Thermal Spray Coating & PTA cladding services
Tel: +27 11 316 6520/8/9
Email: thermaspray@thermaspray.co.za
 

Plasma Coatings

Thermaspray has undertaken a strategic partnership with Plasma Coatings in the USA to offer the South African market a new range of surface technologies and coatings to tackle the food, printing and packaging, tyre and rubber, paper and pulp, fempro/diaper and many more industries. These coatings are designed to solve many of the above industries’ problems resulting in decreased maintenance, higher outputs, and an increase in cost savings

What are Plasma Coatings?

Plasma Coatings combines the benefits of conventional thermal spray coatings with polymer coatings.

They utilise hardfacing techniques, dispersion spray and electrostatic methods to apply coatings. Each process deposits a coating onto a prepared base material forming a mechanical bond that enhances the properties of the surface.

What makes plasma coatings unique is the application of a double layer consisting of a metallic/ceramic thermally sprayed bond coat providing adequate roughness and excellent wear resistance and a polymer top coat providing a coating with superior adhesion strength and release and traction properties. This results in a coating with a combination of the best properties of ceramics, metals, and polymers.

Below is a schematic of a plasma coating:

The double layer consists of:

1. Thermal Spray (Bond coat)

This is the method of applying materials onto a prepared base material by heating particles in the stream of a heat source, creating a semi-molten state.

The particles are then propelled by high velocity onto a prepared substrate where they adhere to the base surface via a mechanical bond.

Particles continue to build until a specified thickness is attained. This technique is considered the "cold method of welding", whereas high temperatures can be achieved in the heated pocket, the temperature of the part itself usually remains under 100°C.

Typical physical specifications of coatings:

  • Maximum hardness of 72 Rc hardness (Tungsten Carbides)
  • Surface texture as sprayed is rough, from 150 to 1000+ Ra
  • Thickness range from 50µm to 4mm
  • Bond strength range: 17MPa -100MPa

Advantages

  • No degrading of parts due to heat warping and distortion
  • No degrading of part metallurgy or integrity
  • Surfaces are enhanced to provide improved performance

The following five core bond coat application techniques are used:

  1. Combustion Wire Metallizing: In this process, various metal wire is fed into an oxygen-acetylene gas mixture. It is then in a molten state and sprayed onto the part being processed.
  2. Electric Arc: This process also uses materials in wire form, but in this case the heat source is the arcing of two electrically conductive wires. The material is melted and propelled onto the part at a greater velocity than seen in the metallizing process. Higher temperatures allow for an increased source of base materials, faster rates of deposition, and improved bond and coating density.
  3. Thermal Spray: Like metallizing, our thermal spray is based on an oxygen-acetylene heat source. Unlike metallizing, however, the material begins in powder form. This process provides a larger selection of base materials and better bonding and density.
  4. Plasma Spray: In this process we use various gasses that are ignited by an electric arc. Temperatures can rise up to 12000° K while the part temperature remains at less than 100°C. One of the benefits of using this system is the high heat, which can process materials with high melting points (including ceramics).
  5. HVOF (High Velocity Oxygen Fuel): In this process particles actually travel faster than the speed of sound, generating the best bond strengths, density and hardness of all our processes. HVOF does not reach temperatures that are attainable with plasma processes so materials such as ceramics cannot be processed with this technique at this time.

2. Polymer System (Top Coat)

A wide range of polymers are also available, typically in the 20µm -80µm thickness range. Methods of application will vary, as will the curing methods.

Through dispersion or electrostatic systems we apply:

  • Fluorocarbons
  • Fluoropolymers
  • Silicones
  • Epoxies
  • Teflon® industrial coating
  • The use of special polymers (PTFE, PFA, FEP etc.) provides surfaces that are both hydrophobic and oleophobic preventing various materials such as adhesives, rubber, synthetic materials or food ingredients from sticking. These non-stick properties can be further enhanced by increasing the substrate/coating roughness profiles and reducing surface contact area. 
  • As a result of an infusion process, polymers and fluoropolymer coatings have a very good mechanical bond to the substrate.
  • Polymer and fluropolymer coatings can be applied to any substrate including aluminium, steel, stainless steel, tool steel, copper, and ceramics etc.
  • These coatings are temperature resistant up to approximately 280°C and many are FDA compliant for direct food contact. 
Applications:

Corrosion protection

Wear and Abrasion resistance

Surface Traction coatings

Release (non-stick) & Cleanability

Low Friction coatings

Non Conductive & Conductive coatings

 

Industries Served:
  • Tyre and Rubber Industry
  • Paper and Pulp Industry
  • Food and Beverage Industry
  • Pharmaceutical Industry
  • Diaper / Fempro Industries
  • Tapes / Adhesives Industry

Benefits of Polymer Coatings:

  • Improved part performance
  • Improved machine efficiency
  • Improved cleanability
  • Improved quality
  • Improved safety
  • Machine hygiene issues
  • Tension control