Introduction to Thermal Spray Coatings

Oerlikon Metco

Thermal spray is an industrial coating process consisting of a heat source and a material feedstock - either in powder or wire form - that results in a surface modifying coating. Typically applied to metal surfaces, thermal sprayed coatings impart desired properties to these surfaces that result in a wide range of component improvements. In this way, the component can be rebuilt if worn or damaged, or a wide variety of qualities can be given to the surface, depending on the material to be used.

Thermal sprayed coatings have solved an extensive assortment of design and service problems encountered in our technological world. Today, in fact, you cannot fly in a commercial jet, ride in your automobile or put a shirt on your back without the benefit of a thermally applied coating that has either helped a component or system function better, or made the manufacture of an item possible or more economical.

By giving your product the advantages of a thermal sprayed surface, you can achieve advantages over your competitors. These include:

  • Reducing product costs
  • Solving problems such wear, corrosion, thermal effects, conductivity, and oxidation
  • Prolonging your product’s life
  • Reducing maintenance costs on your products or extending the time between maintenance and replacement
  • Giving your customers greater product satisfaction


Here is how Oerlikon Metco’s thermal coating technology can help you solve different physical problems that might affect your product.

Wear Resistance

The single most common use for thermal spray technology is to retard and control wear. Mastering the wear process means controlling a complex set of system variables that start with the physical characteristics of mating surfaces.

Wear challenges include the geometry and environmental aspects of a contact, the state of stress and stress distribution, the dynamics of motion, the quality of lubrication, the presence of contaminants, and the finish of the surfaces themselves. While several different wear phenomena — such as abrasive wear, adhesive wear, fretting or sliding wear — can act on the surfaces at once, they have a common result: Surface material is lost, ultimately causing a functionally significant change in dimension and impaired performance.

Oerlikon Metco thermal coating solutions are used to alter the hardness and finish characteristics of countless mating surfaces, to minimize the effects of mechanical wear, and extend product life. Thus, maintenance and operational costs are reduced in a world of applications.

Dimensional Restoration and Control

While you can delay the effects of wear, you can't stop it forever. Parts eventually lose dimensionality and must be replaced or resurfaced using thermal spray coatings. The ability to apply engineered coatings across a broad spectrum of thickness, finish and composition requirements makes thermal spray an ideal way to protect components from being discarded prematurely.

In a wide range of industrial applications, thermal coatings are being used to renew components by restoring their specified dimensions, and by matching, or sometimes improving, their original performance.

Certain applications call for controlling wear. Generally, these involve the need to achieve tight, nearly zero-clearance seals to increase the efficiency of mechanical systems with high-speed, rotating components. Because of the severe environments in which these coatings must operate, each must be designed to retain dimensional stability across a specific range of operating conditions.

Oerlikon Metco clearance control solutions provide appropriate thermal expansion, compatibility with mating surfaces and high-temperature corrosion resistance. Oerlikon Metco develops such "sacrificial surfaces" to meet a very broad range of operating specifications.

In addition to that, erosion-resistant abradable coatings developed by Oerlikon Metco provide a high-quality, cost-effective means for maintaining tight tolerances in the fan, compressor and turbine sections of gas turbine engines.

Corrosion and Erosion Resistance

Resisting environmental wear once meant enduring the elements of nature. Unfortunately, the environment today is no longer entirely natural. Gaseous and particulate pollutants have added significantly to a list of corrosive agents to which structures and equipment are exposed. These systems operate in environments we have never challenged before — from oil rigs in the stormy North Sea to submerged cables that run beneath it.

Oerlikon Metco has developed coatings to resist the effects of corrosion in virtually every operating environment in the world, such as bridges and steel structures.

The effect of fluids on a solid surface is due to the complex interplay of chemical action and physical forces. Direct exposure to liquids, gases, and particulate solids can produce chemical corrosion or erosion. The high-speed movement of these corrosive fluids prevents the formation of any protective oxide that might have formed in a static environment, thus subjecting the surface to erosion. Cavitation occurs when pressure changes in the liquid can lead to the formation and collapse of vapor bubbles. This produces high-pressure shock waves that can destroy metallic surfaces. Particles within the fluid can impact the surface, damaging it even further.

Emission control oxygen sensors need to operate in the hot gas flow of an automotive exhaust system. A porous Oerlikon Metco thermal coating protects the sensor while allowing the oxygen to pass through to the platinum electrodes.

High Temperature Operation

Technology creates thermal environments that challenge materials science. Exposure to these high temperatures can cause surfaces to lose functionality through oxidation or chemical attack. Oerlikon Metco coating solutions are used to add new surface properties to underlying technical substrates.

Those coating solutions improve heat transfer characteristics and help to retard the destructive effects of chemical and oxidizing agents. The ability to control the way materials respond to temperature extremes helps extend the life of mechanical components.

Electrical and Thermal Conductivity

Thermal sprayed coatings can exhibit excellent electrical characteristics. Such properties often differ significantly from those of the materials from which the coating was formed. Plasma sprayed copper, for example, demonstrates exceptional conductivity, so it's a perfect tool for producing highly efficient electrical connections. A thermal sprayed coating of aluminum has 20% greater conductance compared to wrought aluminum, making it ideal for the manufacture of heating elements. A coating of thermally sprayed alumina exhibits superior voltage break-down strengths, making it an ideal electrical insulator.

The parabolic surfaces of fiberglass up-link and down-link satellite antennas receive a thermal coating to create a cost-effective conductive surface. Lower cost is also the reason that coatings using Oerlikon Metco products have replaced conducting paints and foils for protecting satellite antennas from RF interference.

An Oerlikon Metco coating is used as an insulator in the casting and forging industry to prevent electrical continuity from being established between sections of high-pressure water piping.

The automotive industry applies one of Oerlikon Metco’s thermal spray coatings to distributor rotors in order to reduce electromagnetic interference and suppress noise.

Conclusion

Oerlikon Metco has had a long history of solving customer's design and service problems. Their extensive product line of coating materials and thermal coating processes allow them to offer customers the flexibility and variety needed to achieve their specific application and design goals. In addition, the technical staff brings to their customers all the experience and knowledge necessary to provide the right coating solution to do the job.

Contact Oerlikon Metco today to get more information.

Article by Oerlikon Metco

Oerlikon Metco enhances surfaces that bring benefits to customers through a uniquely broad range of surface technologies, equipment, materials, services, specialized machining services and components. The surface technologies such as Thermal Spray and Laser Cladding improve the performance and increase efficiency and reliability. Oerlikon Metco serves industries such as aviation, power generation, automotive, oil & gas, industrial and other specialized markets and operates a dynamically growing network of more than 50 sites in EMEA, Americas and Asia Pacific. Oerlikon Metco, together with Oerlikon Balzers, belongs to the Surface Solutions Segment of the Switzerland-based Oerlikon Group.