Titanium Grade 5 vs Grade 2: When to Use Each Alloy Type

Titanium alloys offer exceptional strength-to-weight ratios and corrosion resistance, but selecting between commercially pure (CP) titanium Grade 2 and the workhorse alpha-beta alloy Grade 5 (Ti-6Al-4V) requires understanding their fundamental differences. Each serves distinct engineering applications where their unique properties provide optimal performance.

Composition and Microstructure Differences

Titanium Grade 2 (CP Titanium):

Titanium: 99.2% minimum
Iron: 0.30% max
Oxygen: 0.25% max
Nitrogen: 0.03% max
Carbon: 0.08% max

Grade 2 represents unalloyed titanium with a single-phase alpha microstructure, providing excellent formability and weldability. Unlike complex alloy systems such as Hastelloy C276 or Alloy 625, Grade 2’s simplicity delivers reliable performance across diverse applications.

Titanium Grade 5 (Ti-6Al-4V):

Titanium: Balance (approximately 90%)
Aluminum: 5.5-6.75%
Vanadium: 3.5-4.5%
Iron: 0.30% max
Oxygen: 0.20% max

The aluminum and vanadium additions create a two-phase alpha-beta microstructure, dramatically increasing strength while maintaining reasonable ductility and corrosion resistance.

Mechanical Properties Comparison

Strength Performance:

Grade 2 Yield Strength: 275 MPa minimum
Grade 5 Yield Strength: 880 MPa minimum

This three-fold strength advantage makes Grade 5 competitive with high-strength alloys like Duplex 2205 while offering superior corrosion resistance and lower density (4.43 g/cm³ vs 7.8 g/cm³).

Ductility and Formability: Grade 2 exhibits superior elongation (20% minimum) compared to Grade 5 (10% minimum), enabling complex forming operations and tight-radius bending. This characteristic makes Grade 2 ideal for fabricated chemical equipment, similar to how Monel 400 excels in formed components.

Temperature Capability: Grade 5 maintains strength to approximately 400°C, while Grade 2 shows significant strength reduction above 200°C. For elevated temperature applications requiring superior corrosion resistance, Alloy 625 often proves more suitable.

Corrosion Resistance Analysis

Both grades demonstrate excellent corrosion resistance in oxidizing and mildly reducing environments, forming stable titanium dioxide (TiO₂) passive films. However, subtle differences influence material selection:

Grade 2 Advantages:

Superior resistance in reducing acids (hydrochloric, sulfuric) at moderate temperatures
Better performance in hydrogen sulfide environments
Lower susceptibility to hydrogen embrittlement
Excellent resistance in chlorinated organic compounds

Grade 5 Considerations: While Grade 5 maintains good general corrosion resistance, the alloying elements (aluminum, vanadium) can affect performance in specific media:

Slightly reduced resistance in strong reducing acids compared to Grade 2
Potential for selective attack in certain hot salt environments
Generally suitable for most atmospheric and natural water applications

For severe chemical environments, Hastelloy C276 provides superior resistance, though at significantly higher density and cost.

Application-Specific Recommendations

Choose Titanium Grade 2 for:

Chemical Processing Equipment:

Reactors and vessels handling oxidizing acids (nitric acid, chromic acid)
Heat exchangers in chloride-containing process streams
Piping systems in chlorine production facilities
Electroplating and metal finishing equipment

Marine Applications:

Desalination plant components
Offshore platform seawater systems (competing with Monel 400)
Subsea fasteners and hardware in non-structural applications
Aquaculture containment systems

Choose Titanium Grade 5 for:

Aerospace Applications:

Airframe structural components
Engine compressor blades and discs
Landing gear components
Fasteners requiring high strength-to-weight ratio

Medical Devices:

Orthopedic implants (hips, knees, spinal hardware)
Surgical instruments
Dental implants
Biocompatible fasteners

High-Performance Industrial:

Centrifuge components in chemical processing
Pressure vessels requiring weight reduction
Valve stems and springs in corrosive service
Sports equipment and recreational products

Fabrication and Welding

Grade 2 welds easily using GTAW with minimal heat-affected zone concerns. The single-phase microstructure maintains properties across welds, similar to the forgiving nature of annealed 316 stainless steel.

Grade 5 requires more careful welding control to prevent embrittlement and maintain ductility. Porosity prevention demands high-purity shielding gases and backing protection. Post-weld stress relief at 595-675°C for 1-2 hours optimizes properties in critical applications.

Both grades machine significantly differently than steel, requiring sharp tools, slower cutting speeds, and continuous coolant application to prevent work hardening—characteristics shared with Hastelloy C276 and other nickel alloys.

Cost Considerations

Grade 2 typically costs 20-30% less than Grade 5 due to simpler composition and processing. However, total cost analysis must consider:

Material utilization (Grade 5’s higher strength enables thinner sections)
Fabrication complexity (Grade 2’s superior formability reduces labor)
Service life and maintenance costs
Application-specific performance requirements

For applications where Duplex 2205 provides sufficient corrosion resistance and strength at lower cost, titanium may not justify its premium pricing despite weight advantages.

Conclusion

Select Titanium Grade 2 for maximum corrosion resistance, formability, and weldability in chemical processing and marine environments where moderate strength suffices. Choose Grade 5 for aerospace, medical, and high-performance applications requiring exceptional strength-to-weight ratios alongside good corrosion resistance. Understanding how these titanium grades compare to alternatives like Hastelloy C276, Duplex 2205, and Monel 400 ensures optimal material selection for your specific requirements.

FAQs

What is the difference between Titanium Grade 5 and Grade 2?

Titanium Grade 5 (Ti-6Al-4V) is an alloyed titanium containing aluminum and vanadium, offering very high strength.

Titanium Grade 2 is commercially pure titanium, known for excellent corrosion resistance and formability.

Which titanium grade is stronger: Grade 5 or Grade 2?

Titanium Grade 5 is significantly stronger than Grade 2, with nearly double the tensile and yield strength, making it ideal for high-load and structural applications.

Which titanium grade has better corrosion resistance?

Titanium Grade 2 has slightly better corrosion resistance than Grade 5, especially in chemical processing and marine environments, due to its high purity.

When should I use Titanium Grade 5?

Use Titanium Grade 5 when: