Carbon Steel Seamless Pipe API 5L X65 Cladding Inconel 625 Weld
Overlay
A carbon steel seamless pipe with API 5L X65 base material and
Inconel 625 weld overlay cladding is a high-performance engineered
pipe designed for extreme environments, combining the strength of
carbon steel with the corrosion/erosion resistance of a
nickel-chromium alloy.
Key Specifications & Features
1. Base Material: API 5L X65 Seamless Pipe
- Grade: API 5L X65 (PSL1 or PSL2)
- Yield Strength:65,000 psi (448 MPa) min
- Manufacturing: Hot-rolled or cold-drawn seamless process (no
welds, superior pressure integrity).
- Applications: Oil & gas pipelines, downhole tubing, high-pressure
hydraulic systems.
2. Cladding: Inconel 625 Weld Overlay
- Alloy Composition (UNS N06625):
- Ni (58% min), Cr (20–23%), Mo (8–10%), Nb+Ta (3.15–4.15%)
- Resistant to pitting, chloride stress corrosion cracking (SCC),
and oxidation up to **1800°F (982°C).
Cladding Methods:
- Laser Cladding (Precision, Low Dilution)
- Submerged Arc Welding (SAW) or GTAW (TIG) Overlay
- Thermal Spray (Less Common for Pipes)
- Thickness: Typically 3–5 mm (customizable based on
corrosion/erosion needs).
Why Use Inconel 625 Over API 5L X65?
Corrosion Resistance: Protects against H₂S, CO₂, seawater, and
acidic fluids.
Erosion Resistance: Ideal for sand-laden fluids (e.g., fracking,
slurry transport).
High-Temp Performance: Maintains strength in refinery/petrochemical
heat exchangers.
Cost-Effective: Cheaper than solid Inconel 625 pipe but offers
similar protection.
Manufacturing Process
1. Pipe Production: Seamless API 5L X65 pipe is manufactured via
mandrel piercing/extrusion.
2. Surface Prep: Internal/external surface grit blasting/cleaning.
3. Cladding:*Inconel 625 is welded layer-by-layer (buttering
passes) to ensure metallurgical bonding.
4. Post-Weld Heat Treatment (PWHT): Optional stress relief (avoid
if base metal is cold-worked).
5. Inspection:
- UT/RT for weld integrity.
- Hardness Testing (avoid HAZ cracking).
- Dye Penetrant (PT) for surface defects.
Applications
- Oil & Gas
- Subsea pipelines (clad internally for sour service).
- Christmas trees, choke valves, risers.
- Chemical Processing: Acid transport, reactor liners.
- Power Plants: Boiler tubes, flue gas desulfurization (FGD)
systems.
- Mining:Slurry pipelines with abrasive/acidic media.
Challenges & Solutions
- Galvanic Corrosion Risk:*Insulate clad pipe from dissimilar
metals (e.g., CS flanges).
- Weld Defects: Strict NDT (radiographic testing) to ensure clad
adhesion.
- Thermal Expansion: Inconel 625 (~13.3 µm/m°C) vs. CS (~11.7
µm/m°C)—design for differential expansion.
