Thermal Plasma Spray Coatings – The Engineer’s Choice for Parts that Need to Be Able to Withstand Extreme Service Conditions. The coating is chosen to protect the part against a variety of potential problems, which are determined by the engineers designing the part.
Extreme Heat
Thermal Plasma Spray coatings are used for high temperature applications and here a number of Ceramic coatings are applied to provide a high temperature surface. In particular Yttria-stabilised zirconia (YSZ) is a very common coating that is used for Turbine blades and for the surface of Combustion Chambers. This coating acts as a thermal barrier to reduce the surface temperature of the metal below the critical temperature for thermal failure.
Abrasive Wear
Hard wear surfaces such as tungsten carbide and chromium carbide coatings are designed to withstand grinding, abrasion, wear by friction and impact. These coatings are often used on items such as in mining, on the inside of pumps and on rollers to name a few. The dense coating provides an excellent wear surface which will last longer than most untreated metals.
Oxidation and Corrosion
Alumina and MCrAlY coatings are used to combat the effects of oxygen and other chemicals to protect equipment in a variety of environments such as petrochemical plants and marine. In these situations the surface of a component is likely to be exposed to moisture and possibly be subject to salt attack as well as being exposed to a variety of chemicals. In these situations an exposed surface of bare steel or aluminium is likely to be rapidly attacked by such a combination of influences.
Electrical Insulation
Alumina coatings can also be used as electrical insulators. These coatings have a high dielectric strength and are often used on rollers, mandrels and other components that are used in electrical equipment. Thermal Plasma Spray is covered in more detail at www.poeton.co.uk/surface-treatments/thermal-metal-sprays/plasma-coatings.
Chemical Attack
Ceramic coatings, that are sprayed using Thermal Plasma Spray, are dense and therefore provide a barrier to the attack of acids, alkalis and solvents on metal surfaces. In many cases, equipment such as chemical reactors, mixing tanks and process plants for the handling of chemicals are coated to prevent attack by chemicals. In many cases the cost of replacement of a component, should it fail, is so high that coating the component is economic.
Process Safety
Fumes and small particles are released during any spraying operation. These must be controlled to maintain safe levels of airborne exposure in accordance with the HSE’s ‘Workplace exposure limits for metalworking processes’.
The key to selecting Thermal Plasma Spray coatings is to identify the primary problem i.e. heat, wear or chemistry and then select the most appropriate material to provide the solution.