African Fusion November 2020

TSASA: Laser cladding v thermal spray

Laser cladding versus thermal spray Which method is best for you?

meaning the area of the basemetal that has had its properties changed due to high temperatures. Laser cladding typically has a heat affected zone of around 0.75 mm thick (0.03″). This is highly beneficial if the part is prone to heat distortion. • One-step build-up process: Laser cladding also allows for thicker build up on a single pass compared to other processes. Overlapping passes meld together to produce a quality surface. This combined with lowmetal dilution, means there is minimal post-process machining. Laser cladding also has disadvantages, however: • Process limitations: Laser cladding is usually a robotically controlled process. While this creates greater precision, it is also less versatile. Not only is the system not portable, it can create complication for larger parts. • Material limitations: Laser cladding is typically only applied to a fewmaterials such as nickel- and cobalt-based alloys such as Inconel®, Hastelloy® and Stel- lite®, along with some stainless steels, suchas 300and400 series, andcarbides, such as tungsten carbide. These are great for wear and corrosion resistance but can fall short if you require other coating properties. • Coating thickness issues: Like most advantages, thick build up also has its downside. Since laser cladding lays

This article, from HTS Coatings of Illinois in the US and circulated in South Africa by the Thermal Spray Associa- tion of South Africa (TSASA), compares the advantages and disadvantages of laser cladding and thermal spray coating processes andmakes some simple suggestions for choosing between them.

W e live in the information age; one can find the answer to almost any question in minutes. Doing a simple internet search for ‘machine part repair’ or ‘remanufacture’ will result in thousands of ways andprocesses to rebuild parts and get themworking again. The hard part is figuring out which advice to take and who to trust. The even harder part comes when there are multiple kinds of repair processes that seem, at first glance, to do the same job. For thosewhohave everwonderedwhat the difference is between laser cladding and thermal spray and which one is right for you, you’ve landed in the right spot. Same but different In the broad scheme of things, laser clad- ding and thermal spray accomplish the same goal. They can be used to add a hard- ened, new surface to previously damaged or worn industrial components. They can be used for remanufacturing a component and even to better prevent future wear. Most people look to laser cladding due to its metallurgical bond but there are

thermal spray processes that can achieve this as well. So, which one should one choose? Let’s break it down and look at the processes individually. Laser cladding Laser cladding is a hardfacing process that uses laser energy tomelt andweld powder material to a surface. The result is similar to hardfacewelding but operates at amuch lower temperature; around 550 °C (1 000 °F) as opposed to over 6 000 °C (11 000 °F) for TIG welding. It forms a metallurgical bond with the substrate material and produces a hard, wear resistant coating. Laser cladding advantages include: • Metallurgical bond: The biggest ad- vantage to laser cladding is the metal- lurgical bond achieved at relatively low temperatures. Since laser cladding uses metallurgical bonding, there is little to no porosity in the coatings, resulting in fantastic long-termcorrosion resistance. • Lower Temperature: Laser cladding achieves this metallurgical bond at a lower temperature than most proce- dures. It has a small heat affected zone;

A summary of the differences between mechanical and metallurgically bonded coatings.

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November 2020

AFRICAN FUSION