The repair of high-value aerospace components is essential for maximizing part lifetime, reducing operating costs, and maintaining a high level of readiness. Cold spray technologies provided a way to repair some of the most expensive parts, but there are still no practical and economical repair methods for many aerospace components made of aluminum and titanium.
Kermetico HVAF Specialized coating technology and equipment add aluminum and titanium material to worn or damaged areas with outstanding quality:
- Our HVAF Al repair coatings exhibit wrought-like microstructures with near theoretical density values
- Kermetico HVAF Ti coatings for the aerospace overhaul are dense and well-bonded
- Our HVAF systems deposit coatings onto temperature-sensitive materials such as glass or polymers
Our equipment will be good for general re-build of worn or corroded components that have been removed from aircraft during overhaul.
The Kermetico HVAF SL – a Specialized System for High Velocity Thermal Spraying Low Melting Point Materials: Al, Cu and Alloys
The Kermetico HVAF SL is a unique system, specially developed for depositing non-oxidized, dense aluminum, copper and alloyed low melting point metal coatings onto lightweight parts, including aerospace.
- Axial powder injection
- Protection against feedstock oxidation
- No material evaporation in the coating process
- No nozzle clogging
- Uniform, dense, high-bond aluminum, tin, copper and copper alloys coatings
- High spray rate:
- 6 kg/hour (13 lbs./hour) for Al coating
- 10 kg/hour (22 lbs./hour) for Cu, bronze and brass coatings
- Hand-held version is available
- Blast & spray operation capable
- Portable system (air cooling eliminates the need for a water chiller)
The Kermetico HVAF Process Deposits Dense Non-Oxidized Aluminum Coatings
Our HVAF equipment melts Aluminum. But an oxygen depleted flame and inert gas prevent Al from oxidizing, both in the jet and on the surface, and the high-speed jet creates a high bond and low porosity coating, so our HVAF SL system deposits excellent quality Al coatings.
And we make Al layers with no nozzle clogging and no oxides in the coating structure.
The Kermetico HVAF STi System for Thermal Spraying Titanium and Alloys onto Aerospace Parts
Our HVAF STi gun is designed to deposit titanium and its alloys in air;
- High-velocity titanium spraying in an inert gas shroud
- Low level of oxidation, silver-like coating appearance
- Dense coating
- For corrosion resistant coatings and material build-up
STi – one of our latest developments, and we are still researching its possibilities.
The Properties of Ti and Titanium Alloy Coatings
Titanium is not an easy material to spray. It reacts with Oxygen and Nitrogen at relatively low temperatures.
That is why most developers were trying to deposit it with a vacuum or an inert gas atmosphere.
These approaches make the coating extremely expensive.
We have chosen a different approach, creating an inert atmosphere inside the high velocity thermal spray gun.
But it is true.
The particular design of this unique thermal spray system keeps Ti powder in the inert gas atmosphere all the way through the thermal spray gun until it meets the substrate and bonds there.
An observer will notice in the photograph above that the Titanium jet is several times narrower than the nozzle and starts oxidizing around 150 mm (6”) from the nozzle.
The Thermal Spray Restoration of Worn-out Aviation Titanium Alloy Parts
Designers use titanium alloys widely in aircraft, ships, and spacecraft due to their high tensile strength to density ratio, high corrosion resistance, fatigue resistance, high crack resistance and ability to withstand moderately high temperatures without deformation.
Many attempts have been made by different research bodies to repair titanium alloy parts with cold spray, laser cladding, and other techniques.
Most of them have failed and had to resort to applying alternative materials onto the worn areas.
As far as we know, the question of the MRO restoration of titanium parts is still open.
With the introduction of the functional titanium STi system, we provide an instrument for high-quality repair of titanium alloy workpieces.
The HVAF Process Description
The HVAF SL and STi Guns spray powders, heated and accelerated by the air-fuel gas combustion products.
The mixture of compressed air and the fuel gas flows into the combustion chamber through the orifices of a catalytic ceramic insert.
The initial ignition of the mixture results in the heating of the insert above the mixtures’ auto-ignition temperature and then the hot insert continuously ignites the mixture.
When entering the gun, the compressed air cools the chamber and the nozzle assembly.
Then part of the preheated air is mixed with the fuel and ignited.
The spray powder is injected axially into a wide combustion chamber.
The powder exiting the chamber is propelled into the nozzle of chosen length and configuration where it is accelerated to a velocity that may be over 1,000 m/s.
When impacting a substrate the spray powder particles form a coating.
Kermetico HVAF Thermal Spray Coating Equipment
We design and manufacture three families of HVAF thermal spray equipment.
- Convertible HVOF and HVAF equipment:
- Multi-purpose HVAF AK systems, with a variety of spray guns:
- AK7 – a high-power gun for the thermal spray of large parts
- AK6 – a gun to spray tungsten and chromium carbide onto a balanced mix of parts
- AK5 – a compact gun to spray smaller parts, thin walls and complex surfaces
- AK-ID – an 80 mm (3.15”) and larger internal diameter spray gun
- AK-IDR – a rotating ID gun to spray 4” (100 mm) and larger bores
- AK-HH – a handheld gun for on-site coating
- Specialized equipment:
- SL – a specialized gun for spraying low melting point metals – recommended for MRO
- SP – a dedicated gun for the most efficient precious metals’ deposition
- STi – a specialized gun for the deposition of titanium and Ti-alloy coatings
- Additional equipment:
Kermetico: HVAF and HVOF Equipment Design and Manufacture Since 2006
We make different spray guns for various applications.
Please check the full spectrum of our equipment here.
Our HVAF systems operate each of our guns or multiple guns at once (by request).
We supply two types of control consoles and a variety of powder feeders and gas vaporizers.
We proudly design and produce our HVAF thermal spray equipment in California, USA, and install it all over the world.
You can visit our R&D center in Benicia to meet our designers and to see our HVAF equipment in action.