Can Laser Cladding Replace Traditional Overlay Welding in Chemical Equipment?

In chemical equipment, laser cladding can replace some conventional overlay welding processes, but it cannot completely replace them.High-end, critical, thin-walled, and distortion-sensitive components are likely to increasingly adopt laser cladding, while conventional overlay welding will remain the main choice for ordinary thick-walled, large-sized components and conventional operating conditions.

1. What Overlay Welding Processes Are Commonly Used in Chemical Equipment?

The most common processes include:

• Plasma transferred arc (PTA) cladding
• Arc overlay welding, including TIG welding, welding electrodes, and flux-cored wires
• Submerged arc overlay welding
• Strip cladding, commonly used for large-area cladding on vessel internal surfaces, towers, and heads

These are the main conventional overlay welding processes that laser cladding may replace in certain applications.

2. Where Can Laser Cladding Replace or Even Outperform Conventional Overlay Welding?

1) Valve Sealing Surfaces, Discs, and Seats

Conventional process: Stellite® plasma cladding.

Advantages of laser cladding include:

• Very low dilution, typically below 3–5%
• Better retention of the original alloy composition
• Small heat-affected zone and low distortion
• Smooth cladding surface
• Smaller machining allowance

As a result, laser cladding is increasingly being used as an alternative to PTA cladding for high-end chemical valves and hydrogenation valves.

2) Small, Thin-Walled, and Distortion-Sensitive Components

Typical examples include:

• Heat exchanger nozzles and small flanges
• Thin-walled liners and internal lining components
• Precision internal bores and small end faces

Conventional overlay welding can easily cause deformation, ovality, or dimensional changes in these components.

Because laser cladding introduces a relatively small amount of heat into the workpiece, it can significantly reduce thermal deformation.

This is one of the areas where laser cladding has a particularly strong advantage and can potentially replace conventional overlay welding.

3) Localized Corrosion- and Wear-Resistant Areas

Laser cladding can be used to reinforce specific areas such as:

• Local erosion zones
• Small sealing surfaces
• Shafts and shaft ends
• End faces of agitator blades

These applications do not require a large cladding area. Instead, only a localized area needs high-performance surface protection.

In such cases, laser cladding can be more economical and provide more consistent performance than conventional overlay welding.

4) Remanufacturing, Repair, and Restoration

Typical applications include:

• Pump shafts
• Valve stems
• Worn sealing surfaces
• Corrosion pits

Conventional repair welding can result in relatively high heat input, deformation, cracking, or uneven hardness.

Laser cladding provides a smaller heat-affected zone and allows the cladding thickness to be controlled more precisely, making it attractive for repair and remanufacturing applications.

This is already one of the major application areas where laser cladding can replace conventional repair welding.

3. Where Can Laser Cladding Not Yet Replace Conventional Overlay Welding?

1) Large-Area Cladding on the Internal Surfaces of Large Vessels

Typical applications include:

• Towers
• Reactor internal surfaces
• Large heads and shell sections
• Large-area cladding of 304, 316L, Incoloy 825, Alloy 59, and other materials

Conventional processes such as strip cladding and submerged arc overlay welding remain widely used.

They offer:

• High deposition rates
• Relatively low cost
• Mature and stable processes
• Well-established inspection and quality-control systems

Laser cladding currently faces challenges in these applications because of its relatively low deposition rate, higher equipment cost, and the difficulty of controlling flatness and overlap over very large surfaces.

Therefore, it is unlikely to completely replace conventional processes for large-area cladding in the short term.

2) Thick Cladding Layers

Chemical equipment may require relatively thick overlay layers, sometimes 3–5 mm or even thicker, particularly when high corrosion resistance or resistance to high-temperature hydrogen attack and stress corrosion is required.

Conventional multi-layer overlay welding is already a mature and reliable technology with well-established inspection procedures.

Producing thick layers with laser cladding can involve:

• Lower productivity
• Higher residual stress and cracking risks
• Higher processing costs

Therefore, conventional overlay welding remains the primary choice for many thick-layer cladding applications.

3) On-Site Construction and Field Repair

Examples include:

• Overlay welding at construction sites
• Repair work inside operating plants
• Large equipment that cannot be transported into a workshop

Laser cladding equipment can be more complex to deploy and may require better control of factors such as dust, temperature, and optical-path stability.

Conventional welding equipment, by comparison, is relatively easy to transport and set up on site.

Therefore, laser cladding cannot currently completely replace conventional overlay welding for many field applications.

4) Cost-Sensitive and Conventional Applications

For ordinary stainless steel overlay welding and non-critical components, conventional processes are already relatively inexpensive and mature.

In these applications, laser cladding may not offer a sufficient economic advantage to justify the higher equipment and process-development costs.

4. What About Corrosion Resistance, Standards, and Certification?

For chemical equipment, performance requirements often focus on issues such as:

• Intergranular corrosion
• Pitting corrosion
• Stress corrosion cracking
• Intergranular corrosion testing
• Ferrite control
• Non-destructive testing (NDT)

From a technical perspective, laser cladding can achieve corrosion and wear resistance that is comparable to or, under properly developed conditions, better than conventional overlay welding.

However, there are still practical challenges.

Compared with conventional overlay welding:

• Industry standards for laser cladding are less mature
• Customer and third-party inspection acceptance may require additional validation
• WPS, PQR, and acceptance criteria are not yet as mature as those for established strip cladding processes

Therefore, for existing projects and conventional applications, conventional overlay welding may still be the more straightforward and established choice.

For new projects, demanding operating conditions, and applications requiring an alternative to imported technologies, laser cladding can be considered.

Laser Cladding vs. Conventional Overlay Welding: Where Does Each Fit?

In chemical equipment, laser cladding can already provide a stable alternative to conventional overlay welding for localized, precision, thin-walled, distortion-sensitive, sealing-surface, repair, and remanufacturing applications.

However, for large-area cladding, thick overlay layers, large vessel internal surfaces, and field construction or repair, conventional overlay welding remains the dominant technology and is likely to remain so for a considerable period of time.

One important point: laser welding is not currently included among the welding processes listed in NBT 47014. Therefore, when laser cladding is considered for chemical equipment, technical feasibility alone is not enough; applicable standards, qualification procedures, customer requirements, inspection requirements, and project acceptance criteria must also be evaluated