What is the difference between AISI 321 and AISI 316Ti?

Both are titanium-stabilized austenitic stainless steels. AISI 321 (Russian 12Kh18N10T) is an 18/10 grade with about 0.4% titanium added to prevent intergranular corrosion after welding. AISI 316Ti (Russian 08Kh17N13M2T) is the molybdenum-containing version (about 2.5% Mo) with titanium stabilization, combining the pitting resistance of 316 with stabilization. 316Ti is used where both chlorides and welding/sensitization are concerns.

Why is titanium added to these grades?

Titanium has a stronger affinity for carbon than chromium. By tying up carbon as stable titanium carbides, it prevents chromium carbide precipitation at grain boundaries during welding or heating in the 425-815°C range, which would otherwise cause intergranular corrosion (sensitization).

Are 321 and 316Ti weldable?

Yes. Both are readily welded by TIG, MIG and MMA without post-weld heat treatment. The titanium stabilization avoids sensitization in the heat-affected zone, so they are preferred over non-stabilized 304/316 in welded structures exposed to corrosive or high-temperature service.

Which resists pitting in chlorides better?

316Ti, thanks to its 2.5% molybdenum, resists chloride pitting noticeably better than 321. 321 is not recommended for chloride-rich or marine environments where pitting is a risk.

What standards cover 321 and 316Ti?

AISI 321: ASTM A240/A312/A276, UNS S32100, Russian 12Kh18N10T (GOST 5632). AISI 316Ti: ASTM A240/A312/A276, UNS S31635, Russian 08Kh17N13M2T (GOST 5632).

In what forms are 321 and 316Ti supplied?

Both available as sheet, plate, bar, seamless and welded pipe, tube and forgings. Hangbo Alloy supplies both grades with EN 10204 3.1/3.2 certification.

AISI 321 (12Kh18N10T) vs AISI 316Ti (08Kh17N13M2T): Stabilized Stainless Steels

Q: Which resists intergranular corrosion better?

Both are equivalent in resisting intergranular corrosion because both are titanium-stabilized. 316Ti additionally offers better overall pitting resistance than 321 due to its molybdenum content.

Q: Which has better high-temperature performance?

Both are used in the 425-815°C range where unstabilized grades would sensitize. 321 and 316Ti are commonly selected for exhaust systems, heat exchangers and high-temperature ducting up to about 850-900°C. 316Ti retains slightly better strength at high temperature due to molybdenum.

AISI 321 (Russian grade 12Kh18N10T) and AISI 316Ti (Russian grade 08Kh17N13M2T) are titanium-stabilized austenitic stainless steels. Both were designed to resist intergranular corrosion after welding or exposure to the sensitization temperature range. 321 is an 18/10 chromium-nickel grade stabilized with titanium; 316Ti adds about 2.5% molybdenum to that stabilization, giving it the chloride pitting resistance of 316 plus immunity to sensitization. This article compares their composition, corrosion behaviour, welding and high-temperature use.

1. Chemical Composition

Element	AISI 321 (12Kh18N10T)	AISI 316Ti (08Kh17N13M2T)
C	≤0.08	≤0.08
Cr	17.0–19.0	16.5–18.5
Ni	9.0–12.0	11.0–14.0
Mo	—	2.0–3.0
Ti	≥5×C (≈0.4–0.7)	≥5×C (≈0.4–0.7)
Mn	≤2.0	≤2.0

Key difference: 316Ti contains 2–3% molybdenum that 321 lacks. Both carry titanium at roughly 5× the carbon content to bind carbon and prevent sensitization.

2. Mechanical Properties

Property	AISI 321	AISI 316Ti
Yield strength σ₀.₂, MPa	≥205	≥215
Tensile strength σᵦ, MPa	≥515	≥515
Elongation, %	≥40	≥40

3. Corrosion Resistance

Medium	AISI 321	AISI 316Ti	Recommendation
Intergranular corrosion (welded)	Excellent (stabilized)	Excellent (stabilized)	Both
Chloride pitting	Fair	Good (Mo)	316Ti
General corrosion	Good	Good+	316Ti
High-temperature oxidation	Good to ~850°C	Good to ~900°C	Both

4. Why Titanium Stabilization Matters

Titanium has a stronger affinity for carbon than chromium. By forming stable titanium carbides, it keeps carbon from precipitating as chromium carbides at grain boundaries during welding or heating in the 425–815°C (800–1500°F) range. Without stabilization, chromium depletion at the grain boundaries would cause intergranular corrosion (sensitization). This is why 321 and 316Ti are chosen over unstabilized 304/316 for welded structures in corrosive or high-temperature service.

5. Weldability

Parameter AISI 321 AISI 316Ti

Welding methods TIG, MIG, MMA TIG, MIG, MMA

Recommended filler ER321 ER316L or ER316Ti

Post-weld heat treatment Not required Not required

HAZ sensitization Avoided by Ti Avoided by Ti

Parameter	AISI 321	AISI 316Ti
Welding methods	TIG, MIG, MMA	TIG, MIG, MMA
Recommended filler	ER321	ER316L or ER316Ti
Post-weld heat treatment	Not required	Not required
HAZ sensitization	Avoided by Ti	Avoided by Ti

6. High-Temperature Service

Property	AISI 321	AISI 316Ti
Continuous service limit, °C	~850	~900
Typical uses	Exhaust, heat exchangers	Exhaust, ducts, headers

7. Applications

Industry	AISI 321	AISI 316Ti
Automotive / exhaust	Headers, manifolds	Headers, manifolds
Chemical / petrochemical	Welded tanks, piping	Welded tanks, chloride service
Aerospace	High-temp structures	High-temp structures
Power / heat exchangers	Superheater tubing	Superheater tubing

8. Conclusion

Need 321 or 316Ti?

Shanghai Hangbo Alloy Group supplies AISI 321 (12Kh18N10T) and AISI 316Ti (08Kh17N13M2T) in sheet, plate, bar, pipe and forgings with EN 10204 3.1/3.2 certification. Send your welding and service conditions for a recommendation.

📧 Email: serena@hangboalloy.com
📞 Tel: +86 166 2109 2936
💬 WhatsApp: +86 166 2109 2936

Criterion	Choose 321	Choose 316Ti
General stabilized service	✓ Cost-effective	Slightly higher
Chloride / pitting risk	Fair	✓ Better (Mo)
High-temp strength	Good	✓ Better
Welded + corrosive	✓ Stabilized	✓ Stabilized

Summary: Choose AISI 321 for general titanium-stabilized service where chlorides are absent. Choose AISI 316Ti when both molybdenum-level pitting resistance and titanium stabilization (for welded or high-temperature duty) are required.

9. Frequently Asked Questions (FAQ)

1. What is the difference between AISI 321 and 316Ti?

Both are titanium-stabilized austenitic stainless steels. 321 is an 18/10 grade; 316Ti adds about 2.5% molybdenum for chloride resistance while keeping titanium stabilization.

2. Why is titanium added?

Titanium binds carbon more strongly than chromium, preventing chromium carbide precipitation and intergranular corrosion in the 425–815°C range.

3. Which resists intergranular corrosion better?

Both are equal — both are titanium-stabilized. 316Ti additionally resists pitting better due to molybdenum.

4. Which has better high-temperature performance?

Both serve up to about 850–900°C; 316Ti retains slightly better strength because of molybdenum.

5. Are both weldable?

Yes. Both weld without post-weld heat treatment and avoid HAZ sensitization, making them preferable to unstabilized 304/316 in welded corrosive or high-temperature structures.

6. Which resists chloride pitting better?

316Ti, due to its 2.5% molybdenum, resists chloride pitting noticeably better than 321.

7. What standards cover these grades?

321: ASTM A240/A312/A276, UNS S32100, GOST 12Kh18N10T. 316Ti: ASTM A240/A312/A276, UNS S31635, GOST 08Kh17N13M2T.

8. In what forms are they supplied?

Both available as sheet, plate, bar, seamless/welded pipe, tube and forgings with EN 10204 certification.