Hardfacing working steel rolls is a worthy investment in component lifetime, paying for itself by reducing the frequency of downtime resulting from worn down equipment.

Whether you are talking about calendaring rolls, spreading rolls, leveling rolls, drawing rolls or high temp rolls, working steel rolls are ubiquitous in many industries. Whether it be paper, textiles, or steel, many products we use every day were manufactured using working steel rolls of some type. These manufacturers all use working steel rolls to shape, form, strengthen and convey materials through the manufacturing process.

Over time, the surface of the rolls will degrade, leading to costly line down time or poor-quality manufactured materials. For this reason, steel rolls are expensive consumables in the manufacturing process. We see a variety of rolls issues, including changes in roll diameter and surface quality.

In many cases the lowest hanging fruit for reducing production costs associated with line downtime is the fast and efficient refurbishment of the steel rolls. There are three common methods used to repair working rolls which are plasma spray, HVOF and laser cladding.

Plasma Spraying – a process in which the material to be deposited (typically a powder, liquid, or wire) is introduced into a plasma jet emanating from a plasma torch. The material is melted to the order of 10,000 K and propelled towards a substrate. The molten material then rapidly solidifies leaving a deposit adhering to the substrate.

High Velocity Oxygen Fuel Spraying (HVOF) – a mixture of gaseous or liquid fuel and oxygen is fed into a combustion chamber where they are ignited and combusted continuously. The hot gases created by the process are at a pressure close to 1 MPa and emanated through a converging-diverging nozzle and travels through a straight section. The velocity at which the gasses exit the barrel can exceed the speed of sound. A powder feed stock is injected into the gas stream, accelerating the powder up to 800 m/s. The stream of hot gas and powder is directed towards a substrate where the powder then melts and is deposited onto the substrate. The result is a low porosity coating.

Laser Cladding (Laser Metal Deposition) – a method by which an engineered metal powder or wire feedstock is melted and consolidated using a laser to coat a substrate or fabricate a near-net shape part. The interaction of the engineered powder, laser and substrate produces a melt pool. As the laser moves across the substrate, it leaves a track of solid metal. This creates a metallurgical bond versus an applied coating.

Laser cladding could be the key to dramatically reducing downtime in these industries. By using lasers and engineered metal powders to resurface (also known as hard facing or hard surfacing) the diameter of the steel rolls, we can restore the diameters of the steel rolls to a like new or even better than new condition. Typically, the surface of a laser clad roll is harder and more resistant to corrosion and wear than a new unclad roll. This is due to the metallurgical bond that is created vs. a traditional coating. A metallurgical bond is the result of chemical bonding that occurs between a substrate and the engineered powder or wire feedstock. Laser cladding can obtain the best balance between the two materials being bonded together. This bond can be adjusted to enhance properties such as:

  • Hardness
  • Toughness
  • Strength
  • Performance in extreme temperatures
  • Fatigue
  • Corrosion resistance
  • Weight

If your production facility uses working steel rolls and is looking to dramatically increase the useful life of the rolls (up to 10x), in turn reducing downtime, then you should be looking into hardfacing with laser cladding technology. If you are ever in doubt of which process to use, just ask a trusted metallurgist whether a laser clad metallurgical bond is superior to a sprayed or applied coating. You will likely find that laser cladding will be the top choice to outperform the others by providing stronger, longer lasting equipment.