815

The UNS S38815 stainless steel grade is a specialized alloy that offers enhanced performance compared to standard grades like UNS S30815, UNS S31008, and UNS-S31603. It is particularly developed for use in conditions involving high temperatures and aggressive chemical exposure. The alloy’s microstructure consists mainly of stable austenite with controlled amounts of chromium, nickel, and nitrogen to improve oxidation resistance and mechanical stability.

UNS S38815 is widely recognized for its superior performance in applications such as heat exchangers, furnace components, boilers, and petrochemical processing equipment. Its advanced metallurgy makes it a reliable choice where lower-grade stainless steels may fail due to scaling or thermal degradation.

Key Features of UNS S38815

• Excellent High-Temperature Strength: Maintains mechanical stability even at temperatures above 1000°C.
• Superior Oxidation Resistance: Performs well under cyclic oxidation and thermal fatigue conditions.
• Enhanced Creep and Rupture Strength: Ensures long-term reliability under stress and heat.
• Good Weldability and Fabrication: Can be easily welded using conventional methods with minimal risk of cracking.
• Outstanding Corrosion Resistance: Protects against chloride-induced stress corrosion cracking and sulfur-bearing gases.

These features make uns 38815 a preferred choice for thermal processing and heat-resistant applications.

Comparison with Other Stainless Steel Grades

When compared with other popular stainless steel grades, UNS S38815 stands out for its exceptional resistance to high-temperature corrosion and scaling.

UNS S30815 (253 MA)

• Known for its excellent oxidation resistance and high strength at elevated temperatures.
• Contains nitrogen and rare earth metals for improved creep resistance.
• Commonly used in furnaces, kilns, and heat treatment equipment.

UNS S31008 (310S Stainless Steel)

• Offers superior oxidation and sulfidation resistance up to 1100°C.
• High chromium and nickel content provide structural stability at extreme temperatures.
• Used in burners, heat exchangers, and incineration plants.

UNS-S31603 (316L Stainless Steel)

• A low-carbon version of 316 stainless steel with enhanced resistance to pitting and crevice corrosion.
• Ideal for marine, pharmaceutical, and chemical industries.
• Not suitable for continuous high-temperature service compared to UNS S38815.

UNS-S31803 (Duplex 2205 Stainless Steel)

• A duplex stainless steel offering a mix of austenitic and ferritic properties.
• Provides excellent resistance to stress corrosion cracking and pitting.
• Commonly used in desalination plants, pressure vessels, and pipelines.

In comparison, UNS S38815 exceeds the performance of these grades when operating under continuous high temperatures, thermal cycling, or corrosive gaseous environments.

Chemical Composition of UNS S38815

Element

Composition (%)

Chromium (Cr)

24.0 – 26.0

Nickel (Ni)

18.0 – 22.0

Nitrogen (N)

0.15 – 0.20

Silicon (Si)

1.0 max

Manganese (Mn)

1.0 max

Carbon (C)

0.08 max

Sulfur (S)

0.03 max

Iron (Fe)

Balance

This balanced composition enhances strength and corrosion resistance while maintaining good formability and weldability.

Mechanical Properties

Property

Value

Tensile Strength

650 MPa min

Yield Strength (0.2% offset)

300 MPa min

Elongation

40% min

Hardness (HB)

210 max

These properties make UNS S38815 suitable for components exposed to both mechanical stress and thermal fluctuations.

Applications of UNS S38815

Due to its excellent combination of heat resistance and corrosion resistance, UNS S38815 is widely used in:

• Furnace and Heat Treatment Equipment: Radiant tubes, muffles, and fixtures.
• Petrochemical Industry: Reformer tubes, heat exchangers, and process piping.
• Power Generation: Boiler parts, superheater tubes, and exhaust components.
• Cement and Steel Plants: Kiln liners and recuperator tubes.
• Thermal Processing Systems: Combustion chambers, burners, and thermal oxidizers.

In all these applications, uns 38815 provides longer service life and reduced maintenance compared to lower alloy grades.

Fabrication and Welding

UNS S38815 can be fabricated using standard stainless steel practices. It has good weldability using TIG, MIG, and shielded metal arc welding techniques. Post-weld heat treatment is typically unnecessary unless the component will operate under severe stress or corrosive environments. The alloy can be hot or cold worked, but high forming temperatures are recommended to maintain ductility.

Corrosion and Heat Resistance

The high chromium and nickel content of UNS S38815 ensures exceptional oxidation resistance. Its stable oxide layer prevents scaling even during repeated thermal cycles. This property makes it superior to uns s30815, uns s31008, and uns-s31603 in long-term heat exposure. Additionally, the nitrogen addition enhances resistance to carburization and sulfidation, making it suitable for sulfur-rich atmospheres.

Conclusion

UNS S38815 stainless steel represents the next generation of heat-resistant alloys that bridge the gap between traditional austenitic and high