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5 Advantages of the Cold Spray Coating Process

Repairing or replacing equipment in your organization can be expensive and time-consuming. When a vital piece of equipment craters, the expense of repairs doesn’t stop at the machine. The Cold Spray Coating Process can reduce or eliminate downtime, and provide several other benefits to companies that make and fix products. 

VRC Metal Systems​ partners with you to deliver customized cold spray coating process solutions to keep your operation running smoothly and reliably.  

Contact us today to discuss your needs and find out how cold spray technology can be a top asset in your company. 

Recent but reliable 

The cold spray coating process was first discovered in the mid-1980s at the Russian Academy of Sciences, but it wasn’t until the late-1990s that it was first patented in the U.S. and began to pique the interest of national labs, aerospace companies and the Department of Defense.  Now, after more than two decades of research and development, cold spray is solving real-world problems most people never dreamed would be possible.

The cold spray coating process combines coating particles with high-pressure gas and accelerates them to supersonic speeds through a nozzle and onto a surface. The coating particles bond to the desired surface without the chemical and molecular changes that accompany other high-temperature spray applications. 

In short, the cold spray coating process presents several advantages for equipment repair. With cold spray technology, you can prolong equipment life, reduce downtime, save money on new equipment purchases, and reduce labor costs attached to equipment repair. 

Airplane mechanics checking jet engine if civil aircraft

 A detailed look at how to use the cold spray coating process to your advantage 

Unlike high-temp bonding applications, the cold spray coating process does not remarkably change the base materials that are coated. During the coating process, all materials remain in a solid-state, as opposed to the physical changes that can occur with high heat, like melting and phase transformation. 

As a result, the sprayed metal particles experience reduced oxidation, and surface oxides are literally blasted away by the impacting particles, which assists the bonding process. Further, the bonded section does not shrink after the application from solidification, as materials do during other high-temp thermal spray and weld coating processes. 

Because of the extremely high pressure applied to the spray coating and the velocity they achieve upon exiting the supersonic nozzle, the sprayed particles bond as if they were  Play-Doh thrown at the substrate surface.  

Think of the cold spray coating process like tiny particles of sprayed coating essentially “hugging” tightly the particles on the substrate surface. A molecular embrace like the one described is difficult to break. It’s essentially a mixture of metallurgical and mechanical bonding, that is so good, the coating is often indistinguishable from the substrate. 

Cold spray particles exit the “gun” in a narrow “beam.” This precision affords greater accuracy in the coating application and offers more coating thickness options and shape control than thermal spray methods. 

The best materials for spray coating and substrates 

 Coatings:  

  • Titanium 
  • Copper 
  • Stainless Steel 
  • Aluminum 
  • Alloys of the above materials 
  • Ceramics (must be applied as a composite, not in pure form.) 

copper texture

The best surfaces for cold spray bonding include any surface that can withstand the high-pressure cold spray coating process. Soft substrates would likely erode under the pressure-sprayed particulates. The same is true for friable surfaces.  

Industrial relevance 

To date, the cold spray coating process is commonly used in: 

  • The aerospace industry (for example, in aluminum coatings to refurbish or protect magnesium components)  
  • Heavy Industrial shafts and cast iron engine casings 
  • Nuclear fuel rod coatings and component repairs 
  • The cookware industry (ferrite coatings on certain conduction cookware pieces) 
  • Near net shapes, performance-enhancing layers, free forms 
  • Turbine component coatings
  • And many more we just can’t talk about…

cookware

The industrial applications for cold spray evolve continually with technology advancements and capabilities

The cold spray coating process advantage 

Above, we discussed the physics and structure of cold spray bonds, which can preserve the metal composition and bond size of the spray particles and the substrate surface. There are several other advantages of using cold spray technology. 

  1. Cold spray is portable​: This technology may reduce or eliminate the need to pull machinery off a production line or disassemble equipment to access the surface to be fixed or coated. Cold spray guns are agile and can fit into a variety of spaces while applying reliable bonds and coatings of precise thickness. 
  2. Cold spray is fast​: Because this technology eliminates several steps from a conventional high-temp bonding process, repairs occur in a fraction of the time. There’s no need for “cooling” from a hot bonding application. You can often achieve a “shoot-and-start-up” result from a cold-spray bond.  
  3. No bulk particle melting​: Because of the high-pressure bond created by cold spray, melted particles are not necessary for the process. 
  4. Enables thicker coatings​: Because of the elimination of ​solidification stress​ (stress or deformation on the substrate surface as it hardens after high-temp bonding), you’re clear to thicken the coating dramatically, at a lower risk. 
  5. Decreased surface prep​: The cold spray coating process often reduces the need for grit blast on the substrate surface. Because of the narrow particulate stream, you may also reduce or eliminate masking on the substrate surface. 

Other cold spray coating process advantages 

Since cold spray technology does not compromise either the particle or substrate structure during the bonding process (remember the molecular “hug” we talked about earlier?), bonds, coatings, and repairs may last longer than in welding or other thermal spray applications.  

Spray flow from aerosol can on black background.

When your equipment lasts longer, you save money in the long run with reduced capital expenditures on machinery. Furthermore, your production line or other services can enjoy more “up” time over the life of your equipment. 

 Both of these scenarios mean more revenue potential with fewer operation interruptions.  

With the agility of a cold spray system, you may also save significantly on labor costs in your shop. Your maintenance staff can pinpoint the part or machine in need of repair or coating, and shoot a coating onto the desired seam, joint, or part with increased dexterity and speed. 

VRC Metal Systems knows cold spray technology

With services ranging from on-site equipment training to sourcing additives to equipment leasing, VRC Metal Systems is an end-to-end partner in developing your cold spray solutions. 

Our customized approach means we strategize, source, and develop the right equipment, tools, and materials to meet your coating needs. We also stay on the leading edge of cold spray technology innovations and remain able to solution-find on demand for our clients.

Contact us​ today to set up a cold spray technology consultation, and see in real time how you can benefit from using the cold spray coating process in your operation.

Extending Product Life Through Cold Spray Technology

Replacing worn-out or damaged products presents a variety of challenges for any company. Extending product life cycle stages as much as possible is the goal of many an Operations Director or  COO. 

The cost of replacement can be prohibitive as well as unexpected when a part breaks down. Plus, replacing equipment often means significant downtime for your production line, repair services, or other industrial applications. 

 VRC Metal Systems drives its service with these challenges at heart. Our custom-designed cold spray technology solutions help your organization remain nimble, prolong product life cycle stages and function, and increase your operational “up-time.”  

Contact us today​ to begin collaborating on your next repair project, and preserve the life of your equipment indefinitely with cold spray technology. 

What are the benefits of cold spray repairs over other methods? 

Contractor's hand with brush that painting metal construction.

Cold spray coating works by shooting pressurized gas and small particles of coating material through a nozzle at a very high velocity. The high kinetic energy of the accelerated particles deforms and activates on impact the surfaces enough to bond molecularly with a substrate material. 

 Cold spray technology differs from thermal coating methods in that both the coating and the substrate heat up, but just enough to bond tightly without becoming molten.  

 During the spraying process, the additive and substrate particles “plasticize,” meaning they mold around each other almost as if they were warm plastic, and the high velocity impact blasts away surface oxides, allowing a true metallurgical bond to form between impacting particles. 

 Some of the advantages to a cold spray coating process over a thermal one are: 

  • Heat-sensitive alloy compatibility 
  • Low thermal stress 
  • It does not require an inert environment (you can apply cold spray coatings in a variety of settings.) 
  • Can process metals prone to cracking in thermal coating applications 
  • Reduction or elimination of oxidation in an open environment 
  • Choose high pressure for depositing high strength metals (like steel and titanium alloys)  and to achieve the best properties (even for softer materials like copper and aluminum) 
  • 3D printing capabilities as near-net-shapes 
  • Formation of dense, strong bonds with high rates of deposition 
  • Potentially dramatic cost savings over thermal coating methods 
  • Nimble application–you may be able to repair equipment with cold spray technology without equipment  removal from your line, or component removal from the product 
  • Low material waste–with minimal masking and high deposition efficiencies 
  • Energy-efficient technology, which may lower your carbon footprint 
Polyurea Spraying, warming foam coating of roof, focus on wall.

Cold spray can be used again and again on the same bond

While​ repeated welding can increase the risk of corrosion in some materials​, cold spray technology does not share this risk. In effect, cold spray remains an effective repair method no matter how many times you coat the same surface. 

 Remember, cold spray bonds do not shrink from solidification or sensitize the substrate as other thermal coating processes may. The resilience of CS coating is superior in many applications. 

 Also, cold spray systems can adapt to just about any working space and do not need specialized environments in which to be effective. Your cold spray technology goes where you need it to, and bonds to surfaces reliably and repeatedly. 

Industrial applications for cold-spray repairs 

B-1 aircraft hydraulic lines often chafe during use. These lines are made of titanium, a light-weight and formable metal that is necessary to bend around the tight spaces inside the aircraft. However, titanium is also vulnerable to chafing wear, surface scratches, and other “dings” can negatively impact the line’s safety and function. 

These lines (notoriously) often need replacing, which gets expensive and time-consuming quickly, making it one of the most common and costly maintenance items on the aircraft. Cold spray technology has been shown to increase the product life cycle stages in these titanium hydraulic lines by laying down a protective titanium coating in high-chafe areas to extend their service life. 

Inspectors can discern between the coating and the actual tube by the varying degrees of reflectivity in the tubing material versus the cold spray coating.  

Surveyor inspecting ship in floating dock

Safety inspectors can also use ultrasonic thickness inspection to determine when chafing through the protective layer on the hose surface threatens to expose the tube itself. When the protective layer wears thin, repeated CS coating layers can be applied to reinforce the chafe area and prolong the titanium tube’s life indefinitely. 

CS coating over replacement saves time and money each time a new coating is applied 

Further, using helium as the propellant in this application prevents a brittle crust, or alpha case from forming around the coated area of the line. 

Cold spray technology can also extend the product life cycle stages of parts of equipment made of titanium, magnesium, and related alloys.  

The ability to apply cold spray coatings without completely disassembling machinery or production lines makes this technology an obvious repair choice in many instances. 

Think of cold spray coatings for finished product repair (aircraft engines, automobiles) as well as for the machines that create them (coating, protecting, repairing production line equipment.) 

The automotive industry also continues to expand its use of cold spray technology by coating synchronizer and pistons to extend their lives. The auto-body industry also uses cold spray more and more for bonding and protective coatings. 

More repair possibilities for cold spray technology 

Several other industrial applications for cold spray coatings look promising, and can provide a foundation for expanding cold spray’s use.  

Cold spray helps protect the turbines in jet engines by repairing small flaws in superalloy components, that if left untreated could become a critical failure down the road. This technology also lengthens the part life cycle in older naval ships and their components.  

In the medical industry, cold spray can provide antimicrobial copper coatings to create self-disinfecting surfaces that prevent the formation of biofilms to help reduce hospital acquired infection rates and slow the spread of other contagious bacteria and viruses from common touch surfaces.

Close up image of rusty metal structure, corrosionPartner with VRC Metal Systems to increase your product life cycle stages VRC Metal Systems leads the industry in customized cold spray applications. Whether your goal is to repair, protect, or create in your operation, the team at VRC Metal Systems can build or curate the right equipment for the job. 

Our intimate and evolving experience with a wide variety of cold spray applications makes us adept collaborators on developing new cold spray solutions. We work with and for a wide range of industries, and our cold spray innovations evolve continuously. 

Contact us today​, and we’ll get in touch to discuss your needs and provide the cold spray technology strategy and implementation you require.

Metal Repair and other Shipyard Activities

There are nearly one hundred shipyards around the United States and hundreds more around the globe. Activities at these shipyards include:

  • Constructing a wide range of new vessels such as passenger ferries, cargo ships, liquid natural gas tankers, warships, or even research submarines
  • Performing metal repair and maintenance procedures.
  • Upgrading existing ship technology and materials.
  • Applying for the latest corrosion protection.

The shipbuilding industry’s goal is to keep people and products moving safely across our lakes and seas. This movement is critical to ensure that commerce functions without interruptions, scientists can complete research, and warfighters can defend us and our allies.

Many shipyards may have had a history similar to that of the Puget Sound Naval Shipyard in Washington. This shipyard was established in 1891.

The Puget Sound Naval Shipyard started building ships during WWI. During WWII, their main focus was repairing battle damage to the naval vessels of the US and its allies.

After WWII, they changed direction and concentrated their efforts on modernizing existing craft until significant developments in marine technology appeared, creating the need for new vessels once again.

Whenever metal repairs or the application of corrosion-resistant coatings are needed, VRC Metal Systems is at the forefront of cold spray technology. Learn more about our products and capabilities here.

Read on to learn more about the different activities involved in building, repairing, and modernizing today’s ocean-going vessels.

Low angle shot of a hull of ship in drydock resting on pilings ready for launch

Shipbuilding

The original purpose of most shipyards was to build ships. In Colonial America, the primary need was for fishing vessels. As water trade increased, so did the need for larger dry-cargo ships.

Originally, hulls were made of wood frames. Wood planks were heated and warped to form curves around the frame. These planks were then made water-tight with pine tar. The pine tar was mixed with fibers to form a type of caulking to seal any gaps between the planks.

Copper plating was often attached to the hull with brass nails to create the earliest form of corrosion protection, and to keep the hull from being infested with woodworms.

The invention of the steam engine and processes for extracting steel and other metals came with the onset of the Industrial Revolution. With these innovations came new designs which radically changed shipbuilding.

Initially, metal replaced critical sections of the wooden hulls where sharp joints or corners were required. Eventually, that use expanded to metal plates bolted together to form the entire hull.

The two World Wars contributed to a significant expansion in the shipbuilding industry as more and more vessels were needed to transfer soldiers and war material around the world. Only two dry-cargo ships were built in the fifteen years before WWII in the United States.

In contrast, 2,710 Liberty-class cargo ships were built in the United States between 1941 and 1945.

The Victory-class cargo ship succeeded the Liberty design with a more powerful steam engine. The more powerful engine made this slightly larger vessel faster and able to out-maneuver German U-boats.

After World War II, international trade skyrocketed, and so did the need for larger and larger cargo ships.

Man working with a torch on a propeller of a ship in drydock

Metal Repair

With all those cargo ships now traversing the oceans, they will need repair at some point. They will need repair from damage sustained during battles, running aground, or deterioration caused by a harsh seawater environment.

Thus, the next phase in the lifecycle of a shipyard.

The ship’s crew can perform much of the needed maintenance while at sea or in port. However, some repair and maintenance can only be completed in a shipyard under the supervision of classification societies such as Lloyd’s Register or Bureau Veritas.

The classification society designates a ship’s class. That designation defines the set of technical rules and standards that must be followed to keep the vessel and its crew safe.

The society also periodically surveys vessels to ensure the machinery and equipment is built and maintained to those prescribed standards.

Drydocking has been employed at shipyards for decades for manufacturing, as well as completing necessary repairs. The purpose of drydocking is to expose surfaces and components below the waterline for metal repair, replacement, or upgrades.

According to SOLAS (the International Convention for Safety of Life at Sea), a ship may be required to submit to a bottom survey as often as every two years, depending upon its classification.

Two of the most common operations performed in dry dock include inspections and hull and propulsion repairs.

Submarine in partially submerged in water at a naval shipyard

Modernizing

Additional tasks in or outside of dry dock can include upgrades to systems, components, and materials, such as:

  • Adding fiber optics and other state-of-the-art communication upgrades.
  • Upgrading propulsion plants and controls.
  • Adding alarm and monitoring systems
  • Increasing desalination capacity.

An additional modernization is the use of the latest cold spray technology to complete metal repairs or add corrosion-resistant materials to existing componentry. Cold spray is a method for applying metals, metal alloys, and metal blends to an existing substrate.

Cold spray technology can be used to:

  • Repair damaged surfaces.
  • Create dimensional restorations or added features.
  • Add corrosion- or wear-resistant coatings.

Rather than removing a compromised component or metal section for transport to a separate repair facility, portable cold spray technology, like the one developed by VRC Metal Systems, can be brought on-site for use.

The shipyards have come a long way since building wooden-hull fishing vessels. Submarines and research vessels are now familiar sights in shipyards as well, requiring inspection and repair.

Cold Spray for Any Point in a Vessel’s Lifecycle

Build, repair, modernize, repeat – apply cold spray technology at any point in the lifecycle of the modern shipyard.

Whether creating a new design feature or adding wear- or corrosion-resistant coatings, the highly experienced staff at VRC Metal Systems, can get you started with the right solution.

There is no need to disassemble that equipment and wait for it to come back from the repair facility. Our cold spray system is portable and high pressure, providing cost- and time-efficient metal repairs.

Previous cold spray repairs that have experienced damage can also be re-repaired using cold spray. Contact us today.

Cold Spray Coating Process Protects Against Various Types of Corrosion

Shipping, manufacturing, energy, and everyone else across the industrial sector have the same boogieman plaguing their machinery, corrosion. That ugly chemical reaction can cost millions of dollars of problems. Not only is it expensive in upfront repair costs, but so is the downtime of the machine needing repairs. Luckily there is a solution — cold spray.

The cold spray coating process offers excellent corrosion prevention and repair without the risk that other thermal spray coatings and weld overlays present to completed components. Its high strength and lower input make it an excellent anti-corrosion solution for machines undergoing repairs.

The cold spray coating process is the safest and most cost-effective anti-corrosion solution on the market. For your future cold spray coating needs, VRC Metal Systems is here for you. Contact us today and let us keep your components safe from corrosion.

Corrosion and its various forms

In our respective industries, we build components to last and having an inadequate anti-corrosion coating, or worse-yet no anti-corrosion coating is an unnecessary liability. Corrosion does not just affect the aesthetics of your equipment, but it creates a safety risk as well.

The uniform orange-colored oxide that we find on mild steel is initially benign and easy to treat. Not all corrosion types are that simple to address, and more advanced forms of corrosion can create nightmares. It’s always better to avoid corrosion in the first place, but let’s describe the types of corrosion that we find most commonly.

Close up image of rusty metal structure, corrosion

Pitting Corrosion

Pitting comes from several sources; one of its most common causes stems from an initial failure point in the protective coating of an object. The attach starts with a small pinhole in the surface and, from there, will begin to wreak havoc.

The corrosion will eat deep into the structure in a vertical attack and may remain relatively localized Other times it can branch outward weakening large sections of the substrate.

Because this corrosion starts so small, it is hard to spot before it becomes too late. If left unchecked, pitting corrosion will result in structural damage and necessitating complete replacement of the component.

Luckily, the cold spray coating process is the perfect solution to this problem. It is a very durable and highly dense coating that can protect a component’s surface from pitting corrosion. It can also be applied as either an anodic or cathodic protection coating, depending on the application, so the substrate below will never experience corrosion-prone conditions.

Intergranular Corrosion and Stress Corrosion Cracking

Intergranular corrosion occurs when impurities in the metal cause oxidation at the grain boundaries. When visually inspected, this corrosion will appear as extremely small cracks on the surface. The corrosion often has shiny clean-looking metal around it and can be missed when checked at a glance.

This corrosion doesn’t have the telltale bubbling or discoloration seen in pitting or uniform corrosion. While appearing structurally sound, this type of corrosion will affect the mechanical properties such as strength, stiffness, and cracking resistance in the metal.

Intergranular corrosion most often occurs from prolonged and extreme heating of a metal component. In particular, welding is a common cause of this effect, and it has a distinct term called weld decay. This cracking effect can also occur by a metal operating in a caustic environment, and when under tensile loading, this phenomenon is known as stress corrosion cracking.

Having a cold spray coating applied to welded materials, or those operating in a caustic environment is the best way to prevent intergranular and stress corrosion cracking. The low-temperature nature of cold spray coatings keeps excessive heat from being applied to a material, and yet it still has unsurpassed strength when compared to many other coatings.

Rusty steel nut and bolts on a gray steel lamp post plate

Galvanic and Crevice Corrosion

Crevice corrosion occurs in areas where two surfaces mate, such as under a washer or the head of a fastener. As the oxygen content in the environment becomes depleted, the acidity begins to rise and corrode the surfaces involved. If left unchecked, this can lead to significant structural degradation, as well as pitting and other forms of corrosion.

Crevice corrosion is very similar to galvanic corrosion, which occurs when there is a transfer of electrons from an anode to a cathode. This effect is a common form of corrosion when mixing two metals that have different electrochemical potentials and therefore react with each other in the presence of an electrolyte (such as saltwater), as for example with aluminum and stainless steel.

While molybdenum disulfide (MoS2) coatings on hardware can help prevent this corrosion between the mating surface and the fastener, applying a cold spray coating can provide a more durable and reliable solution when applied to the mating surfaces.

The cold spray coating process could be an excellent solution for your mating surface challenges. The long term quality of the protective coating in this instance is paramount since preventative inspections can be costly and even require disassembly of the component.

How does Cold Spray Coating improve upon other types of protective coatings?

The cold spray coating process provides superior corrosion protection over its competition in almost every form. While some coatings might be well suited for a particular niche, cold spray coating is exceptionally versatile.

  • Sol-Gel Coating: While Sol-Gel is a good technology and has its uses, its propensity to delaminate raises severe concerns for long term reliability.
  • Powder Coating: Provides protection only as long as the surface remains sealed. Once the coating is damaged, it can promote crevice corrosion. Also, the requirement to heat the coating for curing can damage some sensitive components.
  • Anodizing: Anodizing works well for non-ferrous metals; however, the harsh acids have a significant environmental footprint. The facility is also in a permanent location, and travel time means more downtime.

Cold Spray is the highest quality, most environmentally-friendly option for an anti-corrosion coating on the market today. It provides a strong and durable coating that doesn’t require excessive heat or harsh acids to apply to the component. The versatility of this coating is an excellent complement to its stellar performance as an anti-corrosion coating.

Portable cold spray equipment with VRC logo

VRC Metal Systems is here for you

Why find yourself replacing corroded components or waiting for some time-consuming coating process to be completed when you have a better option? The cold spray coating process is fast, versatile, and, most importantly, it’s durable. VRC Metal Systems is here to help you with your cold spray coating needs, contact us today and let us give your components a longer life.

A Beginner’s Guide to Cold Spray Terminology

Automotive, Aerospace, and Mining Industries, among many others, currently use cold spray technology for the cost-effective repair of metal componentry. These repairs include the reformation of cosmetic features, enhancing metallurgical qualities, and completely rebuilding physical attributes.

According to the experts at VRC Metal Systems:

“Cold spray, referred to as supersonic particle deposition, is a high-energy solid-state coating and powder consolidation process. Cold spray uses an electrically heated high-pressure carrier gas, like nitrogen or helium, to accelerate metal powders through a supersonic de Laval nozzle above a critical velocity for particle adhesion. The bonding mechanism is a combination of mechanical interlocking and metallurgical bonding from recrystallization at highly strained particle interfaces.”

Well, that was certainly a mouthful. Let’s look a little more closely at each of those terms, some additional industry vocabulary, and see if we can all speak the same language. Then, contact the experts fluent in cold spray technology at VRC Metal Systems to partner together on your next cold spray technology solution.

Five industrial helium canisters of varying sizes

The supplies

Let’s start with the physical items needed to apply cold spray technology.

Alloy: a blend of metals (or other elements) in solid solution. Steel is an example of an alloy of iron and carbon, often containing other alloying elements as well.

Metal powder: a powder consisting of a single, pure metal. Size range for cold spray ranges from 5-100 micrometers in diameter.

Alloy powder: powder created from a single molten alloy

Composite powder: a powder combining particles with two or more individual materials

Process gas: provides the driving force for accelerating the metal powders. The Process Gas is heated prior to being blended with the carrier gas and injected into the De Laval nozzle.

Carrier gas: the gas conveying the powder from the powder feeder through to the surfacing gun

Helium: a low density inert gas used for filling balloons and airships. Often used in the cold spray process due to its high speed of sound.

Nitrogen: another inert gas often used as a carrier gas in cold spray technology. Nitrogen makes up over 78% of the earth’s atmosphere, yet it will not support life or combustion. Nitrogen gas is cheap and widely available, however it has a lower speed of sound and cannot achieve the particle speeds that helium can.

De Laval nozzle: a nozzle that converts heat energy in the gas to kinetic energy (speed!). A slow and high temperature gas goes in, and a fast and lower temperature gas comes out.

Substrate: the base material to which the coating is applied

Although far from an exhaustive list, the above items cover the basics. Now let’s move on to the cold spray process itself.

Flow regulator gages

The process

The cold spray process is a supersonic particle deposition where the powder is accelerated to a critical velocity by an inert gas. The resulting bonding is a combination of mechanical interlocking and metallurgical bonds from the recrystallization of highly strained particle interfaces.

Here’s a look at some of the terms related to that description.

Feed rate: The rate at which the consumable metal, alloy, or composite powder is fed through the cold spray device.

Gas flow rate: the rate at which the gas, usually measured in liters per minute, flows through the spray nozzle.

Deposition rate: the weight of material deposited onto the substrate over a given time, usually measured in kilograms/hr (kg/h) or pounds/hr (lb/h).

Critical velocity: the speed at which a spray of particles transitions from eroding the target surface to coating the target surface.

Mechanical interlocking: a mechanical mixing or blending of the impacting particles and the substrate or previously deposited layers of particles that effectively interlocks the layers together. This interlock can transfer load and resist motion even if the particles are not metallurgically bonded to the substrate or other particles.

Metallurgical bond: is the type of chemical bonds between atoms in a metallic element. Metallic bonding is what yields property characteristics in metals such as ductility, conductivity, and strength.

Recrystallization: new grain formation within the metal structure, often occurring to replace highly deformed (strained) grains. Dynamic recrystallization in the cold spray process can result in nanograin formation, which resists dislocation movement (high strength).

Plastic deformation: when a particle changes shape due to applied stress, pressure, heat, or force. The forces break atomic bonds, and the deformation is permanent.

Elastic deformation: deformation in a material below the yield strength that is fully recovered when the load is removed. This is similar to stretching and releasing a spring.

Metal part being cold sprayed

The results

Once again, from the experts at VRC Metal Systems:

“The cold spray process is applicable to corrosion-resistant coatings…, dimensional restoration and repair …, wear-resistant coatings …, electromagnetic interference (EMI) shielding of components and structures, high strength dissimilar material coatings for unique manufacturing solutions, and field repair of components and systems.”

And that would mean…

Corrosion: the chemical or electrochemical reaction of the substrate material with its environment leading to the deterioration of the base component. Rust is a typical example of electrochemical corrosion.

Wear: loss of material from a component surface due to some mechanical action such as erosion, abrasion, or fatigue.

Electromagnetic interference (EMI) shielding: using conductive or magnetic materials to form a barrier against electromagnetic fields. Electromagnetic shielding that blocks radio frequencies is known as RF shielding.

Field repair: Portable cold spray systems allow you to take the solution to the component, which is an extremely cost-effective way to handle the extensive component repair.

The benefits

In addition, some of the benefits of applying cold spray technology include:

Bond strength: the strength of the adhesion between the coating and substrate. For cold spray, this is typically > 10 kilopounds per square inch (KSI).

Coating strength: also referred to as spray deposit strength. Typical values achieved exceed 40 ksi.

Porosity: the amount of void space in a material, usually below 1% for cold spray coatings.

Oxidation: chemical reaction on the metal surface that occurs at high temperatures. Cold spray temperatures are low enough that no oxidation of metal powders occurs in the deposition process, leading to little to no oxide contamination in the coating.

Heat affected zone: the area of the substrate that increases in temperature due to coating application. Cold spray has inappreciable heat input, thereby minimizing the heat-affected zone.

Overspray: the portion of feedstock not deposited on the substrate. Cold spray technology achieves tightly focused particle spray paths, which minimizes the overspray.

The terminology detailed above is a rudimentary list.

The engineers at VRC Metal Systems have been working to commercialize this technology alongside engineering experts from the South Dakota School of Mines and Technology (SMSM&T), the Department of Defense, and the Army Research Laboratory for over ten years.

These solutions have military, as well as commercial applications.

VRC Metal Systems has the only high pressure, portable cold spray system on the market. This combination of technologies has transformed the process applications.

Today, there is little need to disassemble equipment and bring large bulky plates to a repair facility. VRC Metal Systems sprayers go to the site, providing for cost-effective repairs and restorations.

Now that you’re familiar with some of the basic terminology used in the cold spray industry, contact the experts at VRC Metal Systems who truly speak the language. We’ll start working towards your next project solution.

Cold Spray vs Thermal Spray – An Overview

What do the aerospace, shipping, oil, gas, and mining industries all have in common? They have high-dollar components that cause even higher-dollar down-time when they require repair or replacement. 

These industries have traditionally relied on thermal spray processes, like flame spraying and arc spraying. These modalities have been in development since the early 1900s, to repair and enhance original equipment.

Plasma spraying, another method of equipment repair, arrived in the industry about 50 years later in the ‘70s.

Cold spray processes are a much more recent development, gaining popularity in the 1990s. Portable, high-pressure, cold spray equipment, like that developed by VRC Metal Systems, is at the forefront of this emerging technology.

You can find more information on cold spray vs. thermal spray below. To determine how cold spray technology may apply to your next project, contact the experts at VRC Metal Systems.

Ocean going vessel in dry dock for repairs

Cold spray

What is it?

Cold spray is a coating deposition process in which powdered material is accelerated to supersonic speeds, as high as Mach 3. The accelerated powder deposited onto a similar or dissimilar material surface. The powders reach high velocity using a high-pressure, electrically heated carrier gas, like nitrogen or helium.

Sending the gas and powders through A de Laval nozzle accelerates the powder to supersonic speed. The de Laval nozzle is a tube that contains an internal asymmetric hourglass shape and converts the heat energy of the flow into kinetic energy. Jet engines and steam turbines also use these types of nozzles.

Once the particles achieve these high speeds and impact the material surface, the particles undergo a plastic deformation causing them to bond to the target surface. The mechanical interlocking of the particles, as well as recrystallization at the surface interfaces, creates a strong bond between particle and surface.

There are two types of cold spray:

High-pressure cold spray (HPCS) – uses nitrogen or helium, has a flow rate of more than 2 m3/min, and is used for spraying pure metals. 

Low-pressure cold spray (LPCS) – uses a compressed gas, with a flow rate up to 2 m3/min, and is used for flowing a mixture of metal and ceramic powders.

Using cold spray

Cold spray powders use a mixture of metallic and non-metallic compounds. These mixtures allow for the application of material coatings, the repair of a surface with similar or improved materials, or the creation of free-standing components by spraying onto a substrate and then removing the original substrate base.

Cold spray materials often combine to create wear-resistant coatings, improving the life-cycle of a component subject to severe conditions. By using zinc or aluminum, the cold spray process provides a corrosion-resistant coating, perfect for marine applications. 

This process alters or repairs aluminum, nickel, or titanium components, among many others. Dimensionally modifying or repairing the original piece is most often a more economical solution to replacing the component completely.

Why is it used?

Cold spray is a “green” type of technology. There is no chemical heating process required, which results in no toxic fumes, and reduces CO2 emissions.

Due to the focused particle spray path, minimal masking of the substrate area is required, and there is no heat-affected zone either. There is also no oxidation, alloy decomposition, or combustion product entrapment with a cold spray process.

Using cold spray is also an extremely cost-effective alternative to replacing the whole part. For example, a 40” x 40” panel on a B1 bomber costs around $250K to replace. Depending upon the extent of the damage, you can repair this same panel using cold spray technology for around $10K.

The portable cold spray equipment developed by VRC Metal Systems also makes cold spray the optimal solution for parts where removal for repair is not an option.

Gas turbine engine and gas compressor with piping and tubing accessories at oil and gas central processing platform.

Thermal spray

What is it?

Thermal spray is another coating deposition process. However, the material in this process is in the form of molten, or semi-molten, droplets that are sprayed onto a surface. The materials used can be heated by electrical or chemical means. 

Typical materials include metals, ceramics, and polymers, but can include anything that melts or becomes plastic during the heating process. You can typically use thermal spraying to apply coatings of .1 to 10mm in thickness. 

A thermal spray bond is mechanical in nature, not metallurgical or fused. The condition of the substrate surface is critical and must be clean and roughened before spraying.

Below, we provide more information on the several types of thermal spraying.

Plasma spraying: uses an electrical means to heat the coating material. An electric arc forms a high-temp plasma jet. The coating material feeds into the plasma jet as well as an inert gas, which expands rapidly to create a high-velocity spray of particles.

Arc spraying: is another process that uses an electrical means to heat the coating material. An electrical arc initiates between two coating material sources, causing them to melt. Compressed air atomizes the coating and propels the droplet towards the desired surface.

Flame spraying: uses a chemical means of heating. A fuel gas such as propane or hydrogen, and oxygen, mix to heat the coating material either in wire or powder form. Inert gas propels the coating at the substrate.

HVOF (High-velocity oxy-fuel) spraying: is another chemically heat produced process. The heat and pressure generate from combusting a liquid or gas fuel mixed with oxygen. The spray particles heat and expand in a chamber forcing the exhaust gases out at supersonic speeds towards the substrate.

How is it used?

Similar to cold spray, thermal spray produces coatings on substrate materials, enhancing the original materials characteristics, changing their appearance, creating dimensional repairs, or creating free-standing components by removing a shaped substrate after coating.

Thermal spray coatings help significantly in the manufacturing and repair of oil field equipment, diesel engines, gas turbines, and coating medical implants.

Why is it used?

One of the main advantages of using thermal spray is that thick coatings can be applied at high deposition rates. Thermal spray can be used as an alternative to nickel and chrome plating, nitride or heat treat processes, weld overlay, or anodizing.

Like cold spray, thermal spray can repair parts at a fraction of the cost to replace the same part. Using thermal spray to apply wear-resistant coatings can also extend the life of a component.

Cost-effective restoration and repairs

VRC Metal Systems has revolutionized the process of applying cold spray technology. Our cold spray system is both high-pressure and portable and provides fast, cost-effective restoration and repairs.Contact us today to find out how we can support and improve your next project with our cold spray products and services.

Contact VRC Metal Systems

Call, email, snail mail or visit the VRC Metal Systems offices today to talk to a representative about how your business can benefit from our cold spray systems and service.

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605.716.0061

VRC Metal Systems
600 N Ellsworth Rd
Box Elder, SD 57719

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