Cladding welding (or weld overlay) is the industrial equivalent of giving a tank a suit of armor. It is a surfacing process where a layer of high-quality, corrosion-resistant metal is applied to a standard base material. The goal? To improve the surface properties of cheap, strong steel by coating it with a superior alloy like Stainless Steel or Inconel.
Think of it like gold-plating jewelry. You get the expensive look and resistance on the outside, but the core is a stronger, cheaper metal. In this guide, we break down the process, methods, and benefits of cladding for modern fabrication.
Key Takeaways
- Definition: Cladding welding applies a layer of corrosion-resistant metal over a cheaper base metal.
- Purpose: It combines the strength of steel with the surface protection of expensive alloys like Inconel or Stainless Steel.
- Difference: Unlike hardfacing (which fights wear), cladding primarily fights corrosion and heat.
- Methods: Common processes include MIG, TIG, Laser, and Plasma Transferred Arc (PTA).
- Technique: Success depends on controlling "dilution" so the base metal does not ruin the alloy layer.
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Gear: You need precise heat control, often achieved with ArcCaptain Synergic MIG Welders.
What is Cladding Welding?
At its core, cladding is about surface engineering. You are taking a component that is structurally sound but chemically vulnerable and giving it a shield.
When you weld a clad part, you are creating a metallurgical bond. This is very different from painting or thermal spraying. In painting, the layer just sticks to the surface. In cladding, the two metals fuse together.
They become one piece. This means the cladding layer will not peel, crack, or separate, even under high pressure or extreme temperature changes.
This process is vital for industries that deal with "sour" environments. That implies environments with lots of acid, salt, or sulfur that eat through standard steel in days.
Cladding vs. Hardfacing
These two look identical under the welding hood, but their missions are opposite. Confusing them can lead to catastrophic failure.
| Feature |
Cladding Welding |
Hardfacing |
| Primary Goal |
Corrosion Resistance (Rust/Acid) |
Wear Resistance (Impact/Abrasion) |
| Materials |
Stainless Steel (300 series), Inconel, Monel |
Tungsten Carbide, Stellite, Chrome Carbide |
| Properties |
Soft & Ductile (Bendable) |
Extremely Hard & Brittle (Rockwell C 50+) |
Why Use Cladding Welding? (The Benefits)
Why go through the trouble of welding a new surface onto a part? It usually comes down to cost and performance. Here is why engineers love this process.
1. Massive Cost Savings
Solid stainless steel or Inconel is incredibly expensive. Carbon steel vs stainless steel pricing shows that carbon steel is much cheaper. Imagine you need a pipe wall that is 1 inch thick.
- Option A: Buy a solid 1-inch thick Inconel pipe. This could cost $50,000.
- Option B: Buy a cheap carbon steel pipe and clad the inside with 1/8 inch of Inconel.
This creates the exact same corrosion resistance on the inside but might only cost $15,000.
2. Structural Strength
Exotic alloys are great at stopping rust, but they are not always the strongest structural materials. Some are too soft, while others are brittle. Carbon steel is excellent for handling pressure and weight.
Cladding gives you the best of both worlds. You get the backbone of steel and the skin of a super-alloy.
3. Repair and Refurbishment
Instead of throwing away a corroded valve or shaft, you can fix it. You can machine down the damaged surface and build it back up with cladding.
This restores the part to "better than new" condition because the new surface is often higher quality than the original.
The Science of "Dilution"
Before we talk about how to weld, you need to understand dilution. This is the most critical concept in cladding.
Dilution is the percentage of the base metal that melts and mixes into your weld puddle.
- High Dilution (Bad for Cladding): If you melt too much of the carbon steel base, it mixes with your stainless steel wire. This creates a mixture that is neither true steel nor true stainless. It will likely rust.
- Low Dilution (Good for Cladding): You want to melt just enough of the base metal to get a bond, but not enough to pollute your alloy layer.
For most corrosion-resistant applications, you want to keep dilution below 10% or 15%. This is why selecting the right welding process and settings is so important.
Common Cladding Welding Processes
There is no single "right" way to do it. The best method depends on your budget, the part shape, and the equipment you have.
1. GMAW (MIG Welding)
Using a MIG welder is one of the most common ways to clad a surface in smaller shops. It is fast and relatively easy to learn.
- Pros: High deposition rate (you put down a lot of metal fast).
- Cons: Standard MIG has high heat input, which causes high dilution.
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The Fix: Modern Pulse MIG or Synergic MIG machines solve this. They pulse the current to let the puddle cool slightly between droplets. This reduces how deep the weld digs, keeping the chemical purity high.
Equipment Tip: For consistent overlays, a machine with Synergic settings is a lifesaver. Check out our Synergic MIG Welders to get that precise control.
2. GTAW (TIG Welding)
For small repairs, valve seats, or high-precision work, manual TIG welding is king.
- Pros: Extremely clean welds with very precise control over dilution.
- Cons: It is very slow. Cladding a large pipe with TIG would take forever.
3. Plasma Transferred Arc (PTA)
This is a high-tech method often used for automation. Plasma Transferred Arc uses a focused plasma stream to melt metal powder onto the surface.
- Pros: It creates a very smooth layer with extremely low dilution (often under 5%).
- Cons: The equipment is expensive and usually automated (robots). You won't find this in a typical home garage.
4. Laser Cladding
This uses a high-power laser beam to melt the cladding material.
- Pros: Lowest heat input of any process. It causes almost no warping of the part.
- Cons: Very high equipment cost.
5. Submerged Arc Welding (SAW)
Used for massive industrial jobs, like cladding the inside of a reactor vessel. A blanket of flux covers the arc.
- Pros: Huge deposition rates using wide "strip" electrodes (looks like a tape measure).
- Cons: Can only be done in the flat position.
Step-by-Step Guide: How to Perform Cladding Welding
If you have a MIG or TIG welder and want to try cladding a part, here is the procedure.
Step 1: Surface Preparation
This is non-negotiable. You cannot clad over rust, oil, or paint.
- Grind the surface until you see shiny, bright metal.
- Degrease the area with acetone. Any oil left behind will boil out and cause porosity (bubbles) in your weld.
Step 2: Choosing Your Filler Metal
You usually need to use a "buffer layer" or a specific over-alloyed wire.
- Example: If welding 304 Stainless onto Carbon Steel, do not use 308L wire. Use 309L. The 309L has extra chrome and nickel to handle the dilution from the carbon steel.
Step 3: Setting Your Machine
You want a smooth arc with minimal digging.
- Amperage: Keep it on the lower side of the range for your wire diameter.
- Voltage: Keep it steady.
- Travel Speed: Move relatively fast. If you move too slow, the heat builds up and you melt too much base metal (high dilution).
Step 4: The Overlap Technique
You cannot just run beads next to each other randomly. You need a pattern.
- Run your first bead.
- Position your second bead so it overlaps the first one by about 50%.
- This overlap ensures you don't have low spots between beads where the protective layer is thin.
- Continue this pattern until the whole surface is covered.
Step 5: Multi-Layer Approach
For critical applications, one layer is rarely enough. The first layer will always have some iron mixed in from the steel base.
- Layer 1: The "Butter" layer. This mixes with the base metal.
- Layer 2: The "Cap" layer. You weld this on top of Layer 1. Since you are welding stainless onto stainless now, this top layer will be pure and fully corrosion-resistant.
Common Problems and Troubleshooting
Cladding is tricky. Here are the issues you might run into.
1. Underbead Cracking
Because you are welding two different metals, they expand and contract at different rates. This stress can cause cracks underneath the weld.
- Solution: Preheat the part. Heating the carbon steel to 200°F or 300°F before welding slows down the cooling process and reduces stress.
2. Porosity
Small holes in the weld surface.
- Solution: This is usually dirt or a lack of gas coverage. Clean your metal and check your gas flow.
3. Delamination
The clad layer peels off.
- Solution: This means you didn't get fusion. You likely ran too cold. Turn up the amps slightly or slow down just a bit to ensure the base metal is actually melting.
Safety Considerations for Cladding
Cladding is different from normal welding because you are doing it continuously for a long time. The heat accumulation is massive.
💥 Radiant Heat: Since you are covering a large surface area, the part gets extremely hot. It turns into a giant radiator. This can burn you through thin clothing.
✨ Tip: Use proper PPE. Standard cotton shirts might not cut it for long-duration overlay work. Ensure you have heavy-duty welding protective gear.
💥 Fumes (Hexavalent Chromium): When you weld stainless steel, dangerous fumes are released.
✨ Tip: Always use a fume extractor or a respirator.
💥 Spatter: MIG cladding can be messy.
✨ Tip: Protect your workspace. Spatter can fly everywhere during GMAW cladding. Use a fiberglass welding blanket to cover expensive machinery nearby.
💥 Fire Risk: If you are working on-site, the heat can linger for hours.
✨ Tip: Always keep a fireproof blanket handy to catch sparks and cover the hot part when you are done.
Conclusion
Cladding welding is the ultimate upgrade for metal parts. It allows you to combine the strength of cheap steel with the chemical resistance of expensive alloys. Whether you are repairing a worn shaft or building a pressure vessel, understanding this process adds a valuable skill to your fabrication arsenal.
It is a step up from standard joining. It requires you to think about chemistry, dilution, and heat input. But once you master it, you can tackle high-value projects that other welders can't touch.
Key Points to Remember:
- Cladding protects against corrosion, while hardfacing protects against wear.
- Dilution control is the most critical part of the process to ensure your stainless layer stays stainless.
- Safety gear is essential due to the high heat involved in surfacing.
Ready to start surfacing? Make sure your shop is equipped with the right machines and safety gear to handle the heat.
FAQs About Cladding Welding
Here are the questions we see most often from welders and fabricators.
What is the difference between overlay and cladding?
They are often used interchangeably. However, "overlay" is a general term that includes both hardfacing and cladding. "Cladding" specifically refers to corrosion resistance.
Can you clad with any metal?
Not exactly. The cladding material and the base metal must be compatible. If they are too different, they will form brittle phases and crack. However, almost all carbon steels can be clad with stainless steel or nickel alloys using the right filler wire.
Is cladding the same as coating?
No. A coating (like paint, powder coat, or galvanizing) is a physical bond. It sits on top. If you scratch it, it peels. Cladding welding creates a metallurgical bond. The two metals are fused together. You cannot peel the cladding off.
Do I need a special welder for this?
You can do it with a standard welder, but machines with Pulse or Synergic features make it much easier to control dilution. If you are doing this professionally, those features pay for themselves quickly.
