Advantages of laser cladding vs hardfacing weld overlay

Advantages of Laser Cladding vs PTA, TIG, MIG Hardfacing / Weld Overlay

Laser cladding and  PTA (Plasma Transferred Arc),TIG (Tungsten Inert Gas)  and MIG (Metal Inert Gas) are all surface coating methods in which either a powder or wire of cladding material is heated and melted, this is then deposited over a base material which results in formation of metallurgical bond between the coating and the base material. These surface treatment methods are used to repair worn out and damaged parts as well as giving protective coating to new components.These  coatings enhance the  wear, corrosion and abrasion resistance of the component thus increasing its working life and durability.

However, while comparing Laser cladding with above mentioned methods there are some crucial differences, let’s have a detailed look:

1. Lower Heat Input 

Of all the above methods for hardfacing Laser cladding has the lowest  heat input. This   has very significant advantages

• Since the heat going into the base material can be precisely controlled in lasers this results in very low dilution (typically <5%) into the base material. So one doesn’t have to deposit a very thick coating to overcome the problems caused by high dilution which happens in PTA,TIG and MIG.
• The Heat affected zone is very minimal in laser cladding. So the properties of substrate material just below the hardfacing layer are not significantly altered.
• Lower heat input results in minimal/nil  distortion hence cost of remachining due to distortion also goes down.
• Laser cladding can be done on thin walled components, knife edges and many more complex geometries because of the precise nature of the laser beam.
• Due to lower heat input  less stress is induced into the coated parts.

2. Choice of Materials that can be deposited

MIG welding being a wire based method is limited in the types of hardfacing coatings it can deposit. Most commonly used coatings such as Cobalt (Stellites), Nickel and Tungsten carbide based alloys can be deposited by laser cladding as well as PTA and TIG. Similarly stainless steel , some tool steels and martensitic steels can also be deposited by laser cladding. Also  Many exotic combinations such as Copper based alloys, Aluminum bronzes are possible to clad with lasers nowadays.

3. Superior Quality Coatings

Laser cladding can deposit fully dense, metallurgically bonded coating having very less/nil porosities and other defects. Due the precisely controlled heat input the properties of the powder material being deposited are also preserved

• For example:  In Nickel based Tungsten Carbide coatings the tungsten carbide particles don’t melt and maintain their shape and size and don’t sink to the bottom of cladding  hence giving superior performance.
• Due to faster cooling rate in laser cladding, harder coating with very fine microstructures can be deposited. For example, Stellite 6 deposited with laser cladding can result in hardness of 50-55 HRC whereas the coating deposited by PTA, TIG will have lower hardness.

4. Cost saving 

Most of the hardfacing powders such as Cobalt and Nickel based powder are costly. Since we don’t have to deposit a very thick layer to get the properties of the upper hardfacing layer, the consumption of powders is significantly reduced. Added to that  laser cladding is a robotized process hence consistent coating quality is easily obtained. Laser cladded parts last longer  due to the superior quality of coating. These advantages have made  laser cladding a very attractive solution for hardfacing/repair  of components in a range of industries such as Oil and gas, marine, mining, automotive components, power generation, aerospace to name a few.

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