Why Bimetallic Cladding for Nickel Alloys?
Nickel alloys such as Inconel 625, Hastelloy C-276, Monel 400, and Alloy 200 offer outstanding corrosion resistance but come at a premium cost. Bimetallic cladding combines a thin layer of nickel alloy bonded to a carbon steel or low-alloy steel backing plate, delivering the corrosion resistance of the nickel alloy at a fraction of the cost of a solid nickel component.
Explosive Cladding (Explosion Bonding)
Process Description
- The base plate is placed on an anvil (sand bed or steel plate)
- Standoff distance is set between the base and cladding plates
- Explosive charge is placed on top of the cladding plate
- Detonation creates a high-velocity collision angle
- The collision creates a jet of metal that removes surface oxides
- Clean metal surfaces are forced together under extreme pressure (>1,000 MPa), creating a metallurgical bond
Key Parameters
- Detonation velocity: 2,000–3,500 m/s
- Collision velocity: Typically 200–500 m/s
- Standoff distance: 0.5–2× cladding thickness
- Bond interface: Characteristic wavy pattern
Advantages
- Can bond virtually any metal combination
- No heat input — no heat-affected zone, no dilution
- Large plate sizes possible (up to 5m × 15m or larger)
- Cladding thickness: 1.5mm to 50% of total plate thickness
- Excellent bond strength
- Suitable for field cladding of installed equipment
Limitations
- Lower production rate compared to roll bonding
- Environmental and safety concerns with explosive handling
- Not economical for thin-gauge sheet or high-volume production
- Some geometries (small diameter pipe) are not suitable
Roll Bonding (Hot Roll Cladding)
Process Description
- Surface preparation of both plates (grinding, shot blasting)
- Tack welding around edges to create sealed assembly
- Heating to bonding temperature (typically 900–1,200°C)
- Hot rolling through plate mill with 50–80% reduction
- Post-rolling: cooling, shearing, and heat treatment
Key Parameters
- Bonding temperature: 900–1,200°C
- Reduction ratio: 50–80%
- Rolling speed: 0.5–3 m/s
Advantages
- High production rate — suitable for large-volume orders
- Consistent bond quality across the entire plate
- Can produce thin cladding (0.5–2mm) with tight tolerance
- Lower cost per unit area for high-volume production
- Suitable for pipe and tube production (CRA-lined pipe)
Limitations
- Heat input causes dilution at the bond interface (typically 5–10%)
- Limited metal combinations
- Maximum plate size limited by mill capacity
- Not suitable for field repairs
Comparison: Explosive vs Roll Bonding
| Parameter | Explosive Cladding | Roll Bonding |
|---|---|---|
| Bond type | Mechanical + metallurgical (wavy) | Diffusion bond (flat) |
| Heat input | None (cold process) | High (900–1,200°C) |
| Cladding dilution | Minimal (<2%) | 5–10% typical |
| Plate size | Very large (up to 5×15m) | Limited by mill |
| Volume | Low to medium | High |
| Cost (volume) | Higher per unit | Lower per unit |
| Metal combinations | Almost unlimited | Limited by compatibility |
Bond Quality Inspection Methods
Non-Destructive Testing
- Ultrasonic Testing (UT): Primary method. 100% scanning per ASTM A578/A578M.
- Eddy Current Testing: For surface and near-surface defects in thin cladding.
Destructive Testing
- Shear test: Bond strength (minimum typically 140 MPa per AWS C2.4)
- Peel test: Evaluates bond ductility and toughness
- Macroscopic examination: Reveals bond interface morphology and dilution zone
Standards and Specifications
- ASTM A264/A265: Stainless steel-clad plate, sheet, and strip
- ASTM A578/A578M: Ultrasonic examination of rolled steel plates
- API 6ACR: CRA clad steel pipe
- NACE MR0175/ISO 15156: Materials for sour service
- AWS C2.4/C2.4M: Standard Guide for Explosion Welding
CoreMetal Steel — Nickel Alloy Clad Products
CoreMetal Steel supplies nickel alloy bimetallic clad plate and pipe in Inconel 625, Hastelloy C-276, and Monel 400 cladding over carbon steel backing. All products are ultrasonically tested per ASTM A578 and meet NACE MR0175 sour service requirements.
Email: tracy@coremetalsteel.com | Phone: +86 18291910632