Plasma spray is a form of thermal spray coating. It is the process of spraying a molten or heat softened material onto a surface to form a coating. The coating material, in the form of a powder, is injected into a very high temperature plasma flame which then heats the powder and accelerates it to very high speeds. When the now molten coating material comes into contact with the substrate (surface of the material which is to be coated) it then rapidly cools, bonding to the surface to form a coating.

How does Plasma Spray coating work?

Plasma is the term used to describe a gas that has been heated to such high temperatures that it ionizes and becomes electrically charged. The plasma spray gun achieves this by utilising the combination of a copper anode and tungsten cathode inside the gun, around and through which a gas (usually either argon, nitrogen, hydrogen or helium) flows. This causes the gas to become plasma where it is then forced out through a constricting nozzle where it is mixed with the coating substance in powder form. The powder then becomes molten and is fired out of the gun towards the substrate where it then cools and forms a coating.

Top Uses

When carried out correctly the plasma spray coating process is known as a ‘cold process’, as even though the plasma stream itself is very hot, the actual temperature of the substrate material that is to be coated can be kept relatively cool. This means that damage, metallurgical changes and distortion to the substrate material can be avoided and so more delicate substrate materials can be successfully coated using this process. However the extreme heat of the plasma also means that materials with very high meting points, such as refractory metals e.g. tungsten and ceramics e.g. zirconia, can used as coating materials.

Advantages

There are a number of advantages including:

• Wide variety of materials that can both be coated and be used to form coatings.
• Higher quality coatings can be achieved compared to other types of thermal spray processes.
• A broad range of powder particle sizes can be used, typically between 5-100µm.
• Well known process that is widely available and well understood.

Disadvantages

Although this is a very popular type of thermal spray coating, plasma spray does still exhibit a number of disadvantages which include:

• The specialist equipment is expensive to buy at the outset.
• Due to the high temperatures involved the internal components of the guns experience rapid deterioration and so must be replaced at regular intervals.
• The high temperatures involved can result in carbide decomposition or excessive oxidation when spraying in air.

For more information about the suitability of plasma spray coatings for your project, contact the experts at IRS Ltd today.

Thermal spraying is the process by which a coating is applied to a material via the coating material being heated until it becomes molten and then being sprayed onto the substrate where it solidifies and bonds upon contact forming a stable and hard wearing coating. There are a number of advantages (along with some disadvantages) to thermal spray coatings which are detailed below. 

Advantages of Thermal Spray Coatings

• Wide range of coating materials – there is a vast array of different materials which can be turned into high quality coatings via the thermal spray process. These can include; metal, alloy, ceramic, plastic and polymer and can be in the form of powder, rod or wire. The coating material can be specifically selected for each individual substrate and the job that it has to do and so a near perfect match can often be made between the two.
• Wise variety of substrate materials – as long as the material to be coated can withstand the heat of the thermal spray process then almost any material can be coated using this method. However there are also a number of specific spray coating methods which in fact use much lower temperatures and so the range of substrate materials is even further increased.
• Extends the lifespan of the substrate – a strong and efficient thermal spray coating will extend the lifespan of that substrate by providing an effective barrier against erosion, decomposition and other forms of surface damage. Thermal spraying allows much thicker coatings to be applied (often up to 10mm) in higher deposition rates than other coating methods, which provide a much more effective barrier against wear and tear.
• Reduced cost – in many cases repairing an object by applying a thermal spray coating to it is much cheaper than completely replacing it. Also thermal spray coatings tend to be much more efficient and waste less of the coating material than with other methods so are a much more viable option when more expensive coating materials are involved.

Disadvantages of Thermal Spray Coatings

• Disguises the substrate – as thermal spray coatings are so efficient in many cases it is impossible to tell what material the substrate was made of after the coating process, unless stringent records are kept.
• Cannot precisely evaluate effectiveness – once the thermal spray coating has been applied it is often difficult to tell exactly how well the coating has gone on, other than by a visual assessment.
• Costly set up – some of the methods of thermal spray coatings require very expensive apparatus, which can result in a high initial set up cost.

To find out more about the thermal spray coating process and how it could be applied to your business or field contact the experts at IRS Ltd today.

Whether a dealer, a collector or the proud owner of a single precious vintage vehicle, you know exactly how hard it can be to keep them maintained and in the best condition. As time passes and your vintage car gets older and older, there will be elements of ageing that start to show and some parts may need replacing. The trouble with older vehicles is sourcing those parts and in many instances owners now look to find ways of prolonging the life of their vehicle, rather than starting the long and difficult search for a rage engine block or shift fork.

Thermal spray technology has been used in the automotive industry for many years. It is a standard process in the manufacturing and maintenance of many modern cars but thermal spray coatings could also be a great way of enhancing and prolonging the life of a vintage vehicle. The process involves improving the engineering function of the car through the spraying of a thermal coating which is designed to protect. Thermal spray coatings have been used in the automotive industry to improve electrical insulation and lubrication as well as prolong the life of elements of the car, through the prevention of wear, tear, scuffing and crucially for older vehicles, corrosion.

How can Thermal Spray Coatings be used for your Vintage Car?

There are many different applications of thermal spray coatings for vintage cars but you’ll commonly find the process used for shift forks, engine blocks, cylinder liners, turbochargers, con rods, synchronising rings and many other internal elements of your vehicle.

There are different kinds of thermal spray technology too which may be used for different purpose as follows:

Combustion Spraying

Also known as low velocity oxygen and fuel spraying involves the projection of molten material onto the surface to create the coating. The spray comes out in powder form and is fed through the centre of a flame and it is often used to spray surfaces which cannot be exposed to high temperatures. Combustion spraying is often used for repairs, efficiency enhancement and restoring the shape/dimensions of a surface or component.

Plasma Spraying

A highly energetic and efficient plasma jet sprays a melted and highly accelerated ‘coating’ of particles onto the surface. The heat source is generated by a high density arc current and pure metal coatings as well as alloys, carbides and ceramics can be sprayed this way. It is used commonly for corrosion resistance, oxidation resistance and protection against wear and tear.

Arc Wire Spraying

Using two electrically charged metallic wires, this type of thermal spraying involves the creation of an arc using these wires. The wires feed through a spray gun system and can reach temperatures in excess of 4000 degrees. This particular spraying method forms a very high bond strength between the coating and the surface and the coating is usually denser than a flame sprayed version.

Protecting and prolonging the life of your vintage vehicle is entirely possible with the right thermal spray technology.

One of the many reasons that people choose to utilise thermal spray processes is the reclamation and refurbishment of components that are worn or damaged and no longer viable in their current state. However rather than opting for an expensive replacement part, many components can be returned to a state even better than new when treated with one of the many thermal spray coating processes.

So what are thermal spray coatings?

Thermal spray coatings are the process by which one material (the substrate) has a coating applied to it (which can be made up of a number of different materials). This coating is applied by the process of heating the coating material up until it becomes molten and then spraying this onto the substrate. The coating material then solidifies upon impact with the substrate bonding with it on a molecular level and forming a very tough and durable coating.

How can this be used for component reclamation?

Wear and tear of components is a common side effect of many manufacturing (and other) processes. However often these components are expensive and/or difficult to replace. In these instances, many of these components can quickly and easily be returned to full working order by simply applying an strong, tough and durable thermal spray coating. Coatings can be applied to cover the entire component or in some cases may be applied to just the worn area.

In many cases worn or damaged components can actually be made better than their original state by the application of a thermal spray coating. For example, if the component is especially susceptible to wear it may be possible to coat it with a different material that is much stronger and more durable than the original. This would then result in the component lasting for longer and thus significantly reduced downtime for your business.

Even surprisingly delicate components can be reclaimed via the application of a thermal spray coating, as even though the name suggests that the coating is very hot, in some types of thermal spraying the substrate actually stays at an ambient temperature and so any metallurgical changes that could weaken the substrate if it was exposed to too high a heat is avoided.

To find out more about our expert component reclamation services, contact IRS Ltd today.

When it comes to extending the lifespan of machinery, structures or their composite parts many people’s minds will automatically point towards painting as a way of protecting these from corrosion or decay. However is this really the best answer? In many case applying a thermal spray coating can be a much more advantageous idea. The thermal spray coating process in its basic form is the process of heating one material until it is becomes a liquid and then spraying this onto the material to be coated (the substrate) where the molten material then solidifies to form a coating.

So what are some of the advantages of applying a thermal spray coating to a material instead of painting it?

Thermal Spray Coatings Last Longer

In many cases thermal spray coatings have a significantly longer lifespan than you can expect from a painted coating. Because thermal spray coatings can be made up of a variety of different materials; everything from metals and alloys to plastics and ceramics, the coating can be chosen to have the greatest corrosion resistance for the specific condition in which the coating material will be operating, whether that be outdoors or within a corrosive indoor environment.

Thermal Spray Coatings Are More Efficient

Compared to paint where up to 70% of the constituents of the paint itself are lost to evaporation, thermal spray coatings are much more efficient as they can be applied directly to the substrate with little or no wastage. Also in some forms of thermal spraying any over-spray can in fact be collected and reused, whereas this would be impossible with paint.

Thermal Spray Coating Contain No VOC’s

Paint is made up of the pigment itself mixed with numerous Volatile Organic Compounds (VOC’s), which as mentioned above can constitute up to 70% of the paint itself. Upon drying these VOC’s evaporate out of the paint and are released into the atmosphere where they can be extremely harmful to the environment.

Thermal Spray Coatings Cost Less In The Long Run

Although some thermal spray coatings may cost more to apply initially, they last much longer and so removal and reapplication is much more infrequent than with many painted surfaces. In some instances a pained surface could need to be sandblasted and stripped before being repainted within 5 years, whereas a thermally sprayed surface could last in excess of 30 years. The cost savings in both the repainting process itself and any associated downtime can be significant.

For more information about utilising the advantages of thermal spray coatings contact the experts at IRS Ltd today.

High Velocity Oxygen Fuel Thermal Spraying, or HVOF for short, is a thermal spray coating process which relies on a high velocity but low temperature procedure to create extremely dense and strong coatings.

How does HVOF spraying work?

During the HVOF spraying process particles of the coating material are sprayed at the substrate (the material which is to be coated) at supersonic speeds. The extreme kinetic energy of these particles allows them to bond with the substrate to form a very dense and strong coating. To achieve this result fuel and oxygen are sent into a combustion chamber under pressure and in a continuous flow, which produces a jet of combustion products at extremely high speed. The coating material, in the form of powder particles, is then injected into this gas stream and becomes accelerated towards the substrate at a very high velocity. There are a number of different types of HVOF spraying guns and processes which differ in the types of fuel that they use (hydrogen, natural gas or kerosene) and their oxygen source (pure oxygen or compressed air).

What materials is HVOF suitable for?

HVOF is most suitable for use creating thermal coatings on the following materials:

• Tungsten
• Chrome & Nickel Carbides
• Titanium
• Super-Alloy Ranges
• Hastelloy
• Inconel
• Monel
• Iron based alloys, AISI 316L, etc

Advantages of HVOF spraying

In general HVOF is thought to result in an improved coating quality compared to other thermal spraying processes. Advantages include:

• Higher density (lower porosity) coatings due to greater particle impact velocities.
• Lower cost compared to other thermal spray methods.
• Better wear resistance as a result of harder, tougher coatings due to less degradation of carbide phases.
• Relatively cool coating process, due to the brief presence of particles in the hot gas stream.
• Lower compressive stress which results in thicker coatings being able to be applied.
• Higher strength bond to the underlying substrate and improved cohesive strength within the coating.
• Lower oxide content due to less in-flight exposure time.
• Smoother as-sprayed surface due to higher impact velocities and smaller powder sizes.

Disadvantages of HVOF Spraying

• HVOF sprayed coatings can be extremely complex, due to the numerous variables within the method.
• Powder sizes are restricted to a range of about 5 – 60µm.
• HVOF spraying usually needs to be undertaken in a specialised workshop, with suitable sound attenuation and dust extraction facilities.
• Equipment costs are high initially.
• HVOF is not suitable for creating coatings on many internal, or other restricted access surfaces as HVOF spraying needs line of sight to the surface and a spray distance of 150-300 mm.

To find out more about the HVOF and other Thermal Spraying Systems options, contact the experts at IRS Ltd today.

Here at IRS Surfacing Technologies Ltd we are proud to be specialists in many different forms of surfacing technologies, just one of which being thermal spray systems. But what exactly is a thermal spray system (often called thermal spraying) and how could it be of use to you and your company or product?

What is thermal spraying?

In essence thermal spraying is a wonderfully simple concept and this is probably one of the reasons why it works so well. In its simplest form thermal spraying involves one material being heated until it is molten and then being sprayed onto another material to coat it. Obviously there is actually a lot more to it than that and there are several different types of thermal spraying, each of which is suited to its own specific applications, whether it be the material that is being sprayed, the material or object that is being coated or a combination of the two.

What are the benefits of thermal spraying?

This deceptively simple process has evolved from its inception almost a century ago due to its myriad of benefits. These include:

• Cost effective – thermal spraying can reduce costs in a number of ways. For example rather than having to make an entire object from an expensive material, thermal spraying allows the object to be initially made from a low cost base material, that then has the higher cost material coated onto it. Thermal spraying can also be used to rejuvenate worn parts, with a new coating, rather than having to replace the part all together.
• Low heat – although the term ‘thermal spraying’ indicates that heat is used as part of the process, the exact amount of heat can actually be kept relatively low. This can be advantageous as it can keep manufacturing-energy costs down and also means that more delicate materials can be sprayed, which would be compromised by higher heat levels.
• Versatile – due to the numerous different methods and types of thermal spraying that are available almost any combination of material can be sprayed, including metals, plastics and ceramics. The coatings can also be made to a diverse range of thicknesses, from very fine to much more substantial layers.
• Fast – in many cases thermal spraying is one of the fasted ways to apply a coating and in many cases produces some of the fasted drying times.

To find out more about the different types of thermal spray systems that are available and which would be the best fit for your needs, contact the experts at IRS Surfacing Technologies today.