WHAT IS THERMAL SPRAY
Thermal spray refers to a set of processes that utilize heat energy to produce coatings using feedstocks that include metals, cermets, ceramics and plastics. The feedstock is deposited in a molten or semi-molten state in layers and adheres to the work piece by mechanical means. The coating material may be in powder or wire form.
The CTS Thermal Spray Processes
Thermal spray as practiced by CTS includes four processes - combustion spray, plasma spray, arc spray and
HVOF spray. All of these processes produce coatings that are serviceable for various applications. The selection
of a process takes into consideration all the requirements of the application.
Combustion coatings are typically not as well bonded as coatings produced with other processes, but can often be applied in very thick coatings due to their low coating stress.
Plasma coatings are outstanding for ceramics and other high melting point materials.
Arc coatings are excellent for large areas or on site applications.
HVOF coatings are excellent for wear resistance or where very dense coatings are required - such as chemical corrosion applications.
Each of the processes has its place in applying thermal spray coatings.
The Steps of Thermal Spray Application
The typical thermal spray application consists of several basic steps:
- Degrease the part
- Mask off the areas where coating is not desired
- Grit blast to roughen the surface
- Spray the coating on
- Remove the masking
- Clean up the part
- Machine the coating if required
- Inspect the part to insure adherence to quality standards
All of these steps are necessary in most applications in order to produce a serviceable coating.
Application Examples
Many well known applications exist such as coatings of zinc or aluminum applied to bridge structures
in order to drastically reduce rusting and extend the structure's service life. There are many applications
designed to extend the service life of industrial machinery components such as molybdenum coatings on shifter forks
to improve lubricity and extend life or the use of zinc or aluminum coatings on gas bottles (such as acetylene
or oxygen bottles) to extend their service life by keeping them from rusting.
There are highly technical applications like thermal barriers utilizing complex alloys and high tech ceramics
and garden-variety applications using steels or stainless steels to build up worn areas.
Industry Examples
Thermal spray is well recognized as a tool for component performance enhancement in many industries including:
- aero and land based gas turbine
- steel and aluminum production
- automotive, infrastructure such as bridge and road building and maintenance
- chrome plating replacement
- heavy construction equipment petrochemical, pump and valve
CTS is strong participant in many of these markets.
Designing components with thermal spray
coatings as one of the features is a method for optimizing performance of machinery by the
original equipment manufacturer. For example, pump manufacturers often specify specialized coatings called self-fluxing alloys as a means to increase service life of components - especially pump sleeves. These coatings are applied using the combustion powder process and then the coating is melted onto the part. A diffusion layer is formed with the substrate and the coating becomes a part of the component. The coating is then ground to size and the component exhibits superior wear life as a result of the hard self-fluxing alloy overlay. CTS is expert at the application of these self-fluxing alloy coatings.
Land based gas turbine manufacturers design in thermal barrier protection to many of the components that are exposed to hot gasses, particle erosion and severe thermal cycling. Many other industries also use this method to insure maximum service life for their critical components and wear parts.
Thermal spray coatings can also be used to rebuild worn parts and can be used to make components better than new by analyzing the wear patterns and operating environment, then prescribing coatings to extend service life.
In addition to thermal spray coatings, CTS offers dry film lubricants and release coatings all of which can enhance the surface properties of our coatings or can sometimes improve the performance of components even without using thermal spray coatings.
It is important to note that coatings are applied selectively where they are needed and that they protect components from exposure to heat, chemicals, molten metal, abrasion, adhesive wear, galling, fretting, or something as simple as weathering. The limit to the applications that are possible is your imagination.
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