HVOF Systems (High Velocity Oxygen Fuel)

High velocity oxygen fuel (HVOF) systems use a high velocity jet into which the spray powder particles are injected, the jet being formed by the combustion of oxygen and fuel, which is heated and accelerated towards the component being Thermalspray coated.

HVOF coatings are very dense, strong and show low residual tensile stress or in some cases compressive stresses, which enable thick coatings to be applied in comparison with other metalspray processes.

The very high kinetic energy of particles striking the substrate surface does not require the particles to be fully molten to form high quality HVOF coatings. This is certainly an advantage for the carbide cermet type of HVOF coatings.

HVOF coatings are used in applications requiring the highest density and strength not found in most other thermal spray processes. New applications are being discovered, including as a Chrome Plating replacement.

Metal Spray Supplies offer their customers both high and low-pressure HVOF systems.

Metallisation Met Jet HVOF System

Met Jet attributes:

• Thick low stress coatings
• High hardness
• Low oxide levels
• High throughput
• Simple operation
• Excellent carbide retention
• Low running costs
• High bond strength
• Very low porosity
• High performance quality coatings

Liquid fuel and oxygen are fed via a pre-mixing system and at high pressure into a combustion chamber where they burn to produce a hot, high-pressure gas stream. This is expanded through a laval type nozzle increasing the gas velocity to around 1500m/sec and the pressure to slightly above atmospheric. At this stage the powder can easily be injected into the gas stream.

This gas stream heats and accelerates the powder particles within the confines of the secondary nozzles so that they impact with tremendous energy upon the substrate material. The MET-JET System does not melt powders but only softens them. Because less heat is imparted to the particles and dwell times are very short, oxidation and decomposition are minimal in MET-JET coatings.

The Metallisation MET-JET System produces the densest metallic and carbide coatings of all, with high hardness and low oxide levels. Furthermore coatings are often compressively stressed allowing thick coatings to be applied without fear of spalling.

The Metallisation MET-JET System is designed to meet the needs of the general market by providing a robust, easy to use and inexpensive system.

The Metallisation MET-JET System comprises four main elements:

• The MET-JET gun
• The MET-JET mass flow meter controller
• PFII Powder feeder
• A cooling system

The whole system is integrated to provide reliable and reproducible results with easy to understand operation and a long life.

Interconnections between the various components have been designed such that it is almost impossible to make a wrong connection. Hoses are colour coded for ease of recognition and safety.

JET KOTE

The Jet Kote torch is based upon the tried and tested principle of the Jet Kote Torch Technology. The concentric injection of coating powder into the gas jet enable an optimum degree oat heating and a high degree of coating efficiency. Due to the simple construction method there are few wear parts that require servicing.

Therefore just a low level of maintenance costs is incurred in relation to the coating performance. The Jet Kote System is recognized worldwide for its aerospace quality coatings.

HIPO JET 2100

MSSA also offers the affordable and low process cost Powder HVOF System HIPOJET-2100 and the POWDER FEEDER PF-700.

The HIPOJET-2100 System along with the PF-700 Powder Feeder is a low cost HVOF system having high quality attributes. No cooling water required, hence heat exchangers & chilling systems are also not required.

The product runs on low cost fuels such as Propane / LPG / Propylene / Natural Gas and avoids Hydrogen, which is costly, and potentially an unsafe gas to use. As liquid fuels are not used, the system does not require any fuel pumps. The result is low operating cost compared to other HVOF systems.

The lightweight 1.45kg gun reduces operator fatigue and the powder feeding start switch is provided on the gun handle.

It offers simple operation because:

• It has no cooling water parameter to manipulate
• There are no run or ramp parameters to be set
• Operation & ignition of gun by a simple lever as on the conventional flame spray equipment

Any user capable of operating combustion spray equipment can operate HIPOJET-2100 system with minimal additional training.

Simple operation and low weight make the HIPOJET-2100 system along with PF-700 Powder Feeder excellent equipment for onsite thermal spray work.

The Hipojet-2100 high velocity oxy-fuel powder spray gun control console comprised of oxygen & fuel flow meters with control valves powder feeder, Model: PF-700&tm;.

Air Control Unit, comprised of automatic drain air filter with regulator and secondary Filter for oil.

High-pressure hose unit for oxygen, propane and air.

Optional:

• Water Cooled Jacket (Hybrid)
• Hipojet-2100 Extension (600 mm Long)

ECONOMICS OF HIPOJET SPRAYING

Deposit Efficiency (for guidance): 71% for WC-Co (on actual job condition)