Clad welding and weld overlay metallurgically bond a corrosion- or wear-resistant alloy — think Inconel, Hastelloy, or stainless steel — onto a cheaper structural base. The result: a component that performs like it's made of expensive alloy, without the price tag of solid exotic material throughout.
This guide covers what clad welding actually is, how it's performed, where it differs from "cladding" in the broader sense, which materials and techniques fit which job, and how to vet a provider qualified to do it right.
Key Takeaways
- Clad welding metallurgically bonds dissimilar metals, adding parts corrosion or wear resistance without solid-alloy cost
- "Cladding" and "weld overlay" are often used interchangeably, but cladding also covers roll and explosion bonding
- Dilution control makes or breaks the layer: excess base-metal mix ruins cladding chemistry
- Flight-critical and process-critical work runs under codes like ASME Section IX and AWS D17.1, not guesswork
What Is Clad Welding?
Clad welding — often called weld overlay in this context — is a fusion welding process that deposits a metallurgically bonded layer of dissimilar metal onto a base material. The goal is corrosion resistance, wear resistance, or heat resistance, depending on the service environment.
The economics are straightforward: build the structural body from an affordable steel, then apply a thin layer of corrosion-resistant alloy exactly where it's needed. Sulzer's automated weld overlay guidance describes this as a permanent metallurgical bond that extends vessel life and avoids full replacement capital costs.
Solid-alloy fabrication works too, but for large components it can mean paying exotic-alloy prices for material that's doing structural work, not corrosion work.
The Dilution Problem
When you weld a cladding alloy onto a base metal, some of the base metal melts and mixes into the deposit. That's dilution. Too much of it, and the cladding loses the very properties you welded it on for.
There's no universal magic number here — it depends on alloy, process, and service environment. TWI's research on Alloy 625 overlays found corrosion resistance dropped sharply once iron dilution passed roughly 36% in a chloride test environment, while dilution itself ranged from under 5% to over 70% depending on process choice.
Typical dilution targets by process:
- Laser cladding: commonly 3–5%
- GMAW and GTAW: often 30–40%
Bottom line: dilution control determines whether your cladding actually protects the part.
Why Qualification Matters
Flight-critical and process-critical cladding work isn't something you hand to just anyone. It requires qualified welders and documented procedures under codes like ASME Section IX and AWS D17.1. At Alloy Metalworks, that means ISO 9001-controlled procedures on alloys such as Inconel 600, 617, and 625, Hastelloy, and stainless 316 and 347, with full documentation for audit and inspection.
How Is Clad Welding Performed?
Clad welding follows a controlled sequence. Skip a step, and you risk disbonding or cracking later.
- Surface preparation. Abrasive blasting removes contaminants and mill scale. EPRI's overlay guidance specifies grit-blasting to a "white metal" finish before any deposition begins.
- Method selection. Choice depends on thickness, alloy, and geometry:
- SAW for high deposition rates on thick layers
- GMAW/GTAW for controlled, moderate-thickness work
- Laser cladding or TIG hot-wire for precision, low-heat applications
- Controlled deposition. Heat input must be controlled carefully. On alloys like Inconel 617, too much heat risks distortion and metallurgical compromise; too little sacrifices fusion. In Alloy Metalworks' shop experience, an ultra-high-frequency pulse setup kept the arc stiff and focused at low heat input, improving bead consistency on this alloy.
- Post-weld heat treatment and inspection. Ultrasonic and liquid-penetrant testing verify bond integrity, and destructive coupon testing confirms the weld meets code.
For aerospace and research-grade parts, the process continues past the weld itself: documentation, material traceability, and inspection-ready reporting that compliance-driven programs require.
Cladding vs. Weld Overlay: What's the Difference?
Cladding is the umbrella term. It covers any method of bonding a dissimilar metal layer onto a base — fusion welding, roll bonding, explosion bonding, or powder metallurgy. Weld overlay, strictly speaking, refers only to the fusion-welded route.
In practice, most people in the shop use "cladding" and "overlay" interchangeably. That's fine day-to-day, but the distinction matters when specs get written:
- Cladding is often applied to semi-finished stock before final fabrication
- Overlay is typically applied to a finished component, often as a repair or final protective step
If a spec calls out "cladding" without qualification, ask whether they mean the welded version or something else entirely — it changes the process and the qualification requirements.
Common Materials and Techniques Compared
Materials and What They're Chosen For
| Material | Why it's selected |
|---|---|
| Inconel 625 | Strength, fabricability, and resistance to pitting, crevice corrosion, and chloride stress cracking |
| Hastelloy C-276 | Resists oxidizing and non-oxidizing acids, plus chloride pitting |
| Incoloy 825 | Nickel and copper content resist reducing acids and chloride stress cracking |
| Stainless steel (316, 347) | Molybdenum content improves general and chloride-pitting resistance |
| Titanium (Gr2, Gr7) | Excellent corrosion resistance, but oxygen-sensitive during welding |
Matching Process to Job
- SAW: High deposition (Miller reports rates up to 40 lb/hr); best for thick layers on large flat or rotating parts
- GMAW/GTAW: Moderate deposition with strong control; the workhorse for most moderate-thickness overlay work
- Laser/TIG hot-wire cladding: Minimal heat input for precision work; Lincoln Electric reports 5–10% dilution versus about 30% for standard GMAW/GTAW
Nickel alloys and titanium both need tightly controlled shielding. Titanium welded to AWS D17.1 Class A standards requires precise shielding-gas flow, tungsten stick-out, and travel speed. Weak coverage at the trailing edge or joint backside introduces contamination fast.
A dedicated purge setup or inert-gas chamber, rather than a standard torch shield alone, is often what separates a passing coupon from a rejected one on this work.
What Is an Overlap in Welding?
Overlap is a weld discontinuity, not a design feature. It happens when filler metal flows over the base metal surface without achieving proper fusion. The bead looks connected, but underneath, it isn't bonded. In cladding work, this is a real quality risk. An overlap defect can leave a gap where contaminants collect, and the protective layer above it isn't actually anchored to the base metal the way it needs to be. These defects are what procedure-qualification checks are built to catch:
- Visual inspection
- Liquid-penetrant testing
- Destructive coupon testing NDT isn't optional on cladding work, even when the surface looks fine.
Industries and Applications
Clad welding shows up wherever a component has to survive an environment that would eat through ordinary carbon steel.
- Aerospace and flight-critical hardware: Corrosion- and wear-resistant overlays on ground support equipment and structural components, often built to AWS D17.1 Class A requirements.
- Hydrogen, fuel cell, and clean energy systems: Cladding protects components exposed to extreme thermal and chemical cycling as hydrogen infrastructure scales up.
- Sanitary, pharma, and food processing: Stainless overlays built to AWS D18.1 and 3-A sanitary criteria for food-contact tube and pipe systems.
- Chemical processing and research equipment: Custom, small-batch cladding for reactors and lab-scale systems where standard stock doesn't fit.
Alloy Metalworks, based in Colorado, supports these exact sectors. TDA Research, for instance, brought the company in for major reactor modifications, completed early and under budget.
That work depends on engineering-aware fabrication and documented traceability from design through the finished part, backed by ASME Section IX and AWS D17.1 Class A qualification.
Frequently Asked Questions
What is clad welding?
Clad welding is a fusion welding process that bonds a corrosion- or wear-resistant metal layer onto a base metal. The bond is metallurgical, not mechanical, meaning it becomes part of the base structure itself.
What is the purpose of cladding in welding?
Cladding lets you use a cheaper structural metal for the body of a component while placing an expensive corrosion- or wear-resistant alloy only where it's needed. It's a way to get exotic-alloy protection without exotic-alloy costs throughout the part.
How is clad welding performed?
The process runs through surface preparation, method selection based on thickness and alloy, controlled deposition to manage dilution, and post-weld inspection. Each step protects against cracking, distortion, or disbonding later.
What is the difference between cladding and weld overlay?
Cladding is the broad category, covering fusion welding as well as roll bonding, explosion bonding, and powder metallurgy. Weld overlay refers specifically to the fusion-welded deposition method.
What is a weld overlay?
A weld overlay is the fusion-welded layer applied to a finished component, usually to protect against corrosion or wear, or to repair a worn surface. It's typically the final step in fabrication rather than something done on raw stock.
What is an overlap in welding?
Overlap is a weld defect where filler metal flows over the base metal surface without fusing to it. It's distinct from an intentional cladding layer because there's no real metallurgical bond underneath.
